Peripheral Blood Lymphocyte Subpopulations and Immunoglobulin Concentrations in Healthy Foals and Foals with Rhodococcus equi Pneumonia

Infectious diseases are common in foals aged 1-5 months. The objectives of this investigation were to evaluate immunologic parameters in foals from birth to weaning to establish reference values for the proportion of circulating lymphocytes that were helper (CD4+) or cytotoxic (CD8+) T cells, or B cells; to measure serum immunoglobulin (IgM and IgG) concentrations; and to compare these immunologic parameters to values in foals with naturally occurring Rhodococcus equi pneumonia and in adult horses. Peripheral blood lymphocyte subpopulations were determined by flow cytometric analysis, and serum IgG and IgM concentrations were determined by radial immunodiffusion. Flow cytometric analysis of lymphocyte subpopulations suggested age-related changes in the cell-mediated immune system in horses. Absolute circulating CD4+ and CD8+ T lymphocytes and B cells increased linearly up to 3 months of age. Circulating B cell concentrations from birth to 6 months of age were greater than values in adult horses and the lymphocyte differences among the age groups are mainly due to variation in B lymphocytes. Both absolute and proportional B cell concentrations were greater in foals with R equi pneumonia than in healthy foals at the same age. The increase in absolute cell counts of each subpopulation was dependent on the increase of absolute peripheral blood lymphocyte count. Serum IgG concentration increased linearly from 1 to 3 months of age, and serum IgM concentrations increased from 1 to 6 months of age. These data suggest age-dependent cell-mediated and humoral development in young foals.     

Peripheral Blood Neutrophil Function and Lymphocyte Subpopulations in Cycling Mares

The purpose of this study was to evaluate different parameters of the immune status in the mare, during the follicular and the luteal phases of the oestrous cycle, in two consecutive years. Functional competence of peripheral blood neutrophils, such as chemotaxis, phagocytosis and oxidative burst was assessed under physiological cyclic conditions (Exp. I). In the second year of this study (Exp. II), besides peripheral blood neutrophil phagocytosis and oxidative burst analysis, circulating lymphocyte subsets were also characterized. The reproductive status in a total of 17 adult cycling mares was evaluated by ultrasonography and further confirmed by plasma progesterone levels. Chemotaxis tests were performed using porous membranes inserted in transwell chambers. Lipopolysaccharide (LPS) from Escherichia coli and N‐formyl‐Met‐Leu‐Phe (fMLP) were used as chemoattractants. Measurement of phagocytosis and oxidative burst in blood neutrophils were assessed by flow cytometry using commercially available kits. Quantification of T‐lymphocyte subsets was assessed by indirect immunofluorescence staining after incubation with monoclonal antibodies specific for CD2, CD3, CD4 and CD8 cell markers by flow cytometry. Natural killer cells and B cells were estimated mathematically. No significant difference was found in migration, phagocytosis and oxidative burst at either phase of the oestrous cycle. Statistical analysis of total white blood cell counts also showed no significant difference between either phase of the oestrous cycle, although there was a tendency for blood neutrophils to increase in number under the progesterone influence (p = 0.09). Lymphocytic subpopulations did not differ throughout the oestrous cycle. Overall, our results suggest that luteal and follicular phases in cycling mares may not influence the immune status of the mare.     

