RECEPTORS FOR IGM ON HUMAN-LYMPHOCYTES .3. SPECIFICITY OF RECEPTORS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 37  (3) , 495-501
Abstract
Receptors for the Fc portion of Ig[immunoglobulin]M (RFc.mu.) can be detected on a large percentage of human peripheral lymphocytes. To approach an understanding of the function of these receptors the relative efficiencies of different preparations of human IgM and their F(c)5.mu. fragments in binding to RFc.mu. were examined. This was measured by blocking rosette formation between lymphocytes and IgM-sensitized ox erythrocytes (EA.mu.). IgM from pooled normal human serum completed blocked formation of IgM rosettes (EA.mu.-RFC) at much lower concentrations than IgM preparations from individual Waldenstrom''s macroglobulinemic patients (WM). The differences in effectiveness of these IgM preparations in inhibiting EA.mu.-RFC suggested the existence of receptors for subclasses of IgM on different subpopulations of human lymphocytes. F(c)5.mu. fragments of IgM were more effective in blocking EA.mu.-RFC than the parent molecule, which was in turn more efficient than the 8S subunit. F(c)5.mu. may have more Fc regions exposed/molecule for binding to the matrix of RFc.mu. than pentameric IgM. Fc multivalency may be important for the stable binding of IgM or RFc.mu.