IN VITRO STUDIES ON DELAYED HYPERSENSITIVITY AND HOMOGRAFT IMMUNITY *

Transplantation immunity, and reactions of delayed hypersensitivity appear to have many features in suggesting that the two phenomena are closely related and the tissue damage encountered may indeed be mediated by the same mechanisms. One of the goals underlying our studies on delayed hypersensitivity using conventional antigens and known antibody systems was the logical extension of the studies to other tissue destructive states where delayed hypersensitivity is thought to play a role (e.g., homograft reactions, allergic encephalomyelitis, etc.) . The present paper will describe in vitro studies on delayed hypersensitivity and homograft reactions. The investigation of delayed hypersensitivity in v i m was begun more than 30 years ago and the publications on the subject are abundant, interesting, and often conflicting. Since the literature has been extensively considered and reviewed el~ewhere,3-~ it will not be dealt with here. Studies were undertaken in which the migration of peritoneal exudate cells was observed in the presence of antigen. Evidence will be presented that the migration of cells obtained from guinea pigs exhibiting delayed hypersensitivity to tuberculin, ovalbumin, or diphtheria toxoid is inhibited by specific antigen; however, cells obtained from animals actively engaged in the production of serum antibody are not affected by antigen. Sera taken from animals exhibiting delayed hypersensitivity or sera containing precipitating antibody did not sensitize normal cells. It will also be shown that the migration of peritoneal cells from mice sensitized by skin homografts is inhibited by antigen from the donor of the skin graft.