Cellular and molecular characterisation of the ovine rectal mucosal environment.

Immunohistological characterisation of ovine rectal tissue has revealed the presence of lymphoid follicles, predominantly in the submucosa, that closely resemble those found in intestinal Peyer's patches (PPs). Distinct T (CD4+, CD8+, gammadelta-TCR+) and B (CD21+, CD45R+) lymphocyte staining patterns were observed within and around follicles of the rectal mucosa. In addition, IgA+ and IgE+ cells were also found at this tissue site, with both phenotypes commonly residing in the lamina propria. RT-PCR examination of the cytokines expressed in the rectal mucosal tissue revealed consistently high levels of TGFbeta and IL-8 mRNA, low levels of IL-2 mRNA and no detectable IL-4 mRNA. The presence of lymphoid follicles, IgA+ plasma cells and IgA-inducing cytokines in rectal tissue of sheep indicate that this may be a suitable route for delivering mucosal vaccines.