Resistance to a malignant lymphoma in chickens is mapped to subregion of major histocompatibility (B) complex.

A genetic recombinant within the major histocompatibility (B) complex of the chicken has revealed the chromosomal subregion effecting resistance to Marek's disease--a malignant lymphoma induced by a herpesvirus. The recombinant, BF21-G19, occurred spontaneously among the progeny of a male heterozygous for resistant BF21-G21 and susceptible BF19-G19 haplotypes. Exposure to Marek's disease of families segregating for the recombinant showed that this new F-G arrangement conferred a level of resistance equivalent to that of the resistant parental haplotype. Thus, a gene, or genes, within or closely linked to the B-F region of the B complex appears to be responsible for the observed resistance to Marek's disease.

Cellular expression of MHC glycoproteins on erythrocytes from normal and aneuploid chickens.

The major histocompatibility complex (MHC) in the chicken (B-complex) encodes glycoproteins homologous in function and distribution to the mammalian MHC. These are the B-F (class I) and B-L (class II) glycoproteins. In addition, a third glycoprotein (B-G) is also encoded by the chicken MHC. We are interested in examining gene regulation and cellular expression of these MHC gene products in the chicken. The trisomic line of chickens is being developed as an animal model for this purpose. Birds from this line contain either 2, 3, or 4 MHC-encoding chromosomes. In this study, we investigated the hypothesis that the quantities of B-complex glycoproteins on the membranes of fully differentiated erythrocytes are proportional to the number of MHC-encoding chromosomes present in particular birds. Hemagglutination final titer and quantitative adsorption assays were carried out using erythrocytes from disomic and aneuploid chickens homozygous for the B15 haplotype. The average hemagglutination final titers were higher for tetrasomic cells as compared to disomic cells. Furthermore, in adsorption assays, employing a B15 cross-reacting alloantiserum, trisomic and tetrasomic erythrocytes displayed increased adsorption capabilities (1.6 and 3.1 fold, respectively) compared to disomic control cells. These results indicate a step-wise increase in the amounts of erythrocyte surface glycoproteins per cell in the trisomics and tetrasomics, respectively. Such findings are consistent with a MHC-dosage-dependent model of gene expression in homeothermic vertebrates.

Genetics and classification of major histocompatibility complex antigens of the chicken.

The chicken MHC consists of a gene complex divisable into three chromosomal regions, each producing a series of genetically antithetical molecules with regionally specific functions. Most of the genes (alleles) of each region are present in unique haplotype combinations with genes (alleles) from the other two regions; relatively few haplotypes appear to share identical regional genes. Even with the high degree of polymorphism existing within and between regions, general typing of erythrocytes for MHC haplotypes can still be performed as economically as ever with alloimmune reagents of known specificity.

Immunogenetics of the A-E alloantigen complex.

The close linkage (0.5%) between the A and E erythrocyte alloantigen loci present a special challenge in the production of locus-specific typing antisera. The objective of the investigation was to determine immunogenetically the A-E haplotypes (genetically linked combinations of A and E antigens) existing in the locally maintained individuals of the New Hampshire (NH) and White Plymouth Rock (WR) breeds. The A and E alloantigens in these populations were identified using reference antisera previously produced in White Leghorns. A total of four A-E haplotypes were identified within each of the two breeds; A2E1, A6E2, A6E4, and A8E2 in WR and A2E1, A3E7, A7E4, and A8E2 in NH. Individuals of these two brown-egg breeds were backcrossed over several generations to a line of Ancona chickens homozygous at the A and E loci. Genetic segregation occurring over four generations resulted in nonrecombinant and recombinant progeny that were immunized reciprocally with the blood of siblings to raise antibodies reactive with the individual A and E antigens of the NH and WR stocks. The antisera resulting from the within-family alloimmunizations confirmed the haplotypes deduced in the WR and NH lines from the initial tests with the A and E reference antisera.

Further tests for genetic linkages of three morphological traits, three blood groups, and break points of two chromosome translocations on chromosome one in the chicken.

