C3a/C3aR Affects the Propagation of in the Ileum Tissues of Mice by Regulating the Gut Barrier, Cell Proliferation, and CD4 T Cell Main Effectors.

is an important zoonotic protozoon that threatens the health of humans and animals, but the interaction mechanisms between and hosts are poorly understood. Our previous study indicated that the expression levels of C3a and C3aR were up-regulated in mice during infection, but the mechanisms of C3a/C3aR signaling during infection have not been elucidated. In the present study, an optimized BALB/c suckling mouse model infected with was used to explore the function of C3a/C3aR signaling during infection. The expression levels of C3aR in the ileum tissues of mice infected with were analyzed using real-time PCR, Western blot and immunohistochemistry. The mRNA levels of the gene, tight junction proteins (, , and ), intestinal stem cell marker , cell proliferation marker , Th1 cell-related cytokine , and Treg cell-related cytokine in mouse ileum tissues were analyzed by real-time PCR. The pathological injury of ileal mucosa was examined by histopathology analysis. The mRNA expression levels of gene were significantly up-regulated in the ileum tissues of C3aR-inhibited mice during infection. Meanwhile, histopathology analysis of ileal mucosa in mice showed that inhibition of C3aR significantly aggravated the changes in villus length, villus diameter, mucosal thickness and the ratio of villus length to crypt depth during infection. Further studies found inhibition of C3aR aggravated the down-regulation of at most time points during infection. The mRNA levels of and in the ileum tissues of mice infected with were significantly down-regulated. Inhibition of C3aR significantly down-regulated the mRNA expression levels of at most time points, but significantly up-regulated the mRNA expression levels of at most time points. The mRNA expression levels of and were significantly up-regulated and down-regulated in the ileum tissues of mice infected with , respectively. However, inhibition of C3aR significantly increased the mRNA expression levels of and in the ileum tissues of mice infected with . Taken together, C3a/C3aR signaling could possibly affect the propagation of in mouse ileum tissues by regulating the gut barrier, cell proliferation and CD4 T cell main effectors, which would contribute to our understanding of the interaction between and hosts.