Immunoglobulin bound in vivo to Fc receptor-positive cells in human central nervous system tumors.

Fifteen human central nervous system tumors of various histopathologic types were assessed qualitatively and quantitatively by indirect immunofluorescence for the presence of in vivo bound IgG, IgA, and IgM. The tumors were selected to reflect varying degrees of infiltration with Fc receptor-positive macrophages. The major purpose of the study was to determine the relative contribution of immunoglobulin (Ig) bound to tumor cells as compared to Ig bound to the Fc receptor-positive host macrophages. Of the 15 tumors, 1 tumor contained no detectable IgG, IgA, or IgM, 2 tumors contained only IgG and IgA bound in a smooth, homogeneous pattern to the surface of tumor cells, and 8 contained only IgG, IgA, and IgM attached to Fc receptor-positive cells. Four tumors contained significant numbers of tumor cells with cytoplasmic Ig, and two of those tumors also were infiltrated with Fc receptor-positive cells with membrane-associated Ig. Ig was removed from Fc receptor-positive cells but not from tumor cells by prolonged washing of sections of tumor at 37 degrees C, which suggested that Ig was associated with Fc receptors. That possibility was strengthened by the observation that the IgG subclass distribution of the Fc receptor-associated Ig was predominantly IgG1 and IgG3, whereas no predominant subclass existed for IgG bound to tumor cells. Furthermore, the Fc receptor-associated Ig appeared to be in the form of antigen-antibody complexes because it had a granular quality and because IgA and sometimes even IgM were involved in the Fc receptor-bound complexes.