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 d evelopment 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 popul ations, blood leukocyte profiles were established at various times pri or to and throughout the spontaneous development of SLV. The proportio ns among various blood leukocyte populations (percentage of lymphocyte s, monocytes, heterophils, eosinophils, and basophils) were determined by differential leukocyte counts. The proportions among blood lymphoc yte populations were examined by immunofluorescence and flow cytometri c analyses. Lymphocyte markers included fluorescence-conjugated monocl onal antibodies to identify T cells (CD3), T helper cells (CD4), cytot oxic T cells (CD8), and B cells (IgM). The proportions among blood lym phocyte 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, parti cularly at the time when most hatchmates developed SLV. Examination of leukocyte alterations with respect to first observation of SLV reveal ed that inflammatory leukocyte levels were elevated early in SLV. Alth ough 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 de struction. The role of inflammatory blood leukocytes in the developmen t of SLV needs to be further investigated.