Residual IgM Research Articles

Properties of a cell-bound homogeneous murine IgM anti-dextran—II. Reactions of cell-bound IgM with dextran and hapten

MOPC 104E is a murine myeloma IgM which reacts with dextran. A passive lysis system consisting of purified IgM bound to O-stearoyl dextran-coated sheep erythrocytes (IgM-OSD-E) and complement (C) was used to measure the effects of hapten and dextran on the properties of cell-bound MOPC 104E IgM. Incubation of IgM-OSD-E with the hapten nigerosyl- α(1→4) nigerose dissocaites IgM in proportion to hapten concentration (0·001 M hapten achieves 50 per cent dissociation). Lysis by C of such hapten-treated cells is directly proportional to residual cell-bound IgM. Concentration of dextran greater than 10 μg/ml dissociate IgM from IgM-OSD-E. The rate of dissociation by dextran is slower than that by hapten. Lower concentrations of dextran B1355S1, 3 bind to IgM-OSM-E without dissociation. The rate of binding is faster at 37°C than at 22°C, while no dextran binds to IgM-OSD-E at 0°C. Dextran bound to IgM-OSM-E inhibits lysis by C. Incubation of IgM with B1355S1, 3 prior to sensitization of OSD-E results in inhibition of binding, of IgM, in proportion to dextran to IgM ratio, with complete inhibition at ratios greater than 5.