Alterations in blood leukocyte populations in Smyth line chickens with autoimmune vitiligo

Smyth line (SL) chickens spontaneously develop a posthatch autoimmune loss of pigment cells (vitiligo) in the feather. Concurrent with the development of Smyth line vitiligo (SLV), mononuclear cell infiltration and altered T cell profiles can be observed in the pulp of developing feathers. To determine whether the development of SLV is preceded by or associated with alterations in blood lymphocyte and leukocyte populations, blood leukocyte profiles were established at various times prior to and throughout the spontaneous development of SLV. The proportions among various blood leukocyte populations (percentage of lymphocytes, monocytes, heterophils, eosinophils, and basophils) were determined by differential leukocyte counts. The proportions among blood lymphocyte populations were examined by immunofluorescence and flow cytometric analyses. Lymphocyte markers included fluorescence-conjugated monoclonal antibodies to identify T cells (CD3), T helper cells (CD4), cytotoxic T cells (CD8), and B cells (IgM). The proportions among blood lymphocyte populations examined did not differ between SL and MHC-matched parental Brown Line (BL) control chickens prior to and throughout the development of SLV. Compared to BL controls, SL chickens had, however, increased proportions of inflammatory leukocytes in the blood, particularly at the time when most hatchmates developed SLV. Examination of leukocyte alterations with respect to first observation of SLV revealed that inflammatory leukocyte levels were elevated early in SLV. Although altered leukocyte profiles in the blood were observed during the development of SLV, blood from SL chickens did not reflect alterations in lymphocyte populations known to occur at the site of melanocyte destruction. The role of inflammatory blood leukocytes in the development of SLV needs to be further investigated.