Obese strain (OS) chickens with spontaneous autoimmune thyroiditis have a deficiency in thymic nurse cells

Chicken thymic nurse cells (TNC) were isolated and their plasma membrane antigens were characterized by immunofluorescence with a panel of allo-, hetero-, and monoclonal antibodies. Analogous to the murine system, chicken TNC are localized in the subcapsular region of the cortex and were strongly B-L and B-F positive (MHC Ia and H-2 D, K equivalents). The TNC were non-phagocytic and lacked fc receptors, but expressed an antigen specific for thymic epithelial cells, and their cytoplasm was stained by an anti-keratin antiserum. The internalized lymphocytes were all intact T cells of a distinct differentiation stage, their antigenic profile consistent with that of immature cortical thymocytes. To determine whether TNC may play a role in the activation of autoimmune disease, Obese strain chickens with spontaneous autoimmune thyroiditis were investigated. These chickens were found to have a twofold defect in their TNC content: the thymuses contained approximately one-half of the number of TNC found in normal chickens beginning as early as 17 days of embryogenesis, and the lymphocyte content of the Obese strain TNC was one-half that of the normals. The deficiency is specific for TNC and may be a major reason for the abnormal T cell differentiation in the Obese strain.