Detection of phenotypic heterogeneity within the murine splenic vasculature using rat monoclonal antibodies IBL-7/1 and IBL-7/22

The homing of lymphocytes into various peripheral lymphoid organs involves a complex set of interactions between the circulating lymphoid cells and th e local endothelium, While the initial binding and the adhesion processes o f lymphocytes leading to their homing to the lymph nodes have thoroughly be en studied, relatively little is known about the lymphoid-endothelial inter actions taking place in the spleen. Our aim was to isolate rat monoclonal a ntibodies (MAbs) against the endothelial cells of the mouse spleen. Using s plenic stroma derived from irradiated mice as antigen, two new rat MAbs wer e isolated. The MAb designated as IBL-7/1 bound to the sinus-lining (littor al) cells in the red pulp, marginal zone, and to the T- and B-cell compartm ents of the white pulp, respectively. However, it did not react with the ce ntral arteriole in the periarteriolar lymphoid sheath (PALS), In contrast t o this pattern, the IBL-7/22 MAb recognized a shared antigen expressed by t he sinusoidal and arterial endothelium, In addition to the endothelial reac tivity, the IBL-7/22 MAb also stained the reticular components of the PALS and red pulp, but not that of the follicles, In vivo labelling with fluores cein (FITC)-conjugated IBL-7/1 MAb followed by confocal microscopic analysi s revealed that the antigen recognized was expressed on the luminal surface of the sinusoids, The treatment of mice with IBL-7/1 MAb did not result in the altered distribution of T and B cells. These two new MAbs may be valua ble tools for the phenotypic analysis of splenic endothelium, and can be us ed for the identification of various endothelial cell subpopulations of the mouse spleen.