Developmental profile of select immune cells in mice infected with Trichinella spiralis during the intestinal phase

- Stimulation index of T cells decreased significantly from 7 to 11 dpi, and CD4+/CD8+ ratio was lowest at 7 dpi.
- The number of B cells was increased over the entire intestinal phase except on 7 dpi.
- The expression of CD14 on monocyte-macrophages was decreased before 15 dpi, and T. spiralis invasion can induce peritoneal macrophages to M2 during the intestinal phase.

Trichinella spiralis can cause immunosuppression during the intestinal phase of early infection. However, changes in the peripheral blood during T. spiralis early infection remain unclear. Here, select immune cells in mice infected with 500 muscle larvae (ML) of T. spiralis during the intestinal phase of infection were studied. First, the recovery rates of the intestinal worms and female fecundity were determined, and the results showed that the intestinal worms were completely eliminated at 17 days post-infection (dpi) and that large numbers of new-born larvae (NBL) were generated from 5 to 9 dpi. Using flow cytometry, it was shown that the number of CD4+ T cells and CD8+ T cells increased over the entire intestinal phase, except on 7 dpi when CD4+ T cells decreased significantly compared to the control groups. Although both CD4+ and CD8+ T cells increased, CD8+ T cells increased more than CD4+ T cells, leading to a lower CD4+/CD8+ ratio compared to the control group. Subsequently, a depression of the proliferative response of T cells to concanavalin A (Con A) was noticed at 7 and 11 dpi. Although the proliferative response of B cells to LPS was enhanced, the number of B cells from mouse peripheral blood stimulated by T. spiralis antigens showed no differences with the control group prior to 11 dpi. The expression of CD14 on monocyte-macrophages decreased during the same period, which meant that the antigen-presenting response was reduced in the immune system of the infected mice. Moreover, the alternatively activated macrophages were induced in T. spiralis early infection. These data provide a better understanding of the development of the intestinal immune response in mice infected with T. spiralis.