Smyth Chicken Melanocyte Autoantibodies: Cross-Species Recognition,In Vivo Binding,and Plasma Membrane Reactivity of the Antiserum

Smyth line (SL) chickens, which develop a depigmenting disorder similar to human vitiligo, produce circulating anti-melanocyte antibodies (Austin, L.M. et al., (1992) The detection of melanocyte autoantibodies in the Smyth chicken model for vitiligo. Clin. Immunol. Immunopathol., 64:112–120). In order to characterize these autoantibodies, we studied the reactivity of cultured chicken, mouse, and human melanocytes, as well as frozen sections of chicken feather follicles and embryonic eyes, against SL serum, employing indirect immunofluorescence. Light Brown Leghorn (LBL) serum was used as a negative control. Chicken (SL and LBL), mouse, and human melanocytes exhibited greater fluorescence with SL serum than with LBL serum (up to a 1:60,000 dilution). The fluorescent pattern was predominant along the perimeter of the cells, suggesting plasma membrane staining. Fluorescence-activated flow cytometry analysis and immunocytochemical localization at the ultrastructural level using intact chicken cells supported this hypothesis. Melanocytes were readily stained in cryosections of regenerating feather follicles and embryonic eyes incubated with SL, but not LBL, serum. In addition, amelanotic melanocytes in albino chicken feathers reacted with SL serum. SL serum also preferentially stained cells emigrating from cultured avian neural tubes and within the dermis of the proliferative germ of regenerating feather follicles suggesting that melanoblasts express the antigens. We conclude that Smyth line serum contains melanocyte autoantibodies that cross-react with mouse and human melanocytes, are able to bind to pigment cells within tissues, and recognize antigens expressed in the cytoplasm and on the surface of melanocytes and melanoblasts.