The immune adaptor ADAP plays a pivotal role invariant natural killer T cell functions

Abstract

Abstract Invariant natural killer T cells (iNKTs) comprise a sub-lineage of T lymphocytes that express an “invariant” T cell receptor (TCR) with specificity for glycolipid antigens (Ag) such as a-galactosyl ceramide (aGC), when presented in complex with the MHC class I molecule CD1d. Following TCR engagement, iNKTs rapidly secrete cytokines and trans-activate the anti-tumor functions of dendritic cells (DC), natural killer (NK), T and B cells as well as directly kill tumor cells. Based on their dual functions as potent cytokine producers and tumor killers, iNKTs serve as a powerful tool for use in cell-based immunotherapies for cancer. Although TCR-CD1d interactions are generally required for iNKT cell functions, the signaling mechanisms that co-operate with the TCR to promote maximal iNKT cell responses remain poorly understood. Our previous studies demonstrate that the adaptor protein SAP and its signaling partner, Fyn (a Src-tyrosine kinase) is critical for iNKT cell functions. We recently investigated the role of ADAP (adhesion and degranulation promoting adaptor protein), a Fyn-binding protein in iNKT functions. We observe that aGC-induced iNKT cell activation, cytokine production, and bystander immune cell activation as well as anti-tumor response are remarkably reduced in ADAP-deficient (Adap−/−) mice. These data suggest that ADAP is a critical regulator of Ag-induced iNKT cell functions. Studies are currently underway to elucidate the mechanism(s) by which ADAP regulates iNKT cell functions. These studies will have an impact by establishing new paradigms for iNKT cell signaling and offering insights into how iNKTs can be best activated to enhance host immunity and treat cancer.