Identification and characterization of subpopulations of lymphocytes in human peripheral blood after fractionation on discontinuous gradients of albumin

cytes were separated on discontinuous gradients of 17-35 % bovine serum albumin (BSA) into nine fractions. Three subpopulations of lymphocytes were obtained. One occupies the top third of the gradient (fractions 1-3, 17-23 % BSA) and is rich in cells characterized by a high spontaneous rate of DNA synthesis and by the ability to give rise to colony-forming units. The middle portion of the gradient (fractions 4 and 5, 23-27 % BSA) is rich in thymus-derived (T) lymphocytes identified by their vigorous response to mitogens and by their ability to form rosettes with sheep erythrocytes (E). The third subpopulation at the bottom of the gradient (fractions 6-9, 27-35 % BSA) is rich in bone marrow-derived (B) lymphocytes capable of staining with fluorescent anti-immunoglobulin antisera and of forming rosettes with EAC1423. The peripheral blood lymphocytes of five boys with proved X-linked agammaglobulinemia and two with prob-able X-linked agammaglobulinemia were found to be totally deficient in B lymphocytes (fractions 6-9) and lacked the subpopulation identified by immunofluorescent staining or rosette formation with EAC1423. One boy with proved X-linked agammaglobulinemia and two with probable X-linked agammaglobulinemia possessed a nor-mal amount of circulating B lymphocytes. Dr. Geha is the recipient of a postdoctoral fellowship fro