Migrant mu+ delta+ and static mu+ delta- B lymphocyte subsets.

Immunoglobulin isotype expression in isolated lymph node (LN), spleen and blood lymphocyte suspensions was assessed in rats. The proportion of mu+ delta- B cells in spleen (34%) was approximately twice that in blood and LN. Immunohistological examination of spleens showed the cells of the marginal zones to be predominantly mu+ delta-. On the other hand, mu+ delta+ B cells were mainly confined to the follicles in both spleen and LN. These follicles had a minor mu+ delta- component. The migratory properties of B cells with these two phenotypes were assessed by depleting lymphocytes migrating through the white pulp of rat spleen. This was achieved by placing a 32P-impregnated beta-emitting polythene strip over one half of the spleen. Examination of the nonirradiated half of the spleen, LN and peripheral blood after 12 days irradiation showed selective loss of delta + B cells. The mu + delta- cells of the splenic marginal zone were numerically unaltered. There was also a substantial residual mu + delta- B cell presence in the small lymphocyte compartment of follicles of LN and spleen in depleted animals. In addition, the blood selectively retained a mu + delta- B cell component. This was not derived from the spleen, as mu + delta- blood B cell numbers were sustained even where both halves of the spleen were irradiated. It is concluded that: (a) the major static B cell component of spleen and LN is mu + delta-, (b) that most if not all delta + B cells repeatedly migrate through the spleen and (c) there is a blood-born mu + delta- component which is resistant to depletion by splenic irradiation.,