DISTINCT RECIRCULATING AND NON-RECIRCULATING B-LYMPHOCYTE POOLS IN THE PERIPHERAL-BLOOD ARE DEFINED BY COORDINATED EXPRESSION OF CD21 AND L-SELECTIN

The continual recirculation of lymphocytes between the blood, tissues, and lymph is essential for the coordination and dissemination of immu ne responses. We have compared the functional and phenotypic propertie s of lymphocytes isolated from brood and lymph, the two major migrator y populations. Lymph-borne lymphocytes migrated readily into the lymph atic recirculation pathway, but greater than one third of all peripher al blood lymphocytes (PBLs) were excluded from the lymphatic circuit a nd showed an enhanced migration to the spleen. Phenotypic analysis sho wed that most non-recirculating PBLs were B cells. The migration compe tence of B cells correlated with the surface expression of CD21 and L- selectin; recirculating B cells expressed both of these molecules. whe reas non-recirculating B cells lacked both antigens. These results est ablish that blood contains distinct pools of lymphocytes that differ i n their recirculation competence. Clearly, blood sampling is not an ef ficient method to directly measure the status of the recirculating imm une system, and implies important constraints and restrictions in the interpretation of experimental or clinical data that include phenotypi c and quantitative analyses of blood lymphocytes. (C) 1997 by The Amer ican Society of Hematology.