Heterogeneity of human T lymphocytes to bind sheep erythrocytes and mitogenic responses of their subpopulations.

Heterogeneity of human T lymphocytes was examined by the rosette formation of sheep red blood cells (E-rosette) in two different reaction media: fetal calf serum (FCS) and gelatin Veronal buffer (GVB). Nearly all the T lymphocytes could form rosettes in FCS at 1 degrees C (FCS-R) independently of the incubation time. In contrast, rosette formation in GVB (GVB-R) was apparently dependent upon the incubation time and could not be used in the enumeration of the total T cells even after long incubation. Among the possible subpopulations, a fraction (T1) that could form GVB-R as well as FCS-R, and the other fraction (T2) that could form only FCS-R were partially purified by rosette formation and by density gradient on a Ficoll-Isopaque layer. In contrast to the T cell-depleted fraction (B) which formed EAC rosettes in a majority of cells and E rosettes in a few cells, only a small portion of cells from both the T1 and T2 fractions could form EAC-rosettes. T1 cells possessed high responses to PHA as estimated by the counts of 3H-TdR incorporation as well as the stimulation indices. In contrast, T2 cells possessed a lower responsiveness to the mitogen, and B fraction cells could not respond at all. These results suggested that a positive correlation exists between the ability of E rosette formation and responsiveness to PHA in the T cell subpopulations. Preliminary experiments also suggested that percentages of T1 cells highly responsive to PHA may decrease and, therefore, those of T2 cells less responsive to the mitogen may increase in the T cell population of the patients with some immunodeficiencies.