The Origin of Marginal-Zone Cells

The marginal zone is the outer compartment of the white pulp of mammalian spleens. Most cells found in this area are intermediate-sized lymphocytes (1,2). Surface marker analyses (3–6) have provided strong evidence that these cells are B lymphocytes. Also marginal zone lymphocytes are absent from the spleens of rats treated with heterologous anti-μ antibody from birth (6). In rat spleens marginal-zone B cells outnumber the B lymphocytes found in the follicles by a factor of two to three (6,7).