The Path of Memory B‐Cell Development

Germinal centers (GC) form in lymphoid tissue draining a site of soluble antigen injection, starting approximately on day 4 and reaching peak development by d 10 after the injection. Many investigators have observed that the maximal deveiopment of GC after injection of soluble antigen comes later than the peak ofantibody production (White 1960, Langevoort et al. 1963. Coico et al. 1983). Sites ofantibody production in various tissues, but particularly in the spleen of the rabbit where it was examined in detail, are invariably associated with sites of accumulation of proliferating plasma blasts and plasma cells. In the spleen, these are found at the border of white and red pulp and along penicilli arterioles extending from the white into the red pulp (Fig. 1; Thorbecke & Keuning 1956, Langevoort et al. 1963). Both histologicai demonstration of the antibody by immunofluorescence (Leduc et al. 1955) or immunoperoxidase (Sordat et al. 1970). and production ofantibody in tissue culture have clearly identified plasma cell aggregates as the major antibody-producing foci. Compartmentalization of GC and plasma cell foci also occurs in lymph nodes draining sites of antigen injections. GC are in the outer part ofthe cortex, while maturing plasmabiasts, again arising earlier than the GC. move from the dense lymphoid areas of the cortex to the medullary cords during the response (Nieuwenhuis &. Keuning 1974, Jacobson et al. 1974).