title: Antigen reactive memory T cells are defined by Ta1.
abstract: Ta1 is a 105,000 dalton protein that is weakly expressed on a small fraction of resting human peripheral blood T cells but strongly expressed in vitro on T cell clones and a substantial proportion of activated T cells. Unlike receptors for growth factors such as IL 2, the Ta1 antigen is present on T cell lines and clones irrespective of cell cycle. The function of Ta1 was investigated after separation of T lymphocytes into Ta1-enriched and Ta1-depleted subpopulations that were obtained from normal human subjects. Although Ta1-enriched T cells constitute only 10 to 15% of the E rosette-positive lymphocyte population, most, if not all, of the anamnestic response to the recall antigens tetanus toxoid and mumps reside in the Ta1+ population. Both Ta1-enriched and -depleted cells responded equally well to the mitogen PHA. The autologous mixed lymphocyte response was also greater in the Ta1-enriched subpopulation but not to the degree seen with soluble antigen. Increased proliferation was not due simple to increased inducer cell function within the Ta1+ subpopulations because both Ta1- and Ta1+ cells induced similar amounts of Ig synthesis in the presence of PWM. Additionally, increasing numbers of Ta1- cells did not suppress the enhanced proliferative responses of Ta1+ cells, and thus Ta1- cells do not appear to be functioning as suppressor cells. The Ta1 antigen appears to be a marker for previously activated T cells in peripheral blood, and this subpopulation appears to include T memory cells.
mesh_terms: D000954:Antigens, Surface / Q000276:immunology*; D002469:Cell Separation; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis; D007156:Immunologic Memory; D007700:Kinetics; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D009109:Mumps virus / Q000276:immunology; D011043:Pokeweed Mitogens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*; D013745:Tetanus Toxoid / Q000276:immunology; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
chemical_list: D000954:Antigens, Surface; D007136:Immunoglobulins; D011043:Pokeweed Mitogens; D013745:Tetanus Toxoid; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7