Interleukin 7 is a growth factor for mature human T cells

Abstract

We have studied the capacity of interleukin (IL) 7 to support the growth and expansion of human T cell clones of different phenotype and function. All the clones studied (CD4⁺CD8⁺, CD4⁻CD8⁻ T cell receptor α/β or γ/δ) responded to IL 7. The proliferative response of all the T cell clones induced by IL 7 was routinely less than to IL 2, but comparable to the IL 4 response. IL 7 also induced the proliferation of resting, freshly prepared peripheral blood mononuclear cells (PBMC) or T cell‐enriched (E⁺) cells. The pattern of proliferation observed in the presence of IL 7 was similar, but lower in magnitude, to that induced by IL 2. In both these cells populations the response to lymphokines alone was always less than the response to lymphokines plus insolubilized anti‐CD3 monoclonal antibody. In contrast IL 4 produced a different pattern of responsiveness, as significant proliferation was observed only on PBMC costimulated with anti‐CD3. The possibility that IL 7 mediates its growth stimulation by the IL 2 pathway was excluded by the incapacity of anti‐IL 2 or anti‐Tac monoclonal antibody, in concentrations which blocked IL 2‐dependent proliferation, to inhibit IL 7‐dependent growth. We conclude that IL 7 is a major growth factor for human mature T cells, and its activity is not limited to lymphocyte progenitors.