Different Requirements of CD3 Cross-Linkage for the Activation of Memory and Naive CD8+ T Cells

In the present experiments, the requirement of CD3 cross-linkage was studied in terms of activation of naive and Ag-primed CD8+ T cells in a murine system. The results showed that Ag-primed CD8+ T cells and both monoclonal and polyclonal T cell lines produced IL-2 by Fab anti-CD3 stimulation without cross-linkage in the absence of accessory cells. In contrast, naive T cells did not produce IL-2 in response to Fab anti-CD3 without participation of accessory cells; however, they produced IL-2 in the presence of accessory cells. These results indicate that the cross-linkage of CD3 molecules is not necessarily required for both naive and memory CD8+ T cells, but naive T cells, not memory T cells, require some interaction with accessory cells for IL-2 production in response to soluble monovalent anti-CD3.