FC RECEPTOR HETEROGENEITY - IMMUNOFLUORESCENT STUDIES OF B, T, AND 3RD POPULATION LYMPHOCYTES IN HUMAN-BLOOD WITH RABBIT IGG B4-ANTI-B4 COMPLEXES

  • 1 January 1977
    • journal article
    • research article
    • Vol. 119  (5) , 1778-1784
Abstract
Ig[immunoglobulin]G Fc receptors on human peripheral blood lymphocytes (PBL) were characterized by immunofluorescence studies with defined rabbit IgG b4 allotype/anti-allotype complexes. Three discrete types of Fc receptor-bearing cells, totaling .apprx. 33% of PBL, were identified. Fc receptors of the 3 types differed in their sensitivity to trypsin and in either absolute or localized density (topography) as determined by variable requirements for anti-IgG cross-linking in order to visualize bound complexes microscopically. The question of additional heterogeneity related to differences in individual Fc receptor affinity for complexed IgG was not approached in this study. Ten to 15% of PBL had pronase-sensitive, trypsin-resistant Fc receptors readily detected by direct immunofluorescence by using large fluorescein-conjugated complexes prepared near equivalence. Double-label and lymphocyte fractionation experiments established this population to be largely distinct from surface IgM + B [bone marrow derived] cells and T [thymus derived] cells, and identical to EARipley [erythrocyte-antigen] rosette-forming cells. Approximately 50% of surface IgM + B cells and .apprx. 10% of T cells had lower density Fc receptors identified by indirect immunofluorescence with small complexes prepared in antigen excess or by cross-linking fluorescein-conjugated complexes with anti-rabbit IgG anti-serum. An additional .apprx. 15% peripheral T and B cells had very low density Fc receptors detectable by complexing the IgG on the cell surface by sequential incubations of cells with b4 IgG and anti-b4. Fc receptors on B and T cells were sensitive to both pronase and trypsin digestion. The heterogeneity of IgG Fc receptors on different lymphocyte subpopulations as defined by these experiments may be of relevance for further analysis of normal and abnormal immune function.