Haemolytic complement activity,C3 and Factor B consumption in serum from chickens divergently selected for antibody responses to sheep red blood cells

Antibody responses, serum complement haemolytic activity, and complement component C3 and Factor B consumption were studied in chickens divergently selected for high and low antibody responses to sheep red blood cells, and in a randombred control line. Significantly higher total and IgG antibody responses to SRBC were found after intramuscular immunisation in the high antibody responder (H) line versus the low antibody responder (L) line and the control (C) line. Also significantly higher antibody titres were found in the C line as compared to the L line. Ca-dependent (classical) and Ca-independent (alternative) complement haemolytic activity was significantly higher in the H line than in the L line. Also initial complement haemolytic activity and C3 levels prior to immunisation with SRBC were significantly higher in the H than in the L line. The L line, on the other hand, showed numerically higher Factor B levels. Immunisation with SRBC was followed by a different consumption of C3 in serum of the H line than the L line.The results indicated that divergent selection of chickens for specific antibody responses to SRBC affected complement levels and C3 consumption in these chickens. This suggests a genetic linkage between these two immune traits.     

Comparison of the enzyme-linked immunosorbent assay and complement fixation test for detecting Brucella ovis antibodies in sheep

A solid-phase, indirect, enzyme-linked immunosorbent assay (ELISA) was compared with the microtitre complement fixation test for detecting Brucella ovis antibodies in 220 ram sera. The ELISA was more sensitive than the complement fixation test; it demonstrated antibodies in 11 sera from known infected or vaccinated rams that were complement fixation test negative. No false positives were recorded with the ELISA and, in 36 sera positive to both tests, the ELISA titres were consistently higher than the corresponding complement fixation test titres.     

Comparison of the dot-immunobinding assay with the complement fixation test for the detection of Brucella antibodies in sheep

A dot-immunobinding assay (DIA), using as antigen a sonic extract of Brucella abortus dotted on nitrocellulose bound to a plastic strip, was employed for the detection of Brucella antibodies in 666 sheep sera. The results were compared with the complement fixation test (CFT). All the 242 sera belonging to two flocks were found to be negative by DIA. CFT was negative in 239 cases, whereas three samples showed anti-complementary activity. Of the 424 sera from the remaining three flocks, 98 were positive by both tests and six were positive in DIA, but negative in CFT. In addition, 14 of the 19 anti-complementary sera were also positive by DIA.     

Prolactin assay for fescue toxicity in sheep

Fungal endophyte (Acremonium spp.) toxicity affects sheep and cattle grazing a number of forages, including ryegrasses (Lolium spp.) and tall fescue (Festuca nrundinacea). The endophyte in tall fescue is responsible for ill thrift, as indicated by low weight gains or weight loss⁽¹⁾ and decreased reproductive efficiency⁽²⁾, and is associated with increased body temperatures. Extensive research has been undertaken in the USA to determine ways of reducing the impact of fescue toxicity on the beef industry⁽³⁾, whilst New Zealand research is directed toward both ryegrass and fescue endophyte toxicity and its impact on sheep⁽⁴⁾⁽⁵⁾ and cattle⁽⁶⁾ production. Much of this work involves field evaluations of productive performance in animals fed toxic and non-toxic forage, so that it is important to be sure that treatment effects are due to the endophyte.     

A hemolytic assay for the measurement of equine complement

A hemolytic assay was developed for the measurement of functional equine complement activity. The assay utilizes antibody sensitized chicken erythrocytes as the target cell and was specific for classical pathway (antibody dependent) complement activity. The assay was found to be reproducible and more sensitive than previous reports using other species of target cells. Total serum complement (CH50) values were determined for five mares and their foals and followed over a period of 3 months.     

Haemolytic crisis in sheep as a result of chronic exposure to copper

Usually practicing veterinarians and animal keepers have to deal with inadequate supplementation of copper which causes deficiency diseases. However, instead of curing, the consequential intake of copper is likely to cause copper intoxication. Copper poisoning is observed particularly frequently, in sheep--the most sensitive domestic animal to copper toxicity. In most cases, sheep undergo chronic exposure to copper causing liver necrosis and resulting in massive haemolysis, haemoglobinuria and eventually in renal failure. The observed symptoms have an acute character and a set of them is called haemolytic crisis. The pathogenesis, signs and diagnosis of this syndrome are described in this article.     

Anti-complementary activity for guinea-pig and sheep complement in serum and Mg2+-EGTA plasma from various animals

Serum and Mg²⁺-ethyleneglycoltetraacetic acid (EGTA) plasma from 14 domestic or laboratory animal species had no anti-complementary activity for sheep complement (C). Serum samples from 8 species and all 14 Mg²⁺-EGTA plasma samples were anti-complementary towards guinea-pig C. Thus, use of sheep C in a warm complement fixation text (with human erythrocytes sensitized with sheep antiserum, IgM, slow or fast γ-globulin antibody), in the presence or absence of Mg²⁺-EGTA, may be a satisfactory method of eliminating anticomplementary activity.     

A simple hemolytic assay for bovine complement component C3

A simple, one-step, alternative pathway (AP) hemolytic assay for bovine C3 has been developed. Methylamine was used to prepare a bovine serum reagent, R3, functionally depleted of C3. The addition of purified bovine C3 to the R3 reconstituted, in a dose-dependent manner, the hemolytic activity for unsensitized heterologous erythrocytes. The assay was used to determine relative levels of C3 in different bovine serum samples. Human C3 and bovine C3 were interchangeable in the assay. Reconstitution of bovine and human R3 reagents with homologous or heterologous C3, in the presence of different species of erythrocytes, provided evidence that cell surface regulation of the homologous hemolytic AP may not be limited to the assembly and activity of the C3 convertase. The AP assay was more sensitive and less complex to perform than a standard classical pathway assay for bovine C3.     

Radioreceptor assay for determination of xylazine and medetomidine in sheep plasma

A radioreceptor assay technique is described for the measurement of xylazine and medetomidine in sheep plasma. The assay was based on the displacement of tritiated clonidine from a 2-adrenoceptors in a rat brain homogenate by xylazine or medetomidine extracted from plasma. Plasma samples from sheep which had been given xylazine and medetomidine were treated with alumina to remove endogenous catecholamines which would otherwise have bound to α₂-_- adrenoceptors and interfered with the assay. The drugs were then extracted using chloroform, reconstituted in buffer and used to displace [³H]clonidine. The concentration of α₂-agonist was calculated by reference to standard curves. The method had a detection limit of 2.5 ng/mL for xylazine and 0.24 ng/mL for medetomidine. The assay could also be used to detect metabolites capable of binding to α₂-receptors.