Monoclonal antibodies identifying chick gonadal cells

1. The aim of the present study was to raise monoclonal antibodies (MAbs) which discriminate gonadal cell types in chickens.

2. A panel of 180 MAbs was generated, from which 14 were chosen for their specificity.

3. These MAbs were characterised immunohistologically on frozen sections of embryonic, newly‐hatched and adult, male and female, left gonads.

4. Three of these MAbs are described: AGC5, AGC7, and AGC13 which recognise respectively germinal epithelial cells, supporting cells and germ cells.

5. These MAbs may be useful in following the developmental pathways in the chicken gonad and analysing the interactive role(s) taking place between gonadal stromal cells and primordial germ cells.     

Production of an immune suppressor factor by Marek's disease lymphoblastoid cell lines

Culture fluids from Marek's disease (MD) lymphoblastoid cell lines have suppressive activity against normal and mitogen-stimulated chicken spleen and bursal cells and also against the homologous cell lines. Suppressive activity was also present in supernatants from spleen cells infected in vitro with MD virus. The suppressor factor from MD cell lines was non-sedimentable, trypsin sensitive, heat resistant and partially dialysable. Preliminary studies suggest it has a molecular weight of 20,000 daltons. Studies were also conducted on the effect of the prostaglandin inhibitors indomethacin and aspirin on the production and action of the suppressor factor. At low concentrations they have a stimulatory effect on the cell lines suggesting that they inhibit the effects of suppressor factor; however only small amounts of prostaglandin E2 were present in supernatants. Evidence was obtained that the suppressor factor may act indirectly by stimulating the production of prostaglandin by spleen cell cultures. The role of a suppressor factor in the immunosuppression observed in MD is discussed.     

Characterisation of a resource population of pigs screened for resistance to salmonellosis

The degree of resistance to Salmonella choleraesuis infection in a reference family purposely bred to map resistance genes was assessed. Aspects of the innate and specific immune system were studied to find a parameter that might predict the resistance of pigs to salmonellosis. The family was bred from commercial full-sister pairs of F1-gilts and four boars. One boar (G398) was identified as breeding susceptible offspring, and one boar (G402) as breeding resistant offspring on the basis of pyrexial responses and numbers of Salmonella in liver and spleen post mortem. The other two boars were classified as 'possible resistant' (Y2008) and 'unknown' (Y6101) respectively. Functional differences in immune cells (neutrophils and lymphocytes) between the offspring of G398 and G402 were detected. The most resistant piglets had a higher number of circulating neutrophils and better polymorphonuclear neutrophils (PMNs) function, but a lower mitogenic response of lymphocytes both pre- and post-infection and a lower antibody response. Between the offspring groups of Y2008 and Y6101 no differences were found in the number of viable Salmonella in liver and spleen at post mortem or in immune cell function, however, the survival rate of these offspring groups was clearly different. Twenty three percent of the Y2008-offspring and 33% of the Y6101-offspring reached the predetermined humane clinical endpoint before the end of the experiment. Our findings suggest a role for several inherited immunological traits, including PMN function and lecithin-induced mitogenic proliferation, which appear to influence resistance to salmonellosis.     

Use of ev loci as a measure of inbreeding in domestic fowls

1. The endogenous avian leukosis virus (ev) loci present in 9 lines of domestic fowls have been partially characterised and the average heterozygosity of the loci in each line calculated. 2. Using these data an estimate of the coefficient of inbreeding of the lines was derived; this estimate of the extent of inbreeding is compared with the mating history of the lines. 3. This method provides the first means of directly assessing the degree of inbreeding of fowl lines: assumptions implicit in the method are discussed.     

Genetics of resistance to coccidiosis: response of inbred chicken lines to infection by Eimeria tenella and Eimeria maxima

1. Experiments have been carried out to compare weight gain, mortality and oocyst production in 7 inbred and partially inbred lines of chickens after challenge with the coccidial parasites Eimeria tenella and E. maxima. 2. There were large differences between lines in the effects of challenge on weight gain and mortality for both species of parasite. However, the lines suffering the greatest mortality were not those showing the greatest effects on weight gain, indicating that mortality alone is not an adequate criterion in selection for resistance. 3. Although oocyst production differed between lines there was no correlation with mortality or with weight loss, implying that the variation observed in these traits was not due to a restriction of the parasite but to an accommodation of its effects. 4. Mortality and weight loss resulting from challenge with E. tenella in the different lines did not correlate with that caused by E. maxima. 5. There was evidence of an association of genes of the major histocompatibility complex genes with mortality, but not with weight loss or oocyst production: there was no indication of association of resistance to coccidiosis with resistance to Marek's disease.     

Genetics of resistance to Salmonella typhimurium in newly hatched chicks

1. A survey of inbred and partially inbred lines of chickens showed pronounced differences in mortality following challenge of the newly hatched chicks with Salmonella typhimurium. Lines W, 6(1) and N were highly resistant to challenge, whereas lines C and 15I were highly susceptible. 2. This difference in susceptibility was observed with a range of 5 strains of S. typhimurium of different degrees of virulence and also following both oral and intramuscular challenge. 3. The inheritance of resistance was studied in detail by examining a series of crosses between the susceptible line C and resistant line W. The pattern of mortality in crosses and back-crosses between these lines indicated resistance is dominant and was consistent with the inheritance of a dominant autosomal resistance gene. 4. There was no evidence of maternal effects in these crosses, and no evidence of association with the major histocompatability complex.     

Genetic differences in susceptibility to a mixture of avian infectious bronchitis virus and Escherichia coli

Two-week-old chickens of 9 inbred and partially inbred lines of chickens were challenged intranasally with a mixed infection consisting of a pool of virulent strains of infectious bronchitis virus and a pool of pathogenic strains of Escherichia coli. 2. Wide differences in mortality were observed in the different lines, ranging from 3% in a Brown Leghorn line to 87% in White Leghorn line 7(2). 3. Experiments involving challenge with E. coli alone or virus alone suggested that this variation reflected resistance to the virus rather than to E. coli. 4. Reciprocal F1 matings suggested these differences in mortality were not attributable to maternal effects and indicated that the inheritance of resistance was fully dominant. 5. The pattern of mortality in F2 and backcross progeny of matings was compatible with the inheritance of a dominant autosomal resistance gene and showed no evidence of association with the major histocompatibility complex.