heilmannii-infected WT mice (Fig. 2a lower right and

2b). Lymphoid follicles were observed dominantly at the corpus of both H. heilmannii-infected WT and PP null mice, and gastritis, which is characterized by the diffuse pattern of infiltration of inflammatory cells and atrophy of mucosa, was not found in both H. heilmannii-infected WT and PP null mice at 1 and 3 months (Fig. 2a). These results suggest that PP are not essential for the induction of gastric lymphoid follicles by H. heilmannii infection, although they are involved in the speed of gastric lymphoid follicle formation. PP are the major induction sites of immune responses to microorganisms and pathogens in the gastrointestinal Talazoparib manufacturer LDK378 tract (Newberry & Lorenz, 2005). To examine which kinds of inflammatory cells were present in the gastric mucosa of WT and PP null mice infected with H. heilmannii, an immunohistological examination was carried

out using anti-B220, CD11c, and CD4 antibodies (Fig. 3a and b). In the WT mice 1 month after H. heilmannii infection, many B220-positive cells; i.e. B cells, were observed (Fig. 3a middle left). Most of them clustered together, mainly at the lamina propria of the gastric mucosa, and B cells seemed to be the main components of lymphoid follicles. Many CD11c-positive cells; i.e. dendritic cells (DC), and CD4-positive cells; i.e. helper T cells, were also 4-Aminobutyrate aminotransferase detected in the lymphoid

follicles and the surrounding sites (Fig. 3a and b middle left). On the contrary, the spread pattern of these infiltrated cells was relatively mild. In the WT mice 3 months after H. heilmannii infection, more B cells and helper T cells gathered and formed larger lymphoid follicles (Fig. 3a and b middle right). In the PP null mice 1 month after H. heilmannii infection, some cell clusters containing B cells, DC, and helper T cells were observed, and the location of these cells and their proportion in and around cell clusters were similar to those of WT mice (Fig. 3a and b lower left). However, the number of these cell clusters, which is considered as a more sensitive and accurate severity index of the cell infiltration than its number determined by H&E staining, was significantly lower in the PP null mice than in the WT mice (Fig. 3c). Three months after infection, similar results were observed between the H. heilmannii-infected WT mice and PP null mice (Fig. 3a,b, Fig 3c lower right). From these results, it was suggested that H. heilmannii infection causes the infiltration of DC, B cells, and helper T cells into the gastric mucosa and that they are the main components of the lymphoid follicles formed by H. heilmannii infection. In addition, these results indicate that the mucosal immune responses triggered at H. heilmannii infection sites are not completely inhibited even in the absence of PP.