B-cells play an important role in protection against pathogens, and they secrete specific antibodies in serum and mucosal secretions upon antigenic stimulation contributing to immune exclusion and clearance of pathogens. The frequency of antibody forming cells (AFC) in specific organs is often a reflection of the route of antigen exposure, i.e., systemic, oral, or intranasal, as well as of antigenic load. Enumeration of AFC was originally performed by plaque-forming cell assay measuring lysis of sheep red blood cells. The nature of this assay, that requires coupling of the antigen to sheep red blood cells (SRBC), made detection of various antigen-specific AFC rather cumbersome. However, the development of the enzyme linked immunodetection of AFCs (ELISPOT) combined with the development of standardized lymphocyte isolation techniques enables detection of AFC secreting antibodies specific for many different antigens and derived from various immunologic effector sites (1-6).