Effect of Divergent Selection for Immune Responsiveness and of Major Histocompatibility Complex on Resistance to Marek's Disease in Chickens

Abstract

Lines of chickens selected for nine generations for high (H) or low (L) antibody response to SRBC, a randombred control (C) line, and an F1 cross between H and L lines were challenged for resistance to Marek's disease (MD). Hens only were challenged at day-old by contact with virulent MD Strain K. Birds were serologically typed for MHC erythrocyte antigens. Chicks from the L and H lines died earlier and later, respectively, than the C chicks, whereas time of death did not differ between F1 birds and the L chicks. Mortality in the L line (70.1%) was higher than in the C line (42.8%), but mortality in the H line (40.9%) was not lower than in the C line or the F1 cross (47.5%). Effects of MHC genotypes and haplotypes on mortality from MD were estimated within lines with a logistic regression model. Effect of MHC was moderate in the H line (P < .10) and highly significant in the C line (P < .005). Effects of MHC genotypes were similar in the H and C line but differed in the L and F1. Heritability of mortality from MD estimated with a threshold model including relationships between individuals was .40 when all lines were grouped together, whereas heritability estimated for each line separately was .45, .51, and .78 in the H, C, and L lines, respectively. Correlations between estimated breeding values for antibody response to SRBC and mortality from MD varied between lines and sexes. Correlations also were affected by whether or not the MHC effect was taken into account.

A tradeoff between immunocompetence and sexual ornamentation in domestic fowl

“…Although selection focused only on this aspect of immune function, previous studies showed that humoral responsiveness to a variety of antigens (Escherichia coli, Newcastle disease virus, bronchitis virus, bursal disease virus) varied between selection lines in a similar fashion (20). Furthermore, selection lines differed in size of spleen and bursa (35), cellular immunity in vivo (36), and mortality after infection with Marek's disease (37). Thus it seems safe to assume that immunocompetence was successfully manipulated.…”

Immunological basis of differences in disease resistance in the chicken

“…A comprehensive review on the MHC linkage with differences in disease resistance has been given in several papers: resistance to viral infections [18,42,66,88,104,133,137], resistance to bacterial infections [29,46,122], resistance to protozoal infection [21,86,129], and autoimmune diseases [114].…”

“…The HA and LA also show difference in T cell responses; for instance, the HA lines have a high percentage of CD4 + T cells, while the LA lines have more CD8 + T cells in the spleen and thymus [102]. The LA chickens show an enhanced cellular response characterised by T cell proliferation and macrophage activity that could improve their resistance to intracellular bacteria and some viruses such as MDV in which antibodies are of less importance [43,104]. The difference in the other immune parameters such as macrophage activity [71] and in preferential T cell responses and proliferation [43] and perhaps the antibody response itself, might possibly be related to the discrepancy in cytokine responses in HA and LA lines.…”

Differential Antibody Responses in 6.B Major Histocompatibility (B) Complex Congenic Chickens

“…The B 13 haplotype had 98% frequency in the low responder line. In another selection experiment, a high SRBC antibody line had an increased frequency of B 12 l and the low antibody line had an increased frequency of BU4 and B 12 4 (Pinard et al, 1993).…”