Evidence is presented for a crossover between the genes coding for the serologically determined (SD) antigens on erythrocytes and an immune response gene (Ir-GAT) controlling immune response to the synthetic polypeptide GAT within theB complex, the MHC of chickens. TheIr-GAT (1) andIr-GAT (19) alleles control low and high immune response to GAT, respectively. Both low and high responders were recovered as recombinants fromB (1) B (1) andB (19) B (19) birds. The low-responder haplotypes are homozygous for theIr-GAT (1) allele and the high-responder haplotypes carry theIr-GAT (19) allele. Mortality forB (1) B (1) nonresponder birds was 39%, compared with 19% for theB (1) B (1) high responders; this suggests the possibility that genes located within the immune response region of theB complex exert some genetic control over viability and survival.

Sequential probability tests were employed to examine genetic linkage among, cattle A, B, C, F, J, L, M, S, Z, and R' blood group loci, the hemoglobin locus, the serum transferrin, amylase, and alkaline phosphatase loci, and the milk protein loci beta-lactoglobulin, alpha S1-casein, beta-casein, and kappa-casein. Linkage was evident between the A and hemoglobin loci, the J and beta-lactoglobulin loci, the alpha S1-casein and beta-casein loci, the alpha S1-casein and kappa-casein loci, and the beta-casein and kappa-casein loci. Recombination fractions for these respective combinations were 0, .18, .03, .04, and .06. There was a suggestion of possible loose linkage (recombination fraction = .4) between the beta-lactoglobulin locus and the casein complex. Linkage could be excluded for most other combinations at .25 recombination.

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Summary Immune response to poly‐(l‐tyrosine‐l‐glutamic acid)‐poly‐d, l‐alanine‐poly‐l‐lysine ((T,G)‐A–L), human serum albumin (HSA), and (l‐glutamic acid50, l‐tyrosine50)n (GT) was found to be linked to the B complex in an outbred line of Leghorns segregating for the B1, B2, and B19 alleles. Birds of the blood group genotypes B1B1, B2B2, and B19B19 were low, intermediate, and high responders, respectively to either (T,G)‐A–L or HSA. Response to GT, however, differed, with the B2B2 genotype being the only responder. No real genotype differences in immune response to DNP‐conjugates and sheep red blood cells (SRBC) could be detected.

SummaryBovine erythrocyte treatment with chymotrypsin, trypsin, pronase, papain, or ficin eliminated or weakened the reactivity of 18 of the 47 blood group factors which were examined. Thirteen of the affected factors were from the B system, and one each was from the C, FV, L, M, and R'S' systems. Variation attributable to pheno‐group (allele) or genotype influences was observed in the effects upon six of the factors. Ficin‐treated V/V, but not F/V or F/F, cells were rapidly lysed by normal rabbit serum (complement control). Absorptions with pronase‐treated V positive cells indicated that essentially all V antigenicity was removed. However, immunizations with pronase‐treated V positive cells elicited V antibody production in one of two recipient cows. The numbers of antigens removed by different enzymes did not appear to be closely related to the amount of protein removed.