Two matings were conducted to further test the locations of the pea comb (P*), blue egg shell color (O*), and tardy feathering (T*) loci. In each mating a different chromosome rearrangement break point (R(B)) was tested against the three loci. Independent segregation was noted between the traits and the R(B) when the R(B) was on the long arm of chromosome 1. Significant linkage was noted when an R(B) on the short arm was tested against the three markers, indicating that the loci for P*, O*, and T* are on the short arm. Three blood group loci, EAD*, EAI*, and EAP*, were simultaneously tested against the short arm R(B). Independent segregation was noted in each instance, indicating that these blood group loci are not on the short arm of chromosome 1.

Response of major histocompatibility (B) complex haplotypes B22, B26, and B30 to Rous sarcomas.

The response to Rous sarcoma virus-induced tumors was measured over a 2-yr period using Line UNH 105 New Hampshire chickens segregating for three major histocompatibility (B) complex haplotypes, B22, B26, and B30. Twelve sires and 49 dams were used to produce 489 pedigreed progeny consisting of six B genotypes B22/B22, B22/B26, B22/B30, B26/B26, B26/B30, and B30/B30. Six-wk-old chicks were inoculated in the wingweb with a pseudotype of Bryan high-titer Rous sarcoma virus designated as BH RSV (RAV-1). Resultant tumors were scored six times during a 10-wk period, which served as a basis for a tumor profile index (TPI) assigned to each chick. The B22/B26 chickens (means TPI = 2.6) had the greatest antitumor response, which was significantly different from that of B26/B26 (means TPI = 3.0) and B30/B30 chickens (means TPI = 3.4), the lowest responders. Lower mean TPI of two heterozygotes, B22/B26 (2.6) and B26/B30 (2.9), compared with those of appropriate homozygotes, suggested complementation between B22 and B26 as well as B26 and B30. Chi-square analysis revealed an additional beneficial effect of the B22 haplotype in tumor-bearing chickens, as B22-containing genotypes had a significantly higher survival rate than genotypes not containing B22.

Allelic frequencies in eight alloantigen systems of chickens selected for high and low antibody response to sheep red blood cells.

Parents and offspring from lines of chickens selected for high (HA) and low (LA) antibody response to sheep red blood cell antigen(s) were blood typed for systems A, B, C, D, E, H, I, and L. All birds were homozygous for allele L2, and allelic frequencies for the I system were essentially identical in both lines. In contrast, allelic frequencies of the other blood group systems differed rather markedly between the HA and LA lines.

A study of linkage relationships of blood group P with naked neck, silkie feathering, and recessive white in chicken.

Linkage relationships of blood group P (Ea-P), naked neck (Na), silkie feathering (h), and recessive white plumage (c) were studied to attempt to clarify the h-Na-Ea-P region of linkage group III of the chicken. The Na-Ea-P linkage values obtained in this test agreed with previous reports, and pooled data were used to recalculate a map distance of 27.9 +/- 2.3 map units between these two loci. A significant chi square for linkage was calculated between Na and c; however, because of the relatively low numbers of progeny tested, the high linkage value calculated, and the absence of detectable linkage between c and the other marker genes, this was probably a chance deviation. All other linkage relationships appeared negative, supporting the current suggested linear order of these loci as h-Na-Ea-P with c not being in this chromosomal region.

Metastasis of Rous sarcoma tumors in chickens is influenced by the major histocompatibility (B) complex and sex.

Six-week-old second generation progeny from the cross of inbred Lines 6(1) and 15(1), segregating into three major histocompatibility (B) complex groups (B2/B2, B2/B5, and B5/B5), were inoculated subcutaneously in the wingweb with one of three pseudotypes of Rous sarcoma virus. Chickens that died during a 10-week period after inoculation were necropsied and scrutinized for gross metastasis and histological sections of at least one lesion per affected organ examined for Rous sarcoma-transformed cells. By definition, a metastatic tumor was one located in an organ or tissue other than the primary inoculation site and having the histological appearance of a Rous sarcoma. Sarcomas developed in 1144 chickens, 390 of which died with tumor. For B2/B2, compared to B5/B5 hosts, mortality was 8 vs. 93%, median days to death were 45 vs. 31, and metastatic frequency was significantly lower, 32 vs. 58%. Disseminated lesions were significantly less frequent in females than males and grew preferentially in the heart and pericardial sac. Because the frequency of metastasis was significantly lower in B2/B2 than in B5/B5 chickens, a gene(s) within, or closely linked to, the B complex sharply retards the spread of Rous sarcoma virus-induced tumors.

