PRKCQ is a calcium-independent, novel isoform that is important in transducing signals in T lymphocytes. Interaction of a T lymphocyte with an antigen-presenting cell results in clustering of the T cell antigen receptor (TCR) and the recruitment of a large signaling complex to the site of cell-cell contact. PRKCQ is essential for TCR-mediated activation. PKC theta plays a role in pathways that link the TCR signaling complex to the activation of NF-kappa B in mature T lymphocytes.