title: Effects of transforming growth factor-beta on human lymphokine-activated killer cell precursors. Autocrine inhibition of cellular proliferation and differentiation to immune killer cells.
abstract: With subpopulations of human lymphoid cells that were enriched for lymphokine-activated killer (LAK) cell precursors, studies were performed to examine the effects of transforming growth factor-beta (TGF-beta) on their IL-2-dependent growth and differentiation to killer cells. The majority of the LAK precursor cells appeared to reside in nonadherent, non-T, and non-B lymphocyte populations that expressed CD11 and CD16 Ag. These cells were induced to proliferate and become LAK cells by high concentrations of rIL-2 alone in the apparent absence of any prior activation with mitogen or Ag. The partially purified lymphocyte subpopulations generated varying but several-fold greater levels of LAK killing on a per cell basis than did unfractionated lymphocytes. The exogenous addition of TGF-beta to the LAK precursor cultures, markedly inhibited IL-2-stimulated growth as well as the development of LAK activity in a dose-dependent manner. The antimitotic effect of TGF-beta was reversible; inhibition of proliferation could be largely restored by increasing the concentration of IL-2 in culture. In contrast, TGF-beta inhibition of cytotoxicity was relatively independent of the concentration of IL-2. Further, LAK precursors constitutively expressed TGF-beta mRNA and high affinity receptor for TGF-beta. Activation of LAK precursors with IL-2 alone, resulted in a three- to fivefold up-regulation of intracellular TGF-beta mRNA and TGF-beta biologic activity secreted in the culture media. Furthermore, Northern blotting revealed that the resting LAK precursors did not express the Tac-mRNA. Receptor binding studies with 125I-IL-2 suggested the presence of a single class of IL-2R with an apparent Kd of intermediate range (beta-chain of IL-2R) on the unstimulated cells. Stimulation with high concentrations of Il-2 induced Tac-mRNA (both the 3.5- and 1.5-kb transcripts) and resulted in the expression of high affinity IL-2R (Kd approximately 10(-11) M) on these cells. Suppression of IL-2-dependent responses by TGF-beta was accompanied by a selective down-regulation of the 1.5-kb Tac-mRNA as well as by reduction in high affinity IL-2R. The results suggest a negative autocrine control of TGF-beta on IL-2-dependent growth and differentiation of human LAK cells, possibly related to regulate the killer activation function.
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D006131:Growth Inhibitors / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000502:physiology; D007376:Interleukin-2 / Q000378:metabolism / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D010455:Peptides / Q000378:metabolism / Q000502:physiology*; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000187:drug effects; D015375:Receptors, Interleukin-2; D015291:Transforming Growth Factors
chemical_list: D006131:Growth Inhibitors; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D010455:Peptides; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D015291:Transforming Growth Factors