Chromosomal localization of the major histocompatibility (B) complex (MHC) and its expression in chickens aneuploid for the major histocompatibility complex/ribosomal deoxyribonucleic acid microchromosome.

By the cytogenetic method of trisomy mapping, the major histocompatibility complex (MHC) (B) was located on the microchromosome that also contains all of the ribosomal ribonucleic acid (rDNA) genes that are detected as a nucleolar organizer region. Crosses involving aneuploid chickens homozygous or heterozygous for particular B haplotypes yield an F1 of disomic, trisomic, and tetrasomic offspring suitable for studies of gene dosage effects and gene regulation. Studies to date show that MHC genes are expressed on each chromosome in aneuploid cells unlike the rDNA gene cluster, which is regulated to produce only diploid levels of mature rRNA. Biological effects of extra MHC chromosome dosage range from altered cell surface content of glycoproteins to altered growth potential of chickens. In addition, enhanced MHC-encoded cell surface products may influence the progression of B-cell differentiation and cell population dynamics in the developing bursa of Fabricius. Recent research shows a possible mechanism to account for the formation of unequal products in meiosis within the rDNA and MHC gene clusters. Unequal recombinational events may be promoted in the meiotic process in trisomic chickens.

Selection for body weight at eight weeks of age. 20. Production traits and the B and C alloantigen systems.

The current study evaluated influence of genotypes of the B and C alloantigen systems on production traits in lines of White Plymouth Rock chickens. Lines had been selected previously for high (HWS) or low (LWS) 8-wk BW and after 27 generations of selection, a random sample of each selected line was used to initiate subpopulations in which selection was relaxed. For the present study, blood typing was used to identify allelic frequencies for the B and C systems for five consecutive generations of selection (Generations 30 through 34) and three consecutive generations of relaxation (Generations 5 through 7). Haplotypes for the B complex were assigned designations B32, B33, B34, and B35 and alleles of the C system were assigned C8, C9, C10, and C11. Production traits for males were BW at 4 and 8 wk of age, and for females were BW at 4, 8, and 38 wk of age, age and BW at production of first egg, percentage of normal eggs, and percentage of normal hen-day egg production. There were no differences in production traits among B genotypes or among C genotypes, although some time trends in gene frequencies suggested that more subtle effects may be present.

Response of six major histocompatibility (B) complex recombinant haplotypes to Rous sarcomas.

Six B complex recombinants, BR1 (F24-G23), BR2 (F2-G23), BR3 (F2-G23), BR4 (F2-G23), BR5 (F21-G19), and BR6 (F21-G23), from the fourth backcross generation to highly inbred line UCD 003 (B17B17) were studied for their response to Rous sarcomas. Eight hatches were produced from heterozygous (BRnB17) parents. Chicks were wingweb inoculated with 50 pock-forming units of Rous sarcoma virus (RSV) at 6 wk of age. A tumor profile index (TPI), based on degree of tumor regression, was evaluated by analysis of variance. BR2, BR3, and BR4 are serologically similar F2-G23 recombinants. Haplotype B2, the origin of BF2, is a known tumor regressor, yet BR2BR2 chickens had a significantly lower TPI than BR3BR3 and BR4BR4 chickens. The TPI of BR2BR2 (F2-G23) chickens was also significantly lower than the TPI of chickens homozygous for BR1 (F24-G23) and BR5 (F21-G19). The BR6BR6 (F21-G23) chickens had significantly lower TPI than all homozygotes except BR2BR2 (F2-G23). Among heterozygous genotypes, BR2B17, BR5B17, and BR6B17 differed significantly from BR1B17, BR3B17, and BR4B17. These results suggest that serologically similar recombinants that contain (F2-G23) possess different genes affecting tumor regression. In addition, degrees of tumor regression in BR5 (F21-G19) and BR6 (F21-G23), both of which contain BF21, may be due to genetic differences within the B-F/B-L or B-G regions.

Immunoresponsiveness in chickens: association of antibody production and the B system of the major histocompatibility complex.

