OKT 3-activated locomotion of human blood lymphocytes: a phenomenon requiring contact of T cells with Fc receptor-bearing cells.

The OKT3 antibody activates locomotion of human blood I lymphocytes as measured by polarization assays and invasion of collagen gels. The proportion of motile cells increases during a period of 24-48 hr of culture, even following only a brief initial contact with OKT3. The motile cells are the growing population. Locomotion activation is cell-density dependent. Studies with surface- bound mitogens, namely substratum-bound 0K13 and Con A-Sepharose, showed that only lymphocytes in direct contact with the mitogen acquired locomotor capacity. Those separated from it by a cell-impermeable filter were not activated. The response to OKT3 requires the whole antibody molecule. F(ab')₂ fragments were inactive. Intact normal human IgG, but not its F(ab')₂ fragments, blocked the response. Removal of RFcγ + cells from the population by rosetting with IgG-Ab-coated sheep red cells prevented the response. These findings suggest that an RFcγ + population has to be present for T cells to become activated to locomotion by OKT3, and that the OKT3 antibody links the T cell to an FcR + cell, cell-to-cell contact being essential for activating the locomotor response. [ABSTRACT FROM AUTHOR]