In Vitro Studies of Cellular Hypersensitivity

Some characteristics of inhibition of cell migration induced in tissue culture by the addition of specific antigen were studied. The following characteristics were found to be shared by this type of cellular hypersensitivity and delayed cutaneous sensitivity: 1. Specificity for the carrier moiety of haptene protein conjugates. The picryl protein conjugate used to sensitize guinea pigs inhibited migration of monocytic cells from these animals. Other picrylated proteins produced little inhibition. 2. Enhancement by mycobacterial adjuvants. Incorporation of tubercle bacilli with picrylated proteins in adjuvant-antigen emulsions stimulated the development of this cellular hypersensitivity to antigen. 3. Independence of circulating antibody. In contrast to cellular hypersensitivity, serum antibody (a) reacted with any of a number of picrylated proteins, (b) developed well in the absence of mycobacterial adjuvant, and (c) persisted in unchanged titer for 5 weeks in animals sensitized with saline solutions of antigen. During this time cellular hypersensitivity decreased remarkably. The in vitro system described provides a direct method to measure cell-antigen interaction and permits study of an aspect of the immune response not mediated by humoral antibody. The relation of cellular hypersensitivity to antibody formation and delayed hypersensitivity is discussed.