Physicochemical characterization of chemotatic lymphokines produced by human T and B lymphocytes

Ostensibly pure populations of T and B lymphocytes were separated from peripheral human blood by a sequential rosetting method. These cells, and mononuclear leukocyte (MNL) cell preparations (60 to 85% T cells), were cultured in vitro and the supernatants of these cultures were assayed for chemotactic lymphokine (CTX) activity. B lymphocytes were activated to produce CTX by binding erythrocytes sensitized with antibody and complement (EAC) to their C3 receptors and phytohemagglutinin (PHA) stimulation of isolated T cells was used to produce T cell-derived CTX. Sephadex G-100 gel filtration chromatography of supernatants obtained from T and B cell cultures showed that both cell types produce a CTX of approximate molecular weight 12,500 daltons. This result is identical to that previously obtained in characterizing the CTX produced by buffy coat leukocytes. Isoelectric focusing of lymphocyte supernatants and chemotactically active Sephadex G-100 fractions showed that the CTX produced by B cells and PHA-stimulated MNL contained two peaks of lymphokine activity, a major peak at pH 10.1 and a minor peak at pH 5.6. Additionally, these studies show that the chemotactic complement peptide C5a has an isoelectric point of pH 8.7 and is antigenically distinct from T and B cell-derived CTX, although relatively homogenous by gel filtration, contain two isoelectrically distinct species. In addition, these findings suggest that T and B cells although possessing different membrane receptors and requiring different mechanisms of activation to initiate lymphokine synthesis, produce lymphokines with identical physiocochemical properties.