Effect of plasma transfusion on neutrophil function in healthy and septic foals

OBJECTIVE: To evaluate the effect of plasma transfusion on phagocytosis and oxidative burst activity of peripheral blood neutrophils from healthy and septic equine neonates with sub-optimal passive transfer of maternal immunity. ANIMALS: Nine healthy and seven septic foals with suboptimal passive transfer of maternal immunity (serum IgG < 8 g/L) presented to participating veterinary hospitals for plasma transfusion, and seven healthy foals less than 7 days of age and with circulating IgG concentrations > or = 8 g/L. PROCEDURE: Foals with serum IgG concentrations < 8 g/L were assessed as healthy or septic. Sepsis was recognised by positive bacterial cultures and/or sepsis scores of > or = 11. All foals received between 1 and 3 L of plasma to boost circulating IgG concentrations to > or = 8 g/L. Serum IgG concentrations were determined before and following transfusion by glutaraldehyde coagulation test and confirmed by single radial immunodiffusion assays. Neutrophil phagocytosis and oxidative burst activity were determined before plasma transfusion and at 0 h, 12 h, 24 h, 48 h and 5 d following treatment. Neutrophil function from seven healthy foals less than 7 d of age and with circulating IgG concentrations of > or = 8 g/L was similarly evaluated on a single occasion. RESULTS: Plasma treatment significantly increased circulating IgG concentrations for healthy and septic foals. Oxidative burst activity of neutrophils from septic foals was significantly increased 5 days following treatment, relative to 0 h post treatment. Other differences were not significant but suggested a transient decrease in phagocytosis by neutrophils from healthy foals and increased phagocytosis by neutrophils from septic foals immediately following transfusion. Oxidative burst activity of neutrophils from septic foals tended to be less than that of healthy foals at all sampling times. Serum IgG concentrations were not correlated with neutrophil phagocytosis, but were correlated with oxidative burst activity. CONCLUSIONS: Plasma transfusion did not improve neutrophil function of healthy foals, suggesting that such treatment may be of equivocal benefit for healthy neonates. Conversely, improved neutrophil function was observed following treatment of septic foals, suggesting that plasma transfusion was beneficial for these foals. Oxidative burst activity of neutrophils from septic foals was lower than that of neutrophils from healthy foals and was significantly improved 5 days post treatment, when compared with values obtained immediately following treatment.     

Seasonal reproduction in the mare: possible role of plasma leptin, body weight and immune status

The primary objective of this study was to evaluate the possible role of leptin, body weight and immune status on reproductive activity throughout the transition period from cyclicity to seasonal anestrus, during anestrus and resumption of ovarian activity in Lusitano mares. Mares in good body condition were monthly monitored throughout 2 years (10 mares in each year) for evaluation of their reproductive status by sequential ultrasonography and plasma progesterone determinations. On the second year, all mares were weighed. Progesterone and leptin were assayed by radioimmunoassay (RIA). Parameters of the immune status (phagocytosis and oxidative burst of neutrophils, characterisation of circulating lymphocyte subsets) were also evaluated. Phagocytosis and oxidative burst in blood neutrophils were measured by flow cytometry using commercially available kits. Lymphocyte subsets were assessed by indirect immunofluorescence staining after incubation with monoclonal antibodies specific for CD2, CD19, CD4, CD8 cells markers by flow cytometry. Natural killer cells and B cells were estimated mathematically. No significant difference was found in phagocytosis, oxidative burst and circulating lymphocyte subsets at anestrus and at either phase of the estrous cycle (p>0.05), suggesting that the immune status of the mare was not influenced by the seasonal changes in ovarian activity. This study also suggests that body weight has a direct relationship with plasma leptin levels. Increased concentrations of this hormone in circulation might be associated with the restart or maintenance of ovarian cyclicity in Lusitano mares.     

A comparison of foal and adult horse neutrophil function using flow cytometric techniques

Flow cytometric assays were used to compare phagocytic and oxidative burst activity of neutrophils from healthy foals less than 7 days of age with the activity of cells from healthy adult horses. The phagocytosis of Staphylococcus aureus by foal neutrophils was less than that observed for adult neutrophils when autologous serum was used as the source of opsonins in the assay. The use of adult serum did not significantly improve the ability of foal neutrophils to attach bacteria. The oxidative burst activity of foal neutrophils was equivalent to that of adult cells. However, when serum or plasma was incorporated into the oxidative burst assay, foal neutrophils demonstrated greatly reduced autofluorescence and a suppressed response to phorbol myristate acetate (PMA), relative to that demonstrated by adult cells. These results suggest that peripheral blood neutrophils from foals have a reduced ability to phagocytose bacteria relative to that exhibited by adult horse neutrophils and that the oxidative burst activity of foal neutrophils is down-regulated in response to an unidentified serum factor(s). Such changes may contribute to the increased susceptibility of foals to septic disease.     

