EFF~.CT OF IN VITRO EXPOSDRE OF CELLS TO ANTmEN UPON LEUKOCYTIC TRANSFER OF DELAYED HYPERSENSITIVITY* BY FRED S. KANTOR,~ M.D

The mechanism of delayed hypersensitivity is poorly understood due in large part to limited techniques for in vitro study. With the exception of the human species, live leukocytes obtained from peripheral blood, lymph nodes, spleen, or peritoneal washings have been required to transfer delayed hypersensitivity from a sensitized donor to a normal recipient (1). Study of direct interaction between sensitized donor cells and antigen, in the recipient's skin, is hampered by the finding that most of the leukocytes at the site of a delayed reaction are from the recipient and not the donor (2). The present studies were designed to investigate the interaction of donor cells and antigens in vitro, and to study the effect of antigen exposure upon the ability of sensitized donor cells to transfer delayed sensitivity. The results indicate that exposure to certain antigens reduced or ablated the transfer of delayed hypersensitivity, and that this interference was related to the degree to which antigens remained associated with cells after exposure in vitro. Evidence is presented that size of the antigen was more important than either degree of conjugation, or charge, in determining cell association of antigens.