Paracrine rather than autocrine regulation of myeloma-cell growth and differentiation by interleukin-6.

Granulocyte-macrophage colony-stimulating factor synergizes with interleukin-6 in supporting the proliferation of human myeloma cells.

Mechanism whereby ouabain inhibits human T lymphocyte activation: effect on the interleukin 2 pathway.

Using in vitro-growing myeloma cell lines, we studied the growth factors involved in human multiple myeloma, and particularly the potential of autocrine secretion and response to B-cell growth factor (BCGF) of RPMI 8226, the best-documented Epstein-Barr virus-negative human myeloma cell line. We found that three myeloma cell lines (RPMI 8226, U266, and IM9) produce an autostimulatory growth factor (AGF) and thus increase their own proliferation by 2- to 3-fold in cells cultured at low density. Optimal AGF production was obtained after 24 h of culture at a cell density ranging from 2.5 to 5 million cells/ml. The three myeloma cell lines produce type II BCGF, able to induce the proliferation of highly purified human peripheral blood B-cells, only after anti-mu activation. The BCGF produced by RPMI 8226 can be absorbed onto RPMI 8226 cells together with the RPMI 8226 AGF, and the two are copurified on gel filtration in a peak with an apparent molecular weight of 70,000. RPMI 8226 can be efficiently activated by human high molecular weight BCGF II (Mr 50,000) and less extensively by BCGF I (Mr 12,000). RPMI 8226 does not produce either detectable IL1 or interferons gamma and alpha and IL1 and gamma-IFN had no stimulating effect on RPMI 8226 proliferation. Our findings support the conclusion that RPMI 8226 produces a BCGF II working as an AGF.

/pdf/production-of-growth-factors-by-human-myeloma-cells-2ei78tgoog.pdf

Production of growth factors by human myeloma cells.

The role of interleukin 1 and interleukin 2 in human T colony formation.

Phorbol myristate acetate (PMA) is a potent inducer of T colony formation by peripheral blood lymphocytes. A mean cloning efficiency of 0.3% (0.05-0.5%) is obtained with PMA concentrations of 100-1000 ng/ml. PMA-induced T colony formation does not require the presence of monocytes and therefore differs from other mitogens in this respect. Purified T-colony-promoting activity (TCPA) (devoid of phytohaemagglutinin (PHA)) increases PMA-induced T colony numbers and induces T colony formation at low PMA doses (0.01 to 1 ng), concentrations at which no T colonies are detected in the absence of added TCPA. PMA-induced colonies are mainly composed of cells bearing Fc receptors for IgM (54%), which is not the case for colonies obtained with PHA (11 %). PMA-induced colony cells do not bind OKT3 and OKT4 monoclonal antibodies, whereas 23% are able to bind OK-T8 antibody. These results demonstrate that PMA is a potent inducer of T colony formation and may therefore serve as a useful tool for the study of T-cell differentiation.

Induction of human T colony formation by phorbol myristate acetate.

Human T lymphocyte colonies may be grown in agar from pre-T peripheral blood cells. Pre-T cells giving rise to these colonies represent 0.5% of the non-adherent, E rosette and Leu 1 depleted mononuclear cell subpopulation. T colony formation is induced by PHA stimulation and only if media conditioned by PHA stimulated peripheral blood lymphocytes (PHA-LCM) is added. These media contained interleukin-2 (IL-2) and T colony promoting activity (TCPA) for pre-T cells. TCPA is co-eluted with IL-2 by gel filtration with an apparent molecular weight of 18,000 daltons. Moreover, when PHA-LCM are absorbed on IL-2-dependent cultured T cells, TCPA is removed as well as IL-2. In attempt to further demonstrate the role of IL-2 in T colony formation by the pre-T cells we used the anti-Tac monoclonal antibody directed against IL-2 receptor. We demonstrated that anti-Tac inhibits T colony formation in a dose-dependent manner in pre-T cells. We conclude that IL-2 is the essential exogenous factor contained in PHA-LCM which allows pre-T cell differentiation expression and proliferation in agar medium.

The role of interleukin-2 in T colony formation by human pre-T cells (pTCFC).

PMA (10 ng/ml), induced a four-fold increase in PHA-induced T colony formation by peripheral blood lymphocytes (PBL). At lower (0.1-1 ng/ml) and higher concentrations (100-1,000 ng/ml), PMA had an inhibitory effect. The potent co-mitogen effect observed at 10 ng/ml PMA was associated with a strong increase in T colony promoting activity (TCPA) released by PHA stimulated PBL cultured in the presence of PMA (10 ng/ml). PMA at all concentrations exerted an inhibitory effect on T colony formation when PBL were cultured in the presence of PHA and an optimal concentration of exogenous TCPA. PMA was also capable of assuming the essential role played by monocytes in T colony formation. Thus, PMA can fulfil both co-mitogen and monocyte like roles in T colony formation. These activities closely resemble those previously described for interleukin 2 (IL2) production.

Modulation of PHA-induced T colony formation by phorbol myristic acetate.

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The role of interleukin 1 and interleukin 2 in human T colony formation.

Induction of human T colony formation by phorbol myristate acetate.

The role of interleukin-2 in T colony formation by human pre-T cells (pTCFC).

Modulation of PHA-induced T colony formation by phorbol myristic acetate.