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

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Abstract
Recent studies in mice have indicated that the long‐lasting specific antibody responses seen after vaccination are probably due to the existence of long‐lived plasma cells. Therefore, because the maintenance of humoral immunity does not necessarily reflect continuous restimulation of long‐lived memory B cells, the question arises as to what degree antibody immunity, as determined by measuring serum immunoglobulin titers against a particular antigen, and memory B cell immunity, as determined by counting circulating memory 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 memory B cells, we show for tetanus toxin C‐fragment in blood of normal tetanus toxoid vaccinized donors, and for wasp venom phospholipase A1B in blood of wasp venom‐allergic donors undergoing an immune therapy with wasp venom, that there is no statistically significant linear correlation between the frequencies of circulating antigen‐specific IgG‐bearing memory B cells and the serum titers of antigen‐specific IgG. This lack of a statistically significant linear correlation is in accordance with the idea that B memory cells and plasma cells represent independently controlled forms of immunological memory.