CD300A

CD300A Full Name

CD300a molecule

CD300A Introduction

CD300A is a cell surface immunoregulatory receptor belonging to the CD300 family of immunoglobulin superfamily proteins. It is a single-pass type I membrane protein characterized by an extracellular Ig-like domain and an intracellular tail containing multiple immunoreceptor tyrosine-based inhibitory motifs (ITIMs). CD300a is widely expressed on both lymphoid and myeloid cells, including natural killer (NK) cells, T-cell subsets, B cells, dendritic cells (DCs), monocytes, mast cells, granulocytes and other leukocytes, where it functions principally as an inhibitory receptor that helps fine-tune immune responses by dampening activating signals. Its inhibitory capability is mediated through recruitment of phosphatases such as SHP-1/SHP-2 to ITIMs upon ligand engagement, facilitating down-regulation of downstream signaling pathways such as FcεRI and TLR-MyD88-mediated activation.

Figure 1. Schematic representation of human and mouse CD300a inhibitory receptor.(Sources: Zenarruzabeitia O, et al.; 2015)

Functionally, CD300a plays a crucial role in negative regulation of immune cell activation and inflammation. By recognizing aminophospholipid ligands such as phosphatidylserine and phosphatidylethanolamine that become exposed on apoptotic or activated cells, CD300a transmits inhibitory signals that restrain excessive cytolytic activity, cytokine release, and degranulation across diverse cell types, including NK cells, mast cells, eosinophils and neutrophils. This modulation of effector functions helps maintain immune homeostasis and prevents hyperinflammatory states, such as in allergic responses where CD300a can aid in the resolution of inflammation and promote recovery following insult. Moreover, CD300a expression influences adaptive immune processes—its presence on B cells can modulate B-cell receptor–mediated responses, and its levels on CD8+ T cells have been associated with qualitative aspects of antiviral immunity.

In terms of disease relevance, dysregulation or altered expression of CD300a has been implicated in inflammatory disorders, infectious diseases, autoimmune conditions and cancer. Its inhibitory signaling can limit pathological inflammation in models of arthritis and allergic disease, while in certain chronic infections such as HIV, altered CD300a patterns on lymphocytes and NK cells may affect immune control and cytotoxic responses. Importantly, CD300a has emerged as an immune checkpoint in the tumor microenvironment: tumors may exploit CD300a-mediated inhibition to suppress anti-tumor immunity, limit NK and DC function, and promote immune evasion. High CD300a expression in some hematologic malignancies like acute myeloid leukemia correlates with prognosis and potential immune escape, highlighting its relevance as both a biomarker and a therapeutic target in immuno-oncology and other diseases characterized by immune dysregulation.

Alternate Names for CD300A

CD300A; CD300a molecule; IRC1; IRC2; CLM-8; IRp60; IGSF12; CMRF35H; CMRF-35H; CMRF35-H

• 1. Zenarruzabeitia O, et al.; The Biology and Disease Relevance of CD300a, an Inhibitory Receptor for Phosphatidylserine and Phosphatidylethanolamine. J Immunol. 2015, 194(11):5053-60.