Correlation analysis between frequencies of circulating antigen-specific IgG-bearing memory B cells and serum titers of antigen-specific IgG

Recent studies in mice have indicated that the long-lasting specific antibo dy responses seen after vaccination are probably due to the existence of lo ng-lived plasma cells. Therefore, because the maintenance of humoral immuni ty does not necessarily reflect continuous restimulation of long-lived memo ry B cells, the question arises as to what degree antibody immunity, as det ermined by measuring serum immunoglobulin titers against a particular antig en, and memory B cell immunity, as determined by counting circulating memor y B cells with specificity for that same antigen, correlate. Here, using a new assay combining two-step immunomagnetic enrichment with multiparameter flow cytometry to detect, enumerate and characterize antigen-specific memor y B cells, we show for tetanus toxin C-fragment in blood of normal tetanus toroid vaccinized donors, and for wasp venom phospholipase A, B in blood of wasp venom-allergic donors undergoing an immune therapy with wasp venom, t hat there is no statistically significant linear correlation between the fr equencies of circulating antigen-specific IgG-bearing memory B cells and th e serum titers of antigen-specific IgG. This lack of a statistically signif icant linear correlation is in accordance with the idea that B memory cells and plasma cells represent independently controlled forms of immunological memory.