EFFECTS OF MAJOR HISTOCOMPATIBILITY COMPLEX ON ANTIBODY-RESPONSE IN F1 AND F2 CROSSES OF CHICKEN LINES

Lines of chickens selected for 9 generations for high (H) and low (L) antibody (Ab) response to sheep red blood cells (SRBC) were crossed to produce F1 (n = 761) and F2(n = 1033) populations. All animals were t yped for major histocompatibility complex (MHC) B-types. Effects of MH C genotypes and haplotypes on the Ab titer to SRBC were estimated. The MHC genotypes and remaining genotype explained 2.5% and 31% of the to tal variation of the Ab titer in the F2 respectively. Estimates of MHC effects in the F2 were similar to estimates in the selected lines. Th e 119 and 121 B-haplotypes were associated with a significantly higher response than the 114 and 124 B-haplotypes. These results confirm the hypothesis that changes in B-type distribution observed in the select ed lines could be related to a direct or closely linked effect of MHC on the immune response.