Enumeration of Absolute Numbers of T and B Lymphocytes in Human Blood

A new immunofluorescence test permits the direct enumeration of T and B lymphocytes in unseparated blood. B cells were identified with antiimmunoglobulin sera and T cells by a rabbit anti‐human brain serum rendered unreactive with B cells by sequential absorption with erythrocytes, liver, and either chronic lymphocytic leukaemia cells or a cell line, BRI‐8, with B‐cell surface characteristics. T and B cells were also enumerated with lymphocyte suspension purified by either Ficoll‐lsopaque density sedimentation or by a two‐step gelatin‐polystyrene bead column method. T cells in Ficoll‐purified suspension were also enumerated by rosette formation with sheep erythrocytes. Comparison of the T‐B proportions evaluated with the different cell preparation showed that the cell separation procedures can give rise to a deviation in the T:B ratio in favour of B cells. The extent of this induced bias related inversely to lymphocyte yield. Staining of whole blood preparations or high‐yield purified cells enables absolute numbers of T and B lymphocytes to be calculated. We consider this measurement considerably more informative than relative proportions of T and B cells.