A new immunomodulator, LF 1695--I. In vitro effects on the T lymphocyte lineage in man.

A new immunomodulator, LF 1695, was analyzed in vitro for its capacity to induce T cell markers (HTLA and OKT3, 4 and 8 antigens), to enhance the mitogen-induced lymphocyte proliferation, and to increase the Con A-induced suppressor activity. The inductive activity was compared with that of thymic hormone (thymosin fraction V). LF 1695 was capable of significantly augmenting the percentages of HTLA+ cells (10-15%) and of OKT 3+,T4+, or T8+ cells (13-28%) in human bone marrow prothymocytes. Maximum induction was observed at the concentration of 0.5 microgram/ml. In addition, LF 1695 significantly augmented the proliferation of human peripheral blood lymphocytes stimulated by mitogens (Concanavalin A, phytohemagglutinin, pokeweed mitogen and phorbol myristate acetate). LF 1695 also increased the Con A-induced suppressor activity of human lymphocytes. These data indicate that LF 1695 is active both on T cell precursors and on more mature T cells.