Lines of White Leghorn chickens were selected for high or low antibody response to sheep erythrocytes for five generations. The base population from which the experiment started was composed of individuals all of which were heterozygous at the MHC haplotypes B13 and B21. Body weights, egg production traits, and genotypes at the B system were monitored for all individuals in each generation. By Generations 4 and 5 there was separation of the two replicate lines selected for high titer from the two replicate lines selected for low titer. Over the course of the experiment, higher antibody titers and lower BW were associated with B21 and lower antibody titers and higher BW were associated with B13, although these relationships did not occur in every instance. Conclusions were that the B system was associated with antibody response, but that the chickens did not depend entirely upon that association for protection against foreign proteins. Also, the importance of having replicate lines in a selection experiment was shown.

Production traits and alloantigen systems in lines of chickens selected for high or low antibody responses to sheep erythrocytes.

The selection of chickens for high (HA) and for low (LA) antibody titers to sheep erythrocytes has produced differences in the selected trait and in the correlated responses in body weight, egg production, and erythrocyte antigens. The response to selection continued through 14 generations. There was considerable divergence between lines for erythrocyte alloantigen systems, including the major histocompatibility complex. Females from Line LA were heavier as juveniles and lighter as adults, matured at a younger age, and had higher egg production than those from Line HA. There were no differences between lines for the incidence of defective eggs laid-except for the percentage of eggs with double-yolks, which was greater for Line LA than HA. The phenotypic correlations of antibody response with growth and with reproductive traits were very low; the genetic correlations were moderate to high for most of these traits.

Neurotoxicity of triorthotolyl phosphate in chickens of different genotypes in the presence and absence of deoxycorticosterone.

Indices of acute and delayed toxicity following administration of triorthotolyl phosphate (TOTP) were measured in roosters from lines of chickens originating from the Cornell randombred population. Matings were designed to produce individuals that had presence or absence of allele 21 of the B blood system. Non-B21 individuals had allele 13 or 31. Acute inhibition of esterases (neurotoxic esterase, liver cholinesterase, plasma cholinesterases, and plasma carboxylesterases) occurred in all birds within 24 hr of a single oral dose of 360 mg/kg TOTP. Clinical signs of delayed neuropathy were evident within 12 days of TOTP administration, with no significant difference between genotypes. Dietary deoxycorticosterone (40 to 200 ppm) appeared incapable of statistically significant modification of the strong effects of TOTP. Activities of blood esterases were different between roosters having B21/B21 and those with B13 and/or B31.

Resistance to natural and controlled exposures to Eimeria tenella: genetic variation and alloantigen systems.

Chickens from lines selected for high (HA) and low (LA) antibody response to sheep erythrocyte antigens were used to study relationships between blood group systems and resistance to Eimeria tenella. Results of natural and controlled exposures to E. tenella showed Line HA chickens to be more resistant than those from Line LA. Differences in resistance to E. tenella were found among alleles for the I blood group system with degree of resistance depending on the background genome.

Monoclonal antibody differentiates chicken A system alloantigens.

A monoclonal antibody (ISU-cA) was produced that recognized certain alloantigens of the chicken A blood group locus. Antigens produced by alleles A3, A4 and A8 were positive, and those produced by A2 and A5 were negative, by haemagglutination. The specificity of ISU-cA for chicken A blood group antigens was demonstrated by serologic analyses, genetic crosses and competitive inhibition of binding by anti-A alloantisera. To our knowledge, this is the first reported monoclonal antibody against a chicken blood group alloantigen system other than the B complex.

Marek's disease and major histocompatibility complex haplotypes in chickens selected for high or low antibody response.

Sublines of chickens differing in genotypes at the major histocompatibility complex (MHC) were developed from lines selected for high (HA) and low (LA) antibody response to sheep erythrocytes. To evaluate the influence of MHC genotypes in diverse background genomes on resistance to Marek's disease, chicks with MHC genotypes B13B13, B13B21 and B21B21 from both background genomes were exposed naturally commencing at 1 day of age. Individuals which died up to 120 days of age were autopsied to determine cause of death. Mortality due to Marek's disease was greater for HA than LA chickens and greater for males than females. Interactions of MHC genotypes with background genome and with sex suggest a complex picture of the influence of MHC genotypes. A heterozygous advantage for resistance to Marek's disease was noted, as would be predicted by genetic theory concerning maintenance of polymorphism at the MHC.