Depletion of enteroantigen-activated CD4⁺ T cells: effects on proliferation and pathogenicity

Naive CD4(+) T cells depleted of natural Treg (CD25(+)) cells proliferate extensively when exposed to a fecal extract [enteroantigen (eAg)] pulsed on antigen-presenting cells (APC). When transplanted into SCID recipient mice, the CD25-depleted T cells induce a chronic colitis with a lethal course. We observed here that if T cells, pre-activated for 48h by eAg from BALB/c or SCID mice, are removed and then reexposed to either of the two sources of antigen, these T cells have completely lost their anti-eAg proliferative capacity in vitro. This observation indicates that eAgs derived from Balb/c and SCID mice are recognized by similar subsets of T cells. However, when transferred into SCID mice, eAg-activation-depleted T cells are still capable of inducing a severe colitis fully comparable with the disease induced by naive CD4(+) T cells.