Major histocompatibility (B) complex-associated differences in the delayed wattle reaction to staphylococcal antigen.

The influence of the major histocompatibility (B) complex on the delayed wattle reaction (DWR) to Staphylococcus aureus was studied in 109 segregants (B2/B2, B2/B5, and B5/B5) of a fourth generation cross between inbred Regional Poultry Research Laboratory lines 6(1) and 15(1). Chickens were sensitized at 6 weeks of age with S. aureus antigen. One week later, DWR was evaluated by injecting the right wattle with S. aureus antigen. Thickness measurements were taken 4, 24, 48, 72, and 96 hr after injection. A quadratic equation model was used for each bird to calculate maximum wattle thickness, hour of maximum response, and rate of response development and decline. In males, the maximum wattle thickness in response to S. aureus antigen was significantly greater in B2/B5 heterozygotes (1.77 +/- .07 mm) than in either homozygote, B2/B2 (1.36 +/- .13 mm) or B5/B5 (1.39 +/- .08 mm). Heterozygous males reached maximum response sooner and recovered more quickly than homozygous males but these differences were not statistically significant. In females, response developed later than in males but no B complex effect was detected in either rate of development or maximum response.