LOSS OF NET NEGATIVE SURFACE-CHARGE DURING MLC STIMULATION OF HUMAN LYMPHOCYTES-T - CORRELATION TO STABLE E-ROSETTE FORMATION AND NATURAL ATTACHMENT TO NORMAL AND MALIGNANT TARGET-CELLS

Activation of human blood T [thymus-derived] lymphocytes in mixed lymphocyte culture (MLC) causes a reduction in the net negative surface charge as indicated by the reduction in the electrophoretic mobility. Concomitantly, the activated cells acquire new properties, including the ability to form stable E [sheep erythrocytes] rosettes and attach to normal and malignant cells of the same species (natural attachment (NA)). These properties were expressed by lymphocytes within the low electrophoretic fractions (cells with low negative charge) of the MLC populations. The formation of stable E rosettes and natural attachment capacities of human thymocytes correlated with the amount of surface negative charge. The slowly migrating (less negative charged) cortical thymocytes, which can form stable E rosettes, exhibit NA activity. Medullary thymocytes carrying a high net negative surface charge lack these characteristics. The reduction of negative charge during activation of peripheral T cells probably facilitates cell-to-cell contacts and prepares the (activated) cells to perform cooperative interactions with other cell types and express the lytic activity of T cells.