Spin labeling studies of the interactions of P815 mouse mastocytoma cells with antiserum to histocompatibility antigens, H-2d.

The effect of antiserum to histocompatibility antigens on the membrane organization of murine neoplastic mast cells (P815) has been studied by spin labeling. Incubation of in vivo passaged cells, labeled with a nitroxide derivative of methyl stearate, with antiserum to membrane carried histocompatibility antigens, H-2d, resulted in an apparent decrease in membrane fluidity that was accompanied by histamine release. This electron spin resonance (esr) detectable change was found to be temperature, time, and dose dependent. Treatment of the cells with cytochalasin B, a drug disrupting microfilament structure, inhibited the effects induced by H-2d antiserum. In contrast, vinblastine, which disrupts microtubules, did not modulate the effect of this antiserum. Other data presented here suggest that some of the large spectral change observed on treatment of the cells with anti-H-2d serum may result from hydrolysis of the spin label fatty acid ester via activation of a membrane-associated esterase. The relationship of these results to other immunologically induced membrane phenomena is discussed.