Interaction of high temperature and Salmonella pullorum antigen concentration on serum agglutinin and corticosteroid responses in white rock chickens.

In three experiments, 6- to 7-week-old chickens were exposed to one or two standard heating episodes and were injected immediately afterward with different concentrations of heat-killed Salmonella pullorum antigen (Ag) or phosphate-buffered saline. The standard heat episode consisted of three .5-hr exposures of 44 to 46 C with .5-hr periods of 22 C between exposures. Nonheated chickens were maintained at 22 C. When two heating episodes were used, there was a 12-hr interval between episodes. Sera from blood collected at 0 through 15 days postimmunization (PI) were titrated for total agglutinins and assayed for corticosteroids in all three experiments. Additionally, in Experiment 3, sera were titrated for 2-mercaptoethanol-resistant (2-MER) antibody. Total agglutinins were suppressed from 5 through 13 days PI by one heating episode in birds receiving lower doses of Ag but not in those receiving higher doses. When birds were exposed to two heat episodes, 12 hr apart, total agglutinin titers were suppressed in birds receiving the low Ag dose during the induction phase (4 to 5 days PI) only. During the declining phase (7 to 14 days PI), the effect was reversed, and titers were significantly lower in heated birds receiving the higher dosage. These results are similar to those previously obtained with ACTH (adrenocorticotropin). Determination of 2-MER antibody indicated that IgM was probably suppressed during the induction of the immune response but that IgG was suppressed during the declining phase of the response. Serum corticosteroid concentrations were significantly increased immediately after exposure to high temperature.(ABSTRACT TRUNCATED AT 250 WORDS)