Effects of training on resting peripheral blood and BAL-derived leucocyte function in horses

In this study, the effects of prolonged, high intensity training on aspects of peripheral blood and bronchoalveolar lavage (BAL)-derived leucocyte function were evaluated in 8 horses. All horses undertook a 7 week endurance training programme, followed by 5 weeks of high intensity training (HIT). Thereafter, horses were divided into control (C) and overtraining (OT) groups. The frequency and intensity of training were increased more substantially for horses in the OT group. Training was terminated in week 32 when horses in the OT group demonstrated a significant performance reduction. Peripheral blood and BAL samples were collected from 4 horses in C and OT groups in training weeks 7, 11, 14, 18, 22, 28 and 32. Flow cytometric techniques were used to assess phagocytosis by peripheral blood neutrophils and pulmonary alveolar macrophages (PAM), and oxidative burst activity of neutrophils, PAM, peripheral blood and BAL-derived lymphocytes. Peripheral blood neutrophil phagocytosis (internalisation) increased during the initial HIT period and decreased from week 16 when the training workload was increased for both groups. The oxidative burst activity of peripheral blood neutrophils and lymphocytes similarly increased and then decreased in response to training. The oxidative burst activity of PAM was reduced towards the end of the overtraining phase of the programme. Pulmonary alveolar macrophage phagocytosis and oxidative burst activity of BAL-derived lymphocytes demonstrated no change throughout the course of the study. There was no difference in results obtained from C or OT group horses, suggesting that protracted HIT, rather than overtraining, was associated with impaired cell function. The detrimental effects observed in peripheral blood neitrophil and PAM function may indicate impaired nonspecific immunity which may adversely affect the health and performance of horses undergoing protracted periods of intense training.     

Primary and anamnestic responses of bovine bronchoalveolar and peripheral blood lymphocyte subsets to aerosolized Pasteurella haemolytica A1

Site-specific responses of bronchoalveolar and peripheral blood lymphocyte subsets were compared during primary and anamnestic immune responses against live Pasteurella haemolytica A1 (Ph1). Eight 1-year old calves were sequentially exposed intrabronchially with aerosolized Ph1 on days 0, 14, and 21, and two calves were sham exposed. Bronchoalveolar and peripheral blood lymphocytes were analyzed before each Ph1 exposure, and on days 3 and 7 post exposure using single and two-color flow cytometry to identify CD2+, CD4+, CD8+, CD21+, CD45R+, CD25+ and gammadelta lymphocyte subsets. Significant differences (p < 0.05) in bronchoalveolar and peripheral blood lymphocyte subsets were observed before Ph1 exposure. Subsequent aerosol exposures, resulted in significant (p < 0.05) changes in bronchoalveolar lymphocyte subsets and the CD4:CD8 bronchoalveolar lymphocyte ratio, but concomitant changes were not observed in peripheral blood lymphocytes. Expression of CD2, CD4 and CD8 lymphocyte differentiation antigens was consistently lower and more heterogeneous on bronchoalveolar lymphocytes. Differential analysis of bronchoalveolar leukocytes revealed a significant increase in bronchoalveolar lymphocytes and neutrophils during anamnestic responses.     

The effect of high intensity exercise on the functional capacity of equine pulmonary alveolar macrophages and BAL-derived lymphocytes

The effect of strenuous exercise on the functional capacity of pulmonary alveolar macrophages (PAM) and bronchoalveolar lavage-derived lymphocytes was determined in eight horses prior to and after 7 weeks of training. Strenuous exercise had no effect on the total cell count or the percentage of live cells in bronchoalveolar lavage (BAL) samples prior to or following training. However, training was associated with a significant increase in the total cell count of pre-exercise BAL samples and a significant reduction in the percentage of live cells in post-exercise samples. Strenuous exercise was associated with impaired phagocytosis by PAM after 7 weeks of training but had no effect on similar samples obtained from untrained horses. The oxidative burst activity of PAM was significantly increased following strenuous exercise for both untrained and trained horses. BAL -derived lymphocyte oxidative burst was similarly affected following training. These results suggest that strenuous exercise and training may influence pulmonary immune cell function.     

