Monoclonal antibodies against mouse splenic stromal cells.

A panel of rat monoclonal antibodies directed against mouse splenic stromal cells were isolated. These monoclonal antibodies were Immunohistochemically divided into four groups which reacted with non-lymphoid cells of the murine spleen; (1) in the white pulp, (11) at the marginal zone, (111) in the red pulp, and (IV) on the endothelium of splenic blood vessels. These monoclonal antibodies were studied Immunohistochemically In lymphoid organs by means of light and electron microscopy. Monoclonal antibodies SS-4 (group I) reacted with fibroblastic reticulum cells that were distributed only in the white pulp of the spleen and In the follicular areas of lymph nodes. The SS-4 staining cell, In clustered splenic stromal cells, formed colonies which Included a small number of Thy-1 positive lymphocytes. Therefore, we concluded that SS4 staining stromal cells comprise the lymphoid cornpartment. In contrast, monoclonal antibodies SS-1, SS-3 and SS-5 (group II) reacted with dendritic shaped cells in the marginal zone of the spleen. Examination of splenic extra-medullary hematopolesis in mice rescued by bone marrow transplantation after lethal irradiation revealed that SS-3 and SS-5 reacted with dendritic shaped stromal cells in clonal nodules of engrafted marrow in the red pulp. SS-3 and SS-5 staining cells could not be observed in physiologic hematopoiesis of non-transplanted mice. It was suggested that SS3 and SS-5 staining stromal cells are Involved in primitive hematopoiesls. Monoclonal antibodies SS2, SS-6 and SS-7 (group 111) mainly reacted with dendritic cells and macro-phages in the red pulp. Monoclonal antibodies SS-8 and SS-9 (group IV) reacted with endothelial cells of blood vessels and sinuses. These findings of heterogeneity in mouse splenic stromal cells are further evidence that specific micro-envlronments are composed by speclalired stromal cells.