The signaling lymphocytic activation molecule (SLAM) family of receptors (SLAMF) is a group of receptors belonging to the CD2 family. It is composed of several members expressed on many hematopoietic cells. Most of the receptors interact in a homophilic fashion with neighboring cells. Their distribution and binding properties, together with their ability to function as both activating and inhibitory receptors, put them as key players in the immune system regulation. Several SLAM family receptors have been extensively investigated. This review mainly focuses on CD244 (2B4 or SLAMF4,) and CD48, particularly as expressed by the key cells of allergy, mast cells and eosinophils.