HUMORAL IMMUNOSTIMULATION .8. INCREASED INCORPORATION OF PHOSPHATE AND TURNOVER OF PHOSPHATIDYLINOSITOL IN CELLS TREATED WITH ANTIBODY

  • 1 January 1977
    • journal article
    • research article
    • Vol. 119  (3) , 911-917
Abstract
Uptake of phosphate (32P) in [mouse fibroblast] L cells was modulated by reaction with anti-L cell antibody. A biphasic response was noted with high, cytotoxic concentrations inhibiting 32P uptake and low, cytostimulatory concentrations stimulating 32P uptake. Stimulation of 32P uptake was dependent upon multivalent binding as immune Ig[immunoglobulin]G and F(ab'')2 were effective, but univalent Fab'' was ineffective in enhancing 32P uptake into cells. Antibody stimulation of 32P uptake appeared to be an energy independent process and to take place by activation of 32P membrane transport with an increased Vmax (19.3 pmol/min to 25.3 pmol/min), but the same Km (0.22 mM). Isolation and measurement of cellular (primarily membrane) phospholipids demonstrated a dramatic increase of (2-fold) specific radioactivity phosphatidylinositol. Early turnover of phosphatidylinositol may be an important signal for tumor cells to grow at an enhanced rate when exposed to cytostimulatory concentrations of antibody.