Studies on the Human T-Lymphocyte Population

Abstract

Abstract The IgG fraction of a goat antibody prepared against human infant thymus cells and extensively absorbed with pooled human red blood cells, insolubilized human Ig and cells from a patient with chronic lymphocytic leukemia (ATG), was used to study human peripheral lymphocyte populations. ATG inhibited the response of human peripheral lymphocytes to concanavalin A (Con A) but not to pokeweed mitogen (PWM). The F(ab′)2 and Fab′ fragments of ATG were as effective as ATG in inhibiting Con A induced 3H-thymidine incorporation. ATG did not interact with Con A or the receptor for Con A on the lymphocyte but was inhibitory in the absence of complement as a result of its apparent selective cytotoxicity. The antibody also inhibited 3H-thymidine incorporation in the one-way mixed lymphocyte reaction, again without affecting the response of these cells to PWM. The specificity of ATG for the T-lymphocyte population was also suggested by fluorescent labeling experiments which indicated that ATG reacted with only 50 to 80% of human peripheral lymphocytes. These results suggest that ATG is directed toward antigens unique to the human T-lymphocyte population. Moreover, it appears that ATG can be used to study human T-lymphocyte responses and to follow the isolation of T-specific antigens.