INESCAPABLE FOOTSHOCK EXPOSURE DIFFERENTIALLY ALTERS ANTIGEN-STIMULATED AND MITOGEN-STIMULATED SPLEEN-CELL PROLIFERATION IN RATS

A variety of stressors have been shown to influence specific and non-specific measures of immune function in laboratory animals. One of the most common tools used to evaluate lymphocyte function is the non-specific mitogen proliferation assay. Assessment of this function in the rat spleen has revealed profound suppression following restraint, electric shock, and re-exposure of animals to a fearful context. However, there have been no studies that have compared the effects of stressor exposure on mitogen- and specific antigen-stimulated spleen cell proliferation. Therefore, the present study addressed this issue through experiments in which rats were immunized intraperitoneally with 1 mug cholera toxin and exposed to acute (one session) or repeated (three consecutive daily sessions) footshock. The results showed that footshock exposure prior to immunization inhibited cholera toxin stimulated spleen cell proliferation 7 days after immunization. Acute or repeated footshock exposure 5-7 days after cholera toxin immunization depressed non-specific spleen cell proliferation, while augmenting the proliferative response to specific antigen. From these observations it can be hypothesized that footshock exposure either differentially regulates lymphocyte activation by clonal and polyclonal signals, and/or naive and memory cells react differently to stressor exposure.