Antibody titers and plasma glucocorticoid concentrations near weaning in steer and heifer calves.

Abstract

The involvement of adrenal glucocorticoids and immunologic competence has been under investigation in laboratory animals for many years. As early as 1936, Selye (16) reported that injury to rats or stressful stimuli could cause adrenal enlargement and thymic involution. More recent experimentation demonstrated that glucocorticoids are involved with depletion of cortical thymic lymphocytes and with depressions in germinal centre formation and lymphoid cell proliferation in the spleen of mice (4, 9, 14). In mice, the period of maximum sensitivity to glucocorticoid action on loss of spleenic mass and reduction of antibody production was between 24 and six hr prior to sheep red blood cell (SRBC) injection (8). Studies in which laboratory mice are subjected to crowding reveal that this stress leads to reduced antibody production following injections of SRBC and a decreased capability of the laboratory animals to resist parasitic invasion (2, 3). Although the literature abounds with data on the effects of stress on antibody production in laboratory animals (2, 3, 4, 8, 9, 12, 16), there is a relative paucity of information delineating stress involvement with humoral or cell mediated immunity in domestic animals. Research with chickens has demonstrated that stress and elevated blood glucocorticoid concentrations are involved with both humoral and cell mediated immunity (5, 6, 15, 19, 20). Thaxton et al (19) found no decline in antibody titers to SRBC when chickens were exposed to heat stress. However, adrenocorticotropin (ACTH) injections between 24 and nine hr prior to antigen injection reduced antibody titers. The objective of this study was to evaluate relationships of antibody production to porcine red blood cells (PRBC), equine red blood cells (HRBC) and plasma glucocorticoid concentrations near the stressful time of weaning in beef calves.