T cells in regenerating feathers of Smyth line chickens with vitiligo.

Smyth line (SL) chickens exhibit a spontaneous, autoimmune, depigmentation (SL vitiligo, SLV) in regenerating feather tissue due to the death of pigment cells (melanocytes). It was the purpose of this study to characterize mononuclear leukocytes which infiltrate the feather as SLV develops. Frozen sections of regenerating features from SL and control chickens were labeled with a panel of mAbs specific for chicken mononuclear leukocytes. SL chickens were found to have significantly greater numbers of T cells in the feather pulp prior to, and throughout, the development of SLV. Initially, both SL and control chickens had a CD4/CD8 ratio near 1.0 in their feather pulp. Following the onset of SLV, the CD4/CD8 ratio in SL chickens dropped below 0.4. Throughout the development of SLV, SL chickens had greater proportions of T cells with alpha/beta T cell receptors than controls. Histological evidence strongly supports an important role for T cells in the pathology of SLV.