HLA-Cw4 (Cw4) is a human leukocyte antigen serotype within HLA-C serotype group. Cw4 is determined by the antibody recognition of α4 subset of HLA-Cw α-chains. For the serotype Cw4, the alpha chain are encoded by the HLA-Cw*04 allele group and the β-chain are encoded by B2M locus. Cw4 and Cw*04 are almost synonymous in meaning. Cw4 is more common in Southeast Europe, where it is part of the Cw4-B35 haplotype.