Immunologic Profiles of Peripheral Blood Leukocytes and Serum Immunoglobulin G Concentrations in Perinatal Mares and Neonatal Foals (Heavy Draft Horse)

The purpose of this study was to examine sequential changes in the immunologic parameters of perinatal mares and neonatal foals of the heavy draft horse. Blood samples were collected from clinically healthy pregnant mares and their newborn foals every week from 1 month before the expected foaling date, and 1 hour, 1 day (24-48 hours), and 1, 2, 3, and 4 weeks after foaling. Peripheral blood samples were used to examine total leukocyte counts (n = 20), differential leukocyte counts (n = 20), lymphocyte subpopulations (n = 13), lymphocyte responses to mitogens (n = 10), neutrophil phagocytic function (n = 12), and serum immunoglobulin G (IgG) concentrations (n = 10). In perinatal mares, remarkable changes observed included increased neutrophils, decreased lymphocytes, decreased CD4⁺ T lymphocytes, and decreased lymphocyte responses to mitogens at delivery. These changes were speculated to be the result of physical stress associated with delivery. In neonatal foals, increase in the phagocytic function of neutrophils, and increase in serum IgG concentration after suckling colostrum and increase of lymphocytes accompanied by physiologic growth were observed. Compared to dams, foals showed lower phagocytic function of neutrophils before suckling and fewer lymphocytes and lower lymphocyte responses to mitogens within 1 day after birth. This study revealed immunologic dynamics in perinatal mares and neonatal foals. Immunologic functions are suppressed in foaling mares and are immature in neonatal foals, especially before colostral intake. We expect these data will be useful for further studies in the field of clinical immunology, and preventive medicine.     

Age-related changes in lymphocyte subsets of quarter horse foals

OBJECTIVE: To characterize changes in lymphocyte subsets over time in foals from birth to 18 weeks of age, accounting for differences among individuals, and to determine the effect of overnight storage of blood samples on foal lymphocyte subset concentrations. ANIMALS: 8 healthy Quarter Horse foals from birth to 18 weeks of age. PROCEDURE: Blood samples were collected longitudinally from birth to 18 weeks of age and a CBC performed on each sample. The samples were stained for lymphocyte markers, either immediately or after overnight storage and analyzed by flow cytometry. RESULTS: Total leukocytes, total lymphocytes, and the absolute concentrations of all lymphocyte subsets increased significantly with age. The proportions of B29A+, CD21+, and-equine major histocompatability complex class-II molecule+ lymphocytes increased significantly with age. The proportion of equine (Eq) CD5+, EqCD8+, and EqWC4+ lymphocytes decreased significantly with age. Significant differences among foals were found with respect to initial concentrations with respect to initial concentrations, but not with respect to the rate of increase of the various subsets tested. Significant differences were not found in subset values when comparing blood samples stained on the day of collection or after overnight storage at room temperature (approx 21 C) or under refrigeration. CONCLUSIONS AND CLINICAL RELEVANCE: These results are consistent with an increase in subset numbers and proportions over time, but with individual differences among foals. The observation of individual differences in subsets among foals suggests that there may be individual differences in susceptibility to infectious disease during the perinatal period. The absence of an effect of overnight storage makes field studies of lymphocyte subset concentrations more feasible.     

Simultaneous Flow Cytometric Analysis of Phagocytosis and Oxidative Burst Activity in Equine Leukocytes

This paper describes a method for simultaneously measuring phagocytosis and oxidative burst activity in equine peripheral blood leukocytes by flow cytometry. Opsonized propidium iodide-labelled Staphylococcus aureus (PI-Sa) was used to measure the uptake of bacteria by equine phacocytes and the oxidative burst activity by oxidation of dihydrorhodamine 123. The requirements to achieve optimal activity of phagocytosis and oxidative burst are described. The advantage of the simultaneous technique is that it provides both independent and comparative values for phagocytosis and the oxidative burst, for the detection of impaired mechanisms of microbial destruction. Furthermore, the technique allows evaluation of opsonization activity in this context.     

