The Isopaque-Ficoll method re-evaluated: selective loss of autologous rosette-forming lymphocytes during isolation of mononuclear cells from human peripheral blood.

A subpopulation of lymphocytes is defined, which--under conditions used for isolating mononuclear cells from peripheral blood by the Isopaque-Ficoll gradient--is lost to the erythrocyte pellet because of rosette formation with the autologous erythrocytes in the gradient. Reapplication of the resuspended erythrocyte pellet on a new gradient with higher density could, however, recover the subpopulation. Lymphocyte surface marker analysis on such cells showed that they were enriched in T cells (judged by rosette formation with sheep erythrocytes) and in autorosette-forming cells. The importance of these findings is discussed in relation to the wide use of the Isopaque-Ficoll method.