Resting and sensitized T lymphocytes exhibit distinct stimulatory (antigen-presenting cell) requirements for growth and lymphokine release.
Previous studies have shown that unprimed or resting T lymphocytes will grow and release lymphokines when stimulated by dendritic cells (DC). We now have examined the stimulatory requirements for antigen-primed or blast-transformed T cells. The latter were derived from dendritic/T cell clusters that developed during the primary mixed leukocyte reaction (MLR). The specificity of the blasts was established by a binding assay in which most T cells aggregated small B lymphocytes of the appropriate haplotype within 2 h at 4 or 37 degrees C. Since unprimed T cells did not aggregate allogeneic B cells, we suggest that DC induce T lymphocytes to express additional functioning receptors for antigen. Lyt-2-T blasts did not grow or release interleukin 2 or B cell helper factors unless rechallenged with specific alloantigen, whereupon growth (generation time of 14-18 h) and lymphokine release rapidly resumed. The blasts could be stimulated by allogeneic macrophages, B cells, and B lymphoblasts, whereas the primary MLR was initiated primarily by DC. responsiveness appeared restricted to the I region of the major histocompatibility complex, and varied directly with the level of Ia antigens on the stimulator cells. The interaction of B cells and T blasts was bidirectional. The T blasts would grow and form B cell helper factors, while the B cells grew and secreted antibody. However, the efficacy of T cell-mediated antibody formation was enhanced some 10-fold by the addition of specific antigen. Therefore, responses of resting helper T cells, then, are initiated by antigen plus DC. Once sensitized, T blasts interact independently with antigen presented by other leukocytes.
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002455:Cell Division; D005260:Female; D007518:Isoantibodies / Q000032:analysis; D007959:Lymphocyte Culture Test, Mixed; D008222:Lymphokines / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*
D007518:Isoantibodies; D008222:Lymphokines; C029805:Lyt antibodies