MONOCLONAL-ANTIBODIES SPECIFIC FOR EQUINE IGG SUB-ISOTYPES INCLUDING AN ANTIBODY WHICH RECOGNIZES B-LYMPHOCYTES

Equine immunoglobulin G is currently classified as consisting of five sub-isotypes: IgGa, b, and c, IgG(T), and IgG(B). The study of the rol e of these immunoglobulins in antigen-specific responses, and the exam ination of their functional properties would be greatly facilitated by the availability of monoclonal antibodies (Mabs) that distinguish bet ween them. The production and characterization of two Mabs that recogn ize an IgG sub-isotype with the characteristics of IgG(ab) is describe d. The immunoglobulin identified by these Mabs had a heavy chain weigh t of 53 kDa, was of rapid cathodal electrophoretic mobility in immuno- electrophoretic analysis, and reacted only with anti-sera to IgG, and not with anti-sera to IgG(T), IgA, or IgM in radial-immunodiffusion an alysis. In addition, one of these two Mabs (CVS1) also recognized the majority of peripheral blood B lymphocytes in indirect immunofluoresce nt staining analysis, suggesting either that equine IgD may share a co mmon antigenic epitope with an IgG sub-isotype, or that a large propor tion of equine B lymphocytes may express an IgG sub-isotype on their s urface.