Within six days following A. butzleri CCUG 30485 strain infection, CD3+ cell numbers (i.e. T lymphocytes) increased by more than twofold (p<0.0005; Fig 3A), but declined back to numbers observed in naive mice until day 16 p.i. In C1 strain infected mice, however, an increase in colonic T cells of approximately 25% in gnotobiotic IL-10-/- mice could be observed until day six as well as day 16 p.i. (p<0.05 and p<0.0005, respectively; Fig 3A). Here, IL10 is linked to infection.