Regeneration and tolerance factor is expressed during T-lymphocyte activation and plays a role in apoptosis

Regeneration and tolerance factor (RTF) is a protein cloned from the thymus and expressed on B lymphocytes in normal pregnancy, B lymphocytic leukemia lines, and T and B lymphocytes in individuals with HIV infection. Findings , using the Jurkat T-cell model, revealed chat RTF: is upregulated after ac tivation and anti-RTF antibody-induced apoptosis. In this article anti-RTF antibody-induced apoptosis of both unstimulated and activated T lymphocytes . RTF expression was examined in human PBMC or purified T lymphocytes after their in vitro activation. Kinetic studies indicated maximal RTF cell surf ace expression on activated T lymphocytes occurred between expression of th e early activation antigen CD69 and the IL-2 alpha receptor (CD25) by multi parameter Row cytometry. RTF receptor expression correlated with Fas (CD95) and CD25 receptor expression (r(2) = 0.6 and 0.5, respectively). RTF surfa ce expression was dependent on the stimuli used to activate T lymphocytes. T lymphocytes obtained maximal RTF expression when activated through the TC R signal complex using anti-CD3 epsilon antibody alone when compared with T lymphocytes activated with costimulation provided by anti-CD28 antibody al one or with anti-CD28 and anti-CD3 epsilon antibody. RTF is expressed under conditions of both activation and anergy. The RTFs increased concentration on the surface of anergic T cells may protect these cells from apoptosis b ecause increased RTF concentrations inhibited anti-RTF induced apoptosis. T hese data further characterize the expression of RTF on activated T lymphoc ytes and the role of anti-RTF antibody in T-lymphocyte apoptosis. Human Imm unology G, 577-588 (2001). (C) American Society for Histocompatibility and Immunogenetics, 2001. Published by Elsevier Science Inc.