Figure 5. Histopathology of mesenteric lymph nodes and intestinal lamina propria.

(A) S1PL^+/+ lymph node: Paracortical zones are filled primarily with lymphocytes (B) S1PL^−/− lymph node: Small B cell lymphoid follicles appear as small semicircular caps overlying an expanded but relatively hypocellular paracortical zones. At higher magnification (lower panel), the paracortex contains markedly increased numbers of granulocytes and macrophages (some vacuolated and containing karyorrhectic debris), mixed with stromal cells and plasma cells. (C) S1PL^H/H lymph node: There is marked expansion of paracortical zones. At higher expansion, this expansion is due primarily to sequestered lymphocytes. (D) S1PL^H/− lymph node: Similarly, the marked expansion of paracortical zones is due primarily to sequestered lymphocytes (lower panel). (E) S1PL^+/+ lamina propria: Lymphocytes and plasma cells predominate in the lamina propria of Wt mice. (F) S1PL^−/− lamina propria: There is a marked depletion of lymphocytes and plasma cells and increased numbers of granulocytes (arrows) in the intestinal lamina propria. (G) S1PL^H/H lamina propria: Essentially normal cell populations are present. (H) S1PL^H/− lamina propria: Essentially normal cell populations are present. H&E stain.