title: Identification of the bone marrow-derived ia positive cells in the rat thymus: a morphological and cytochemical study.
abstract: Ia+ cells of bone marrow origin were studied in the thymus of normal and bone marrow-reconstituted radiation chimeras of rats and characterized on morphology and acid phosphatase (APh)- and Ia-staining pattern in-vivo and in-vitro. In-vivo, the majority of the bone marrow-derived Ia+ cells were present in the medulla. They were large, had cell processes extending between surrounding thymocytes, and frequently weak APh activity. In-vitro, the Ia staining was demonstrated on the cell surface in variable intensity. Ia+ cells showed a frayed outline with cell processes between adherent thymocytes and had weak cytoplasmic APh activity, frequently in a central spot. They had an elongated, usually invaginated, nucleus and a rather pale cytoplasm, in which Birbeck granules sometimes were observed. The characteristics of the bone marrow-derived Ia+ cells demonstrate these cells are an equivalent of the interdigitating cells present in thymus medulla. They distinguish themselves from a population of Ia-, strongly APh+ macrophages predominantly localized in the cortex, and from the Ia+, APh- thymic reticular epithelial cells.
mesh_terms: D000135:Acid Phosphatase; D000818:Animals; D000911:Antibodies, Monoclonal; D001854:Bone Marrow Cells; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006651:Histocytochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D013194:Staining and Labeling; D013950:Thymus Gland / Q000166:cytology*
chemical_list: D000911:Antibodies, Monoclonal; D000949:Histocompatibility Antigens Class II; D000135:Acid Phosphatase