IL 2 alone is mitogenic only for Tac-positive lymphocytes in human peripheral blood.
To investigate the ability of interleukin 2 (IL 2) alone to induce proliferation of resting human lymphocytes, we stimulated human peripheral blood mononuclear cells (PBMC) with an immunopurified preparation of IL 2 or with phytohemagglutinin (PHA). Proliferation and the percent of cells expressing IL 2 receptors were assessed over 6 days of culture. Regardless of the stimulus, the percent of cells bearing an IL 2 receptor paralleled the amount of proliferation, and proliferation was inhibited by an anti-IL 2 receptor monoclonal antibody (anti-Tac). When stimulated by IL 2 alone, less than 8% of PBMC expressed an IL 2 receptor after 24 hr of culture. Stimulation by IL 2 caused both proliferation and IL 2 receptor expression to increase over the entire culture period (routinely to 75,000 cpm and 50% respectively). When colchicine was added (to inhibit cell division), the percent of cells bearing an IL 2 receptor did not increase. IL 2 alone also induced proliferation of PBMC depleted of accessory cells, with the same kinetics but reduced peak response. Both accessory cells and supernatants that showed IL 1 but not IL 2 activity augmented this proliferation 50 to 100%. In contrast to the effect of IL 2, 25 to 50% of PBMC stimulated by PHA expressed an IL 2 receptor after 24 hr of culture. PHA-induced proliferation and IL 2 receptor expression peaked early in the culture period (routinely to 100,000 cpm and 50% respectively within 3 days), and colchicine did not inhibit the early induction of IL 2 receptors on PBMC. Our findings indicate that unlike PHA, IL 2 induces proliferation of PBMC (or PBMC depleted of accessory cells) by expanding the small percentage of cells in a resting population that already express IL 2 receptors. IL 2 does not appear to induce IL 2 receptors on cells previously lacking this molecule. We also find that IL 1 can enhance the response to IL 2 alone.
D000938:Antigen-Presenting Cells / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology*; D002448:Cell Adhesion; D002469:Cell Separation; D006801:Humans; D007375:Interleukin-1 / Q000502:physiology; D007376:Interleukin-2 / Q000378:metabolism / Q000502:physiology*; D008213:Lymphocyte Activation; D011971:Receptors, Immunologic / Q000096:biosynthesis / Q000502:physiology; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
D000954:Antigens, Surface; D007375:Interleukin-1; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7