HUMORAL IMMUNOSTIMULATION .6. INCREASED CALCIUM-UPTAKE BY CELLS TREATED WITH ANTIBODY AND COMPLEMENT

  • 1 January 1976
    • journal article
    • research article
    • Vol. 117  (3) , 973-980
Abstract
When [mouse fibroblast] L cells were treated with [rabbit] anti-L cell antibody in medium depleted of complement [C], rapid increases in Ca2+ uptake were obtained over a wide range of antiserum concentrations. Concomitant cell growth and viability studies demonstrated that stimulation of cell growth occurred at higher dilutions of antiserum, whereas cytotoxicity occurred at lower dilutions. The stimulatory and toxic effects of antibody on cell growth were potentiated by C as was the enhancement in Ca uptake. Sera deficient in C1r [r fragment of the 1st C component], C2, 4d, C4, C3-C9 did not increase the Ca uptake response to antibody, whereas augmentation occurred with C6-deficient serum. A specific role for C was further indicated by the ability of purified C components to restore the response to C in C-deficient sera. C3 with C3-C9 deficient serum, but not C2, C5, and C6 with C3-C9 deficient serum restored augmentation effects. Thus, C augments Ca2+ and nucleoside uptake; the effect is primarily via the classical C pathway through C3. Substrate saturation studies demonstrated that antibody activated the facilitated diffusion of Ca2+ altering the Vmax but not the Km of transport, whereas addition of complement altered both the Vmax and Km. One of the early effects of enhancing antibody upon tumor cell metabolism in vitro is apparently to stimulate uptake of Ca2+. In view of the suspected role of Ca2+ in cell proliferation the increase in cell-associated Ca++ may be important in the subsequent proliferative response.

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