Vitiligo is a common depigmenting skin disorder resulting from the loss of melanocytes in the cutaneous epidermis. Although the cause of the disease remains obscure, autoimmune mechanisms are thought to be involved. Recently,
melanin-concentrating hormone receptor (MCHR)-binding
autoantibodies have been identified in
vitiligo patients. In the present study, we aimed to determine if MCHR
autoantibodies could also affect receptor function either by direct activation or by blocking its response to
melanin-concentrating hormone. The results indicated that 10/18 (56%)
vitiligo patient
IgG samples inhibited the function of MCHR expressed in a Chinese hamster ovary cell line. In contrast, neither control (n=20) nor SLE patient (n=10)
IgG samples blocked receptor function. Compared with healthy controls, MCHR function-blocking
autoantibodies were found at a significantly increased frequency in the
vitiligo patient group (P=0.0004). No MCHR-activating
autoantibodies were detected in any of the
vitiligo patient, SLE patient or control
IgG samples that were analysed. In addition,
vitiligo patient IgGs were tested for MCHR
autoantibodies that could mediate antibody-dependent cell-mediated cytotoxicity via the receptor. However, this could only be demonstrated in two
vitiligo patient sera. Overall, this work has provided additional evidence that MCHR is a B-cell
autoantigen in
vitiligo and has demonstrated the existence of MCHR function-blocking
autoantibodies further to the receptor-binding
autoantibodies previously reported.