IGM AND IGG DIRECT PLAQUE-FORMING CELLS DEVELOP DURING THE IMMUNE-RESPONSE OF MINIATURE SWINE TO SHEEP ERYTHROCYTES

A procedure for the direct determination of the class of antibody produced during the immune response of Minnesota miniature swine was developed by analyzing the distribution of Ig classes of direct hemolytic plaque-forming cells (PFC). The procedure involved cytoplasmic staining of fixed, direct PFC with class-specific fluorescent antibody reagents, utilizing the plaque assay methodology developed by Kennedy and Axelrad. Mean percentages of cytoplasmic IgM- and IgG-positive direct PFC determined during the immune response of conventional swine were found to be approximately 70% IgM positive and 30% IgG positive. Sheep red blood cell ghosts contained within the plaques stained positive for the same class of immunoglobulin as was expressed intracytoplasmically by the central PFC, indicating a specific correlation between cytoplasmic Ig class and the secreted class of antibody. Pronase treatment of spleen cells prior to assay, a procedure which removes surface Ig, produced no alteration in the frequencies of IgM- or IgG-positive direct PFC, indicating that our staining procedure was detecting genuine cytoplasmic Ig. The lack of significant overlap in the combined percentages of IgM- and IgG-positive PFC suggests that there should be few PFC producing antibody of both IgM and IgG classes simultaneously. © 1979.