title: Study of some properties of the receptor for IgM on human lymphocytes.
abstract: Some properties of the receptor for IgM on human lymphocytes have been investigated. It was shown that the interaction of native IgM with the receptor present on T and B lymphocytes is not critical for its detection in the EAM-rosette assay. In fact, high values of EAM-RFC could be found on cell suspensions cultured overnight in either IgM-free or IgM-containing media. In addition, the inhibition of EAM-rosettes by human monoclonal IgM at 37 degrees C was not as effective as at 4 degrees C. Rabbit IgM showed a significantly greater ability to inhibit the binding of antigen-IgM antibody complexes than human IgM. The receptor for IgM was easily removed by handling procedures, the incubation of lymphocytes at 4 degrees C and treatment of the cells with low concentrations of trypsin or pronase. After the enzymatic treatment, a rapid resynthesis occurred, which restored the number of EAM-rosettes formed by T cells and significantly increased the number formed by B cells. The interaction between the receptor and antigen-IgM antibody complexes stopped the spontaneous shedding of the receptor at 4 degrees C. When the incubation of the cells with immune complexes was performed at 37 degrees C, a significantly different behaviour between T cells equipped with receptor for IgM and those possessing receptor for IgG was found. After the binding of EAG to the receptor for IgG, a process of rapid dissociation of rosettes occurred, whereas the incubation with EAM did not induce an irreversible loss of the receptor for IgM.
mesh_terms: D000936:Antigen-Antibody Complex; D002478:Cells, Cultured; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology*; D008214:Lymphocytes / Q000276:immunology*; D011961:Receptors, Fc / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism; D012397:Rosette Formation; D013601:T-Lymphocytes / Q000276:immunology; D013696:Temperature
chemical_list: D000936:Antigen-Antibody Complex; D007075:Immunoglobulin M; D011961:Receptors, Fc