Immunoarchitecture of Distinct Reticular Fibroblastic Domains in the White Pulp of Mouse Spleen

The development of peripheral lymphoid tissues requires a series of cognate interactions between hemopoietic and stromal cell populations, including reticular fibroblasts, which form the mesenchymal scaffolding of distinct tissue compartments. Here we describe the formation of different fibroblastic domains in the mouse spleen white pulp by using two new rat monoclonal antibodies (MAbs). In the white pulp, MAb IBL-10 labels both T- and B-cell zone reticular elements at various intensities. The IBL-10hi subset was found primarily at the edge between the peripheral part of the PALS and follicles, and the IBL-10lo compartment was distributed evenly within the white pulp. The IBL-10hi subset appeared during the first 2 postnatal weeks and was absent in SCID mice. The white pulp fibroblast subset identified with MAb IBL-11 had a different tissue distribution and kinetics of ontogeny, with an appearance overwhelmingly restricted to the PALS and a narrow rim at the edge of the follicular border area toward the marginal zone. The appearance of IBL-11-positive reticular cells was delayed compared with that of the IBL-10lo-positive subset. The formation was independent of the influence of antigen receptor-bearing lymphocytes, as evidenced by the presence of IBL-11-positive fibroblasts in SCID mice. By transferring various lymphocyte subsets into SCID mice, partial compartmentalization of the white pulp fibroblasts could be induced, indicating that these mesenchymal fibroblast precursors retain their ability to differentiate upon encountering mature T- or B-cells.