The tetraspan MS4A family in homeostasis, immunity, and disease

The membrane-spanning 4A (MS4A) family includes 18 members with a tetraspan structure in humans. They are differentially and selectively expressed in immunocompetent cells, such as B cells (CD20/MS4A1) and macrophages (MS4A4A), and associate with, and modulate the signaling activity of, different classes of immunoreceptor, including pattern recognition receptors (PRRs) and Ig receptors. Evidence from preclinical models and genetic evidence from humans suggest that members of the MS4A family have key roles in different pathological settings, including cancer, infectious diseases, and neurodegeneration. Therefore, MS4A family members might serve as candidate biomarkers and therapeutic targets for various conditions.