A human lymphocyte chemotactic factor produced by the mixed lymphocyte reaction

Lymphocytes migrate to and concentrate at sites of antigenic challenge. Although these cells are seen in delayed cutaneous hypersensitivity reactions and graft rejections, the mechanism by which they are attracted to these sites is poorly understood. In the current study, human mononuclear cells from normal subjects were cultured for 7 days in a standard two-way MLR. Supernatants from the MLR were assayed at various times for the presence of lymphocyte chemotactic activity. Results indicate that a lymphocyte chemotactic factor is produced by the MLR, with maximal activity appearing after 24 to 48 hr of culture. This activity is diminished with longer incubation times. The observed factor is heat labile after a 56° C, 30 min heat treatment and preferentially attracts T lymphocytes. Additional studies demonstrate that MLR supernatants stimulate both directional locomotion (chemotaxis) and enhanced random locomotion (chemokinesis) in T cells. The release of such a human T lymphocyte chemotactic factor during the MLR may represent an important mechanism of attracting lymphocytes to a site of antigenic challenge.