Modulation of leukocyte populations and immune responses in sheep experimentally infected with Anaplasma (formerly Ehrlichia) phagocytophilum

Anaplasma phagocytophilum infection in sheep is characterized by an immune suppression as indicated by impaired antibody response, reduced lymphocyte response and reduced oxidative burst. The effect of A. phagocytophilum infection on leucocyte populations, especially lymphocytes, was therefore investigated in six sheep experimentally infected with A. phagocytophilum, and compared with leucocyte populations from control animals.To investigate the ability of the infection to interfere with the cellular and humoral responses to specific antigens, the animals were vaccinated with commercial vaccines at the time of experimental infection, and monitored for 56 days.There were reduced percentages of gammadelta T-cells and CD4+ T-cells in peripheral blood of infected animals throughout the study period, and these cell populations showed a down-regulation of CD25 expression; while there was a relative increase in CD8+ T-cells. The reduction in CD25+ gammadelta T-cells involved a subpopulation of WC1+ gammadelta T-cells. During the first 2 weeks of the study there were reduced percentages of B-cells and leukocytes expressing MHC II and CD11b, though this decrease changed to a relative increase later in the study. The relative reductions in leucocyte populations corresponded with the observed leucopenia during the first 3 weeks post-infection, which involved lymphocyte, neutrophil and eosinophil subsets [Vet. Immunol. Immunopathol. 86 (2002) 183]. There was a reduced expression of CD11b and CD14 on granulocytes during the first 2 weeks of the study, which corresponded with the previously reported leucopenia involving neutrophils and eosinophils. Antibody responses to vaccines, lymphocyte in vitro proliferative responses to antigens and mitogens, and in vitro IFN-gamma responses to antigens were reduced up to 4 weeks after infection.     

A modified live PRRSV vaccine and the pathogenic parent strain induce regulatory T cells in pigs naturally infected with Mycoplasma hyopneumoniae

Rhodococcus equi is an important respiratory pathogen of young foals for which a vaccine has long been sought. Two major impediments to effective vaccination are the functionally immature type I immune responses of neonatal foals and early exposure to the bacterium via the environment. Despite these obstacles, it appears that under specific circumstances foals can develop a protective immune response. In this study we investigated the protective mechanisms behind oral inoculation of foals with virulent R. equi bacteria. Two foals receiving an oral inoculum demonstrated accelerated development of R. equi specific cytotoxic T lymphocytes (CTL) as evidenced by significant lysis of R. equi infected, ELA-A mismatched cells at 3 weeks of age. As in a previous study, CTL were not detected until 5-6 weeks of age in two control foals. At each time point the ability of foal peripheral blood mononuclear cells (PBMC) to produce IFN-γ following stimulation with live R. equi or extracted cell wall lipids was similar to that of an adult horse control and between foals, regardless of treatment. These results provide a potential mechanism of protection which has previously been shown to occur following oral inoculation, and suggest that the early detection of CTL may be a useful marker for induction of protective immunity.     

Effects of midazolam on equine innate immune response: a flow cytometric study

Benzodiazepines (BDZ) are among the most frequently used class of psychotropic drugs employed in veterinary medicine in Brazil and worldwide due to their anxiolytic, muscle relaxant and anticonvulsant effects [J. Clin. Pharmacol. 33 (1993) 124]. Peripheral benzodiazepine receptor (PBR) sites were described in peripheral organs, endocrine steroidogenic tissues and immune organs and cells. Midazolam is a mixed-type agonist of PBRs. The present study is focused on the effects of midazolam on equine peripheral blood neutrophils, peritoneal macrophages and cortisol levels in plasma. Adult horses were treated with a single dose of midazolam (0.06 or 0.1 mg/kg) or with 0.9% NaCl. Immune cells were collected 24 h after treatment for flow cytometry analysis of Staphylococcus aureus-induced phagocytosis and oxidative burst. Plasma cortisol concentration was measured 30, 90, 180 and 360 min after midazolam treatment. Midazolam induced a dose-dependent reduction on: (1) peripheral blood neutrophil and peritoneal macrophage oxidative burst; (2) the capacity of both peripheral blood neutrophils and peritoneal macrophages to phagocyte S. aureus. Increments on plasma cortisol concentration were not found after 0.06 and 0.1 mg/kg of midazolam. The effects on oxidative burst of neutrophils and macrophages from horses treated with midazolam were interpreted as a consequence of an impairment of S. aureus-induced phagocytosis. The present data suggest that midazolam, most probably acting on PBRs present on equine macrophage and neutrophil membranes, might have changed some mechanisms related to both phagocytosis and oxidative burst. These results support the use of flow cytometry to identify functional properties and dysfunction of equine immune cells. They also confirm the notion that changes in the functional capacity of the immune system may represent an important hazard of exposure to drugs or chemicals.     

