Chronic experimental colitis induced by dextran sulphate sodium (DSS) is characterized by Th1 and Th2 cytokines

Abstract

Oral administration of DSS has been reported to induce an acute and chronic colitis in mice. The aim of our study was to evaluate if the chronic phase of DSS-induced colitis was characterized by a Th1/Th2 response and how this would relate to mucosal regeneration. Swiss Webster mice were fed 5% DSS in their drinking water for 7 days, followed by 2-5 weeks consumption of water. Control mice received only water. The animals were killed at 3 and 6 weeks after induction. Their colons were isolated for histology and immunohistochemistry, using specific MoAbs for T and B cells, macrophages, interferon-gamma (IFN-gamma), IL-4 and IL-5. Colons were scored for inflammation, damage and regeneration. Two weeks after stopping DSS the colonic epithelium had only partially healed. Total colitis scores were still increased, especially in the distal colon, which was due to more inflammation, damage and less regeneration. In areas of incomplete colonic healing the basal parts of the lamina propria contained macrophages and CD4+ T cells. These CD4+ T cells showed a focal increase of IFN-gamma and IL-4 staining compared with control animals. These findings were still observed 5 weeks after stopping DSS in some mice, albeit less extensive. Chronic DSS-induced colitis is characterized by focal epithelial regeneration and a Th1 as well as Th2 cytokine profile. We postulate that chronic immune activation mediated by both populations of Th cells can interfere with colonic healing and can play a role in the pathogenesis of chronic colitis.

Fig. 1

Histological grading of colitis. (a) Sum of the scores of b, c, and d. (b) Inflammation score. (c) Extent of inflammation. (d) Crypt damage/regeneration score, as indicated in Table 1. Hatched bars represent mice at day 7 of DSS feeding, cross-hatched bars represent mice killed 14 days after stopping DSS, open bars depict mice 35 days after stopping DSS.

Fig. 2

(A) DSS 7 days. Multiple MOMA-2⁺ macrophages in submocosal oedema. (B) Two weeks after stopping DSS, the submucosa still contains some MOMA-2⁺ macrophages. Large lymphoid aggregates in the lamina propria, consisting mainly of B cells (C), but also T cells in the periphery (D), are shown. (E) Two weeks after stopping DSS, below an incompletely regenerated epithelium the base of the lamina propria contains bands of MT4⁺ cells.

Fig. 3

Colonic tissue 2 weeks after stopping DSS (same area as in Fig. 2E). (A) IFN-γ-producing cells (arrows). (B) IL-5-producing cells are not present. (C) IL-4-producing cells at the base of the lamina propria.

Fig. 4

IFN-γ production in organ cultures from colons of indicated time points during DSS-induced colitis and control animals; solid bars represent healthy animals, hatched bars represent mice at day 7 of DSS feeding, cross-hatched bars represent mice at day 14 after stopping DSS. *Significantly different compared with healthy animals, P < 0.05.

Fig. 5

Number of IFN-γ-, IL-5- and IL-4-positive cells in 5–10 representative areas per spleen section, expressed as number of cells/mm²; solid bars represent healthy animals, hatched bars show mice at day 7 of DSS feeding, cross-hatched bars represent mice at day 14 after stopping DSS, open bars indicate mice at day 35 after stopping DSS. *Significantly different compared with healthy controls, P < 0.05.