PRECIPITATED IMMUNE-COMPLEXES OF IGM INDUCE THE GENERATION OF REACTIVE OXYGEN SPECIES BY RABBIT POLYMORPHONUCLEAR LEUKOCYTES

We report that immune complexes of ISM (ICIgM) antibodies and ovalbumi n in the form of a precipitate from the equivalence zone induce the ge neration of reactive oxygen species by rabbit blood polymorphonuclear leucocytes (PMN), as measured by the chemiluminescence (CL) production in the presence of luminol. The kinetics of CL generation induced by ICIgM is quite different from that induced by precipitated immune comp lexes of IgG (ICIgG): the maximum rate of CL production for ICIgM occu rs around 14 min, whereas for ICIgG it occurs about 5 min after incuba tion with the cells. Also the triggering of the process requires a hig her concentration of ICIgM than of ICIgG. Evidence is presented that t hese effects are not mediated by interaction of the antigen (ovalbumin ) with the cell, since immune precipitates of ovalbumin and the F(ab') (2) fragment had no effect. Our observations that precipitated. ICIgM can also be an effective stimulus for CL generation and thus for O-2(- ) production reveal a new functional capability of PMN. These results may have implications for the understanding of the participation of IC IgM las well as of ICIgG) in inflammatory reactions mediated by PMN in immune complex diseases, and in the mechanisms of defense against mic robes and other non-self agents.