ALA-1 - MURINE ALLOANTIGEN OF ACTIVATED LYMPHOCYTES .2. T AND B EFFECTOR CELLS EXPRESS ALA-1

Abstract

Ala-1 (activated lymphocyte antigen-1) is a murine alloantigen expressed only on activated peripheral T [thymus-derived] and B [bone marrow-derived] lymphocytes. The presence or absence of Ala-1 on specific functional lymphocyte subsets was determined by treating the relevant cell population with anti-Ala-1 and complement, and assaying for residual functional activity. By this method Ala-1 was shown to be on in vivo primed killer T cells cytotoxic for allogeneic tumor cells [leukemia EL4 cells and mastocytoma P815 cells]. It was also found on helper T cells generated in vivo to sheep red blood cells, and on Ig[immunoglobulin]M and IgG plaque-forming cells (PFC) to sheep red blood cells. Splenic precursors of helper cells and of IgM PFC to sheep red blood cells were completely resistant to treatment with anti-Ala-1 and complement. Effector cells can be distinguished from their nonactivated precursors by their expression of Ala-1.