In utero infection with PRRS virus modulates cellular functions of blood monocytes and alveolar lung macrophages in piglets

The putative immunosuppressive effect of PRRS virus (PRRSV) on innate immune responses was studied in piglets infected in utero with PRRSV. Phagocytosis and oxidative burst capacities in 2-, 4- and 6-week-old in utero infected piglets were investigated and compared with age-matched control piglets. Phagocytic capacity of blood monocytes against Salmonella bacteria was investigated by flow cytometry. Oxidative burst in blood monocytes and in alveolar lung macrophages was investigated by luminol- and lucigenin-enhanced chemiluminescence, respectively. Decreased phagocytosis against Salmonella was found in blood monocytes from 4- and 6-week-old infected piglets compared to controls. In contrast, 2-week-old infected piglets showed phagocytic responses comparable to age matched control piglets. While oxidative burst capacity was increased in blood (PBMC) from in utero PRRSV infected piglets, the oxidative burst capacity of alveolar lung macrophages was decreased, especially in 2- and 4-week-old piglets, compared to age-matched control piglets. The present results indicate that in utero infection with PRRSV inhibits phagocytosis against Salmonella in blood monocytes as well as the oxidative burst capacity of alveolar macrophages. These observations indicate that PRRSV in utero infection induces at state of immunosuppression in piglets paving the way for enhanced secondary infections.     

The Effects of Selenium Source on Measures of Selenium Status of Mares and Selenium Status and Immune Function of Their Foals

The effect of organic and inorganic sources of selenium (Se) on measures of Se status of mares and their foals, Se concentrations of colostrum and milk, and indices of immune function of foals was studied. Twenty late-gestation Standardbred mares were randomly assigned to one of two groups. All mares received an identical balanced ration, except for the source of supplementary Se: one group received organic Se (Se yeast) and the other group received inorganic Se (sodium selenite), fed to deliver 0.3 mg/kg supplementary Se based on total ration dry matter. Mares received the experimental diet from 2 months before estimated due date until 1 month after foaling. Source of Se did not affect Se concentrations in maternal plasma, red blood cells, colostrum, or milk. At 1 month of age, foals from mares fed organic Se had higher red blood cell Se concentration than foals from mares fed inorganic Se (P < .05). Measures of immunity included serum immunoglobulin G concentration, lymphocyte proliferation in response to concanavalin A, and relative cytokine gene expression of stimulated lymphocytes (interferon gamma [IFNγ], interleukin [IL]-2, IL-5, IL-10, tumor necrosis factor alpha [TNFα]) and neutrophils (IL-1, IL-6, IL-8, IL-12, TNFα). Relative gene expression of IL-2, TNFα, and IFNγ by foal lymphocytes was associated with the source of Se supplementation provided to the mares. We conclude that the source of dietary Se provided to mares may influence the immune function of foals at 1 month of age through changes in relative gene expression of certain lymphocyte cytokines.     

Effects of feeding intensity during the dry period on leukocyte and lymphocyte sub-populations, neutrophil function and health in periparturient dairy cows

