SEPARATION OF HUMAN LYMPHOCYTE-T SUB-POPULATIONS (T-MU, T-GAMMA) BY DENSITY GRADIENT ELECTROPHORESIS

Purified human peripheral blood T lymphocytes were fractionated by density gradient electrophoresis on the basis of their surface charge. The high mobility cell fractions were found to be enriched in T cells having receptors for IgM (Tμ cells) with only minor proportions of T cells having receptors for IgG (Tγ cells). In contrast, the low mobility cell fractions were enriched in Tγ cells with very low numbers of contaminating Tμ cells. Both populations were of higher mobility than human peripheral blood B lymphocytes. High-affinity sheep erythrocyte rosette-forming cells (E-RFC) were relatively enriched in the high and intermediate mobility fractions and appear to include the Tμ cells and the T cells without receptors for IgG or IgM (T∅). The low affinity E-RFC were found only in the lower mobility fractions that included the Tγ cell population. A direct correlation was observed between the number of Tγ lymphocytes and the low affinity E-RFC in all the fractions. The separated cell fractions were treated in vitro with different concentrations of concanavalin A (Con A) and examined for the numbers of Tμ and Tγ cells. Low concentrations of Con A (2.5 μg/ml) significantly increased the number of Tμ cells, whereas high concentrations of Con A (20 μg/ml and 40 μg/ml) markedly reduced the number of Tμ cells and increased the number of Tγ cells. Furthermore, all fractions (both Tμ and Tγ cell enriched) responded by proliferation to Con A, whereas only the high and intermediate mobility fractions (enriched in Tμ cells) responded to phytohemagglutinin. Fractions enriched in Tγ cells responded very poorly to phytohemagglutinin. This method provides another technique for separating human Tμ- and Tγ- enriched lymphocyte subpopulations and does not modulate the Fc receptors of the cells, in contrast to the rosetting techniques currently in use for the separation of these lymphocytes.