Immunodepression in Young Chickens by High Environmental Temperature

INTRODUCTION EXPOSURE to high environmental temperature before a primary antigenic challenge causes inhibition of the development of the primary immune response in young chickens (Thaxton et al., 1968). Although adrenocorticotropin (ACTH) and corticosteroids depress the normal immune response in mammals (Elliott and Sinclair, 1968) and birds (Glick, 1967), indicators of the stress response, such as adrenal cholesterol depletion or changes in circulating leucocytes, were not observed in the heated birds (Thaxton et al., 1968). The present objective was to determine whether already established primary antibody titers could be reduced by high environmental temperatures. METHODS Immunizations of Athens Randombred males were conducted according to the schedule given in Table 1. Circulating antibody titers were measured using the plate hemagglutination technique, the qualitative precipitation technique, and the standard tube agglutination test, respectively, for the three antigen systems which were: 1) sheep-red blood cells (SRBC), 2) bovine serum albumin (BSA), and 3) Salmonella…