The objective of this investigation was to study (1) the numbers of leukocytes, (2) the proportions of lymphocytes expressing CD4, CD8, WC1, B or IL2R and (3) neutrophil phagocytosis and oxidative burst activity in blood around parturition in three groups of dairy cows fed different levels of a total mixed ration during the last eight weeks before calving. All cows were fed ad libitum during the first eight weeks of lactation. Serum concentration of the acute phase protein serum amyloid A (SAA), the milk somatic cell count (SCC) and disease incidence were also recorded. Special emphasis was given to the weeks just before and just after calving as dairy cows are known to be immune suppressed during this period. Dry period diet had only minor effects on leukocyte numbers, and did not influence neutrophil phagocytosis and oxidative burst. In addition, no effect was observed on disease incidence or SAA concentrations. However, an increase in the proportion of B-lymphocytes and a decrease in the proportion of WC1+ T lymphocytes were observed after calving in cows fed high or low energy rations during the dry period, but not in cows fed a medium energy ration. The weeks just before and after parturition were characterised by neutrophilia, eosinopenia, lymphopenia and monocytosis, but time had no effect on neutrophil phagocytosis and oxidative burst. The proportions of CD4+, CD8+, B+ and IL-2R+ lymphocytes increased in early lactation relative to the mid dry period. In addition, the concentration of SAA increased dramatically at calving. The results emphasise the need for more studies to clarify the complex interactions between nutrition and immunity during the peripartum period in dairy cattle.     

Lymphocyte subpopulations in spontaneous disease of rhesus macaques.

The immunologic status of rhesus macaques (Macaca mulatta) with naturally occurring disease was evaluated by determining the percentages of B and T lymphocytes and mitogen responsiveness of lymphocytes in peripheral blood and lymph nodes. The B lymphocytes were identified by the presence of cell surface immunoglobulin and receptors for complement. The T lymphocytes were identified by their ability to form spontaneous rosettes with sheep red blood cells. Rhesus macaques with idiopathic or primary amyloidosis had normal lymphocyte characteristics. Peripheral blood lymphocytes from rhesus macaques with atypical tuberculosis had decreased percentages of spontaneous rosette-forming cells and depressed responses to concanavalin A, and those with chronic diarrhea or chronic arthritis were also found to have abnormal peripheral blood lymphocyte characteristics. The percentage of B and T lymphocytes in normal lymph nodes was variable, making simultaneous histologic examination necessary for evaluation of diseased animals.     

Effects of road transportation on lymphocyte subsets in calves

The effect of transportation on peripheral blood lymphocyte subsets in 24 calves was investigated by flow cytometry. Blood was collected before departure, on arrival, at 24h and 1 week after arrival. Highest leucocyte and neutrophil counts, associated with increased concentrations of cortisol and catecholamines, indicated that stress was maximal upon arrival. At this time, a decrease in the percentages of all T lymphocyte subsets was evident, while they did not decrease as absolute counts. The proportion of CD21(+) cells did not change, indicating that the relative reduction of T lymphocyte subsets was not related to an increase in B lymphocytes. These variations may be due to the increase of a natural killer (NK) cell subset. NK cell expansion, together with increasing lymphocyte count and increasing major histocompatibility complex class II expression, may indicate stress-induced stimulation of the immune system.     

Blood and milk cellular immune responses of mastitic non-periparturient cows inoculated with Staphylococcus aureus

Lymphocyte function and phenotype of peripheral blood and mammary gland cells were evaluated in non-periparturient cows before and at 1, 4 to 8 and 9 to 14 d after inoculation with Staphylococcus aureus, as expressed by percentage of CD3+, CD2+, and CD45R+ cells, antigen density of these markers per lymphocyte, and mitogen-induced blastogenesis. Milk bacterial counts and somatic cell counts (SCC) were also assessed. Mitogen-induced blastogenic responses were strong in blood and weak in mammary gland cells in all observations and positively correlated with the percent of CD45R+ cells. Significantly greater percentages of milk CD3+ lymphocytes and increased CD3, CD2, and CD45R antigen density per cell were observed after challenge. The blood CD3 and CD2 antigen density per lymphocyte and the milk CD2+ lymphocyte percent were negatively correlated with SCC (P ≤ 0.01). No mastitis (SCC ≤ 500 000 cells/mL) was observed in cows showing blood lymphocyte CD2 and CD3 antigen density indices ≥ 2.5 and 6, respectively. Forty-one percent of SCC values were predicted by the combined blood CD2 and milk CD3 antigen density (P ≤ 0.01). These findings support the hypotheses that mitogen-induced lymphocyte blastogenesis is not a valid test to assess mammary gland immunocompetence and that CD2 expression may facilitate immune responses by decreasing the number of T cell receptors required to achieve full activation.