BDCA2BDCA4

BDCA2BDCA4 is an informal designation used in immunology to refer to the co-expression of two blood dendritic cell antigens, BDCA-2 (CD303, CLEC4C) and BDCA-4 (CD304, neuropilin-1), on human plasmacytoid dendritic cells (pDCs). BDCA-2 and BDCA-4 are part of the BDCA family, surface markers used to identify dendritic cell subsets in blood.

BDCA-2 is a type II transmembrane C-type lectin receptor, predominantly on pDCs. BDCA-4 is a transmembrane glycoprotein also known as neuropilin-1. In practice, BDCA-2 and BDCA-4 are widely used in flow cytometry to distinguish pDCs from myeloid dendritic cells and other leukocytes.

The co-expression of BDCA-2 and BDCA-4 is characteristic of pDCs, which specialize in rapid type I interferon production in response to viral nucleic acids. Functionally, BDCA-2 engagement can inhibit toll-like receptor 7/9 signaling and thereby reduce IFN-α production, acting as a regulatory brake. BDCA-4/CD304 is involved in ligand uptake and cell interactions; as neuropilin-1 it participates in signaling pathways in other cell types, though its precise roles on pDCs remain under study.

Clinically, pDCs and their BDCA markers are studied in health and disease, including viral infections, autoimmune conditions such as systemic lupus erythematosus, and cancer. BDCA-2 and BDCA-4 continue to be important tools for researchers profiling dendritic cells and for exploring targeted therapies.