Effects of chronic heat and cold stressors on plasma immunoglobulin and mitogen-induced blastogenesis in calves.
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 degrees C), constant cold (-5 degrees C), or thermoneutral (23 degrees C) ambient conditions in environmentally-controlled 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 G1 or M. These data demonstrate that chronic heat and cold stressors affect calves by altering both antibody- and cell-mediated immunity.
D000818:Animals; D002417:Cattle / Q000276:immunology*; D003080:Cold Temperature; D003208:Concanavalin A; D006358:Hot Temperature; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D007136:Immunoglobulins / Q000032:analysis*; D008213:Lymphocyte Activation; D008297:Male; D008934:Mitogens; D010835:Phytohemagglutinins; D013312:Stress, Physiological / Q000276:immunology / Q000662:veterinary*
D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007136:Immunoglobulins; D008934:Mitogens; D010835:Phytohemagglutinins; D003208:Concanavalin A