Unrelated delayed hypersensitivity reactions accelerate the recovery of immunological responsiveness of specifically depleted cell populations.

Normal CBA mouse spleen cells were specifically depleted of cells spontaneously reacting to pigeon erythrocytes (PRBC) by two methods, the first allows specific depletion of anti-PRBC thymus derived (T) rosette forming cells (RFC) whereas the second depletes bone marrow derived (B) anti-PRBC hemolytic plaque forming cells (PFC). Depleted populations transferred into lethally irradiated syngeneic recipients and stimulated with PRBC failed to develop any significant response but they normally responded to a stimulation with sheep erythrocytes (SRBC). When spleen cells were taken from mice skin painted with picryl (trinitrophenyl: TNP) chloride 12 days before and the recipients were challenged in the same way and stimulated with PRBC, they become capable of producing a definite response to this antigen. Moreover in these animals, a consistent although low number of cells was found, which simultaneously reacted to both native PRBC and TNP conjugated SRBC. These findings show that unrelated delayed hypersensitivity reactions promote the immunological recovery of specifically depleted cell populations.