Effects of Chronic Heat and Cold Stressors on Plasma Immunoglobulin and Mitogen-Induced Blastogenesis in Calves

Abstract

Fifty-six Holstein calves were used to investigate effects of heat and cold stressors on mitogen-induced blastogenesis of isolated peripheral blood mononuclear cells and immunoglobulins G1 and M in blood plasma. Calves were exposed to constant hot (35° C), constant cold (—5°C), or thermoneutral (23°C) ambient conditions in environmentallycontrolled chambers. Immune responses were measured soon after introduction into environmental chambers (3 days) and after various degrees of adaptation (7 and 14 days). Mortality was greater among heat- and cold-exposed calves than among thermoneutral calves. Neither heat nor cold exposure had a direct effect on blastogenesis of peripheral blood mononuclear cells by phytohemagglutinin or concanavalin A. Plasma from heat- and cold-exposed calves then was incorporated into the culture medium at a final concentration of 5% and tested in a mitogenesis assay on peripheral blood mononuclear cells from a single healthy donor. Plasma from heat-exposed calves consistently enhanced tritiated thymidine incorporation into normal peripheral blood mononuclear cells by phytohemagglutinin and concanavalin A as compared to plasma from cold-exposed calves. After heat exposure for 3 to 14 days, immunoglobulin G1 averaged 27% less in heat-exposed calves than in calves that were held at thermoneutrality, but M was unaffected. Cold exposure did not have a consistent effect on G: or M. These data demonstrate that chronic heat and cold stressors affect calves by altering both antibody-and cell-mediated immunity. © 1982, American Dairy Science Association. All rights reserved.