4c). While anti-CD3-stimulated IL-10 secretion was at the same magnitude as bacterial antigen-stimulated secretion, the release of IFN-γ was between 16-fold (day 7) and 30-fold (day 0) higher for anti-CD3 stimulation compared selleckchem to bacterial stimulation, suggesting that the potential repertoire of IFN-γ-producing T cells was higher than the repertoire stimulated by bacterial antigens alone. In contrast, the stimulation of IL-10 secreting T cells was linked tightly to bacterial antigen stimulation. It is possible that some of the cytokine production could also be a result of activation of other monocytic spleen cells via their Toll-like-receptors or through

a downstream bystander effect. To test for a possible regulatory mechanism for the decline in cytokine production after day 7 post-injection, we examined the amount and composition Selleckchem LBH589 of a variety of cells within the spleen cell population. No significant change in the percentage of CD25-positive cells was detected (Fig. 5a), suggesting that regulatory T cells within this population were not instrumental in the down-regulation of the immune response. However, concomitant with the increase of cytokine release at day 7 we found an increase in the number of CD11b-positive

leucocytes (Fig. 5b). An overlap of CD11b staining with markers for T cells (anti-CD3), B cells (B220) and dendritic cells (anti-CD11c) was less than 2%, while on average more than 68% of these cells also stained for Gr-1, suggesting

a myeloid-derived suppressor cell phenotype (data not shown). There was no significant change in total number of spleen cells recovered from mice at the various time-points post-faecal ingestion (Fig. 5c). Similarly, changes in numbers and percentages of both CD3-positive T cells and B220-positive B cells were not significant. However, the ratio of B220/CD3-positive cells was reduced significantly from 1·54 ± 0·14 (day 0) to 1·02 ± 0·03 (day 14) as a consequence of a slight increase in percentage of T cells and a concomitant decrease in the percentage of the B cell population at days 7–14. In this study we have Flavopiridol (Alvocidib) investigated the impact of commensal faecal flora and antigen acquisition in an immune environment that developed in the absence of an enteric bacterial influence. Generally the mammalian gastrointestinal tract is populated with a highly diverse microbial flora immediately after birth. Studies employing gnotobiotic rodent colonies have shown that microbial colonization affects the general morphology, gut motility and differentiation of epithelial cell lineages [10–12]. In addition, acquisition of intestinal microflora is vital for the development of immunity. Gene expression profiling has revealed that the residential microbiota modifies genes significantly, including those involved in immune function [13,14]. Expression of several activation markers on intestinal immune cells is greatly reduced in axenic mice [11].