Involvement of 4-1BB (CD137)-4-1BBligand interaction in the modulation of CD4 T cell-mediated inflammatory colitis

Abstract

4-1BB ligand (4-1BBL) expressed on antigen-presenting cells interacts with 4-1BB on activated T cells (especially CD8+ cells) and co-stimulates the latter to secrete cytokines and to proliferate. The role of 4-1BB-4-1BBL interaction was studied here in a model of colitis based on naive CD4+ T cell transfer to SCID mice, a disease model in which CD8 cells do not take part. We found that CD4+ T cells from 4-1BB-deficient mice, after transfer in SCID mice, proliferated more rapidly compared to wild-type CD4+ T cells. Mice reconstituted with naive CD4+ T cells from 4-1BB-deficient mice developed colitis, however, with a mixed Th1/Th2 response, in contrast to the Th1-type response in mice reconstituted with wild-type naive CD4+ T cells. Importantly, this altered cytokine response did not temper colitis severity. Although it has been reported previously that 4-1BB co-stimulation may contribute to regulatory T cell functioning, we found that CD4+CD25+ regulatory T cells from 4-1BB-deficient mice were perfectly able to prevent naive CD4+ T cell-induced colitis. In conclusion, our data provide evidence that 4-1BB-4-1BBL interaction modulates the effector CD4+ T cell-driven immune response and cytokine production in experimental colitis without affecting regulatory T cell function.

Fig. 1

In vivo homeostatic CD4⁺ T cell proliferation in the peritoneal cavity after transfer to SCID mice. CD4⁺ T cells were isolated from spleen cells of wild-type and 4-1BB^–/– mice and stained with the cytoplasmic dye carboxyfluorescein succinimidyl ester (CFSE). (a) Unstained and CFSE-stained CD4⁺ T cells from 4-1BB^–/– mice (left) and wild-type mice (right) as a negative and positive control, respectively. CFSE-stained cells were then injected intraperitoneally (