title: Immunoregulatory effects of fraction 5 thymus peptides. I. Thymosin alpha 1 enhances while thymosin beta 4 suppresses the human autologous and allogeneic mixed lymphocyte reaction.
abstract: Thymosin alpha 1 and thymosin beta 4, two peptides isolated from preparations of calf thymus fraction 5, were tested in the human mixed lymphocyte reaction (MLR). Thymosin alpha 1 was found capable of enhancing both the allogeneic and autologous MLR. On the contrary, thymosin beta 4 suppressed MLR proliferative responses. Study of the responses of the T cell subpopulations revealed that T4+ (helper/inducer) cells but not T8+ (suppressor/cytotoxic) are responsible for the enhanced, proliferative response to allo- and autoantigens in the presence of thymosin alpha 1. Both the autologous and the allogeneic proliferative responses of either T4+ cells or T8+ cells were not influenced by the addition of thymosin beta 4 in the cultures. However, when T4+ and T8+ subsets were cocultured, thymosin beta 4 was capable of activating T8+ cells to suppress the allogeneic and the autologous proliferative response of T4+ cells. These studies show that thymosin fraction 5 peptides exert immunoregulatory effects on the human MLR proliferative responses in vitro.
mesh_terms: D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation / Q000187:drug effects; D007959:Lymphocyte Culture Test, Mixed; D009000:Monocytes / Q000187:drug effects / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D000077596:Thymalfasin; D013947:Thymosin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000099201:Thymosin beta(4)
chemical_list: D000077596:Thymalfasin; D013947:Thymosin; D000099201:Thymosin beta(4)