The effects of extracorporeal whole body hyperthermia on the functional and phenotypic features of canine peripheral blood mononuclear cells (PBMC)

In this study the effect of transient 42.3 degrees C whole body hyperthermia (WBH) on the distribution of PBMC phenotypes and in vitro blastogenic responsiveness was determined in dogs. Hyperthermia (n = 6) was induced by heating venous blood during extracorporeal circulation (venous perfusion WBH); perfused non-heated dogs (n = 4) were used as controls. Both euthermic and hyperthermic perfusion produced transient lymphopenia which normalized in controls after perfusion but persisted in hyperthermic animals throughout the 8-day post-perfusion observation interval. The transient lymphopenia in control dogs was non-selective. In contrast, WBH-associated lymphopenia was selective, in that CD5(+) T lymphocytes were more sensitive to hyperthermia than sIg(+) B cells and, within the T cell compartment, suppressor (CD8(+)) cells were more sensitive to hyperthermic stress than helper (CD4(+)) lymphocytes. Functional analyses showed that WBH caused persistent suppression of PBMC blastogenesis in response to T cell phytomitogens. Increased plasma cortisol levels were correlated to peak lymphopenia and hyporesponsiveness to phytomitogens. Despite these alterations, high grade WBH was well tolerated and there was no evidence of opportunistic infection.