In vitro detection of spontaneously occurring delayed-type iso-hypersensitivity.

The delayed-type iso-hypersensitivity that guinea-pigs acquire spontaneously towards a β-globulin antigen of other guinea-pigs has been measured in vitro. Serum containing the antigen specifically triggers lymphocytes from naturally iso-hypersensitive animals to undergo blastogenic response. This reaction is similar to that of lymphocytes cultured in the presence of antigen to which cell donors have been intentionally immunized. Thus, the in vitro technique of DNA synthesis may be used to detect both artificially induced and naturally occurring delayed-type hypersensitivities. In addition, naturally existing delayed hypersensitivity offers a plausible explanation for reports of spontaneous transformation of lymphocytes by homologous or heterologous serum and of certain other in vitro phenomena involving interaction of lymphoid cells from non-immunized donors.