- Systemic immunization can elicit a significant response of IgG producing activated B cell subsets in human blood, part of which is not toward the vaccine. However, the effect of vaccination on IgA antibody secreting B cell subsets has had limited investigation. We immunized healthy, adult volunteers with a tetanus/diphtheria vaccine and observed a significant burst of IgA-secreting pre-plasma cells (PPC). Isolated PPC produced IgG, but not IgA antibody to tetanus antigen, and produced IgA and IgG antibody specific for poliovirus and herpes simplex virus. Thus, a vaccine that generates a systemic recall response to tetanus also induces blood PPC secreting IgA and IgG antibody relevant to mucosal protection.