Cellular immunity in cosmonauts during long duration spaceflight on board the orbital MIR station.

To investigate the effect of spaceflight on cell mediated immunity we tested delayed-type hypersensitivity (DTH) in 5 cosmonauts on three missions in the orbital space station MIR. DTH was determined by the intradermal application of seven antigens and a control using the standardized Multitest Merieux. This multiple prick puncture test was applied prior to, during, and following missions, which lasted for up to 177 d. In four of the five cosmonauts, reaction scores of DTH-responses below the warning level were noted during flight (two subjects) or following landing (two subjects)