Role of SLAM Family Receptors and Specific Adapter SAP in Innate-Like Lymphocytes

Innate-like lymphocytes, which comprise an integral part of the immune system, possess unique developmental and functional capabilities that set them apart from conventional T and B lymphocytes. Strategically located to act as a first line of defense against pathogens, they behave as innate cells. To efficiently perform their innate functions, these populations are endowed with common phenotypic characteristics that include the expression of semi-invariant TCR or BCR and activation/memory cell markers. Moreover, they have the capacity to rapidly respond to pathogenic threats and the ability to ignite adaptive immune response in synchrony with myeloid cells. Indeed, all of these common features mirror a shared molecular program, in which Signaling Lymphocytic Activation Molecule Family (SLAMF) receptors and their cytoplasmic binding partner, the adapter signaling lymphocytic activation-associated protein (SAP), play a crucial role. Despite the extensive characterization of SLAMF molecules as a group of cell-surface receptors that regulate and interconnect both innate and adaptive immune cells, their relevance in innate-like lymphocyte ontogeny and physiology has recently taken center stage. Here, we review the current understanding of the roles SLAMF receptors and SAP adaptor molecules play in the biology of innate-like lymphocytes.