Surgery, trauma and immune suppression. Evolving the mechanism.

A major surgical procedure can impair the delayed hypersensitivity response. This impairment is associated with suppressor cell activity that can alter either afferent or efferent responses. Using the third party mixed leukocyte culture to define cell types involved, major immune impairment was seen with the combination of both nonadherent and plastic adherent cells, suggesting that a T cell-macrophage interaction is required. A serum factor(s) is present in operated mice that can impair mixed leukocyte culture reactivity. A serum factor(s) in an adoptive transfer experiment is also capable of enhancing primary tumor growth. A unifying hypothesis, based predominantly on data from the current literature, is presented in an attempt to elucidate the mechanism by which all forms of major trauma are associated in some patients with "paradoxical" immune suppression.