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 role of these immunoglobulins in antigen-specific responses, and the examination of their functional properties would be greatly facilitated by the availability of monoclonal antibodies (Mabs) that distinguish between them. The production and characterization of two Mabs that recognize an IgG sub-isotype with the characteristics of IgG(ab) is described. The immunoglobulin identified by these Mabs had a heavy chain weight 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 analysis. In addition, one of these two Mabs (CVS1) also recognized the majority of peripheral blood B lymphocytes in indirect immunofluorescent staining analysis, suggesting either that equine IgD may share a common antigenic epitope with an IgG sub-isotype, or that a large proportion of equine B lymphocytes may express an IgG sub-isotype on their surface.