Melanocyte-specific cell mediated immune response in vitiliginous Smyth line chickens

Smyth line chickens (SL) are an animal model to study human autoimmune vitiligo. Vitiligo in SL chickens is characterized by a post-hatch loss of feather melanocytes (MC) resulting in feather depigmentation. The etiopathology of this disease remains unclear, however, a hypothesis that cell-mediated immunity (CMI) plays an important role in the destruction of melanocytes has been proposed based on previous studies. To support this hypothesis, the delayed wattle response (DWR) to MC lysates was examined in SL chickens and normally pigmented, MHC-matched controls (Brown line, BL; Light Brown Leghorn, LBL) to determine whether vitiliginous SL chickens have MC-specific CMI. Chickens were challenged in one wattle with a lysate of either embryo- or feather-derived cultured MC. Lysates of chick-embryo-fibroblasts (CEF) associated turkey herpesvirus (HVT) vaccine and syngeneic CEF were used as positive and negative control, respectively. Vitiliginous SL chickens exhibited a significantly greater DWR to feather-MC but not to embryo-MC and CEF than nonvitiliginous SL chickens and normally pigmented controls. The DWR to feather-MC peaked at 3 to 5 days post feather-MC lysate injection. Immunohistochemical staining of DWR-positive wattle tissue revealed extensive lymphocyte infiltration at the site of feather-MC injection consisting primarily of T cells (TCR2+, CD4+ or CD8+ T cells). These observations support the presence of MC-specific CMI in SL chickens with vitiligo. The anti-MC CMI activity appears to be specific to MC derived from feathers. SDS-PAGE analysis of different sources of MC lysates revealed a 43 kDa missing band in the lysate of feather-MC established from SL chickens. No other obvious protein pattern differences that could account for the feather MC-specific CMI response in vitiliginous SL chickens were observed among the MC lysates.