Absence of Influence on Immune Competence by the Sex-Linked Gene (K) Determining Slow Feathering in White Leghorn Chickens

Males of white leghorn strain crosses heterozygous (Kk) for the sex-linked feathering locus genes were mated to rapid-feathering (k-) females to produce rapid- and slow-feathering chicks of both sexes. K did not influence humoral-mediated immunity against challenge with sheep erythrocytes, killed Brucella abortus, or killed infectious bursal disease virus. Chicks challenged at 3 weeks of age had higher primary responses and higher titers of 2-mercaptoethanol-resistant antibody (IgG) than those challenged at 1 week of age. K had no influence on levels of cell-mediated immunity based on responses in in vitro phytohemagglutinin tests of donors 2 to 126 days of age, on responses in in vitro one-way mixed-lymphocyte cultures, and on rejection rates of skin grafts on young chicks. Feathering type did not influence viremia or antibody to avian leukosis virus; the level of lymphoid leukosis tumors was higher in rapid-feathering females than in slow-feathering females at 28 weeks of age (53% vs. 72%; P less than or equal to 0.10). We conclude that K does not influence general immune competence. The possibility that it may influence specific immunity to ALV under conditions not met in this study, because of an endogenous virus recently associated with the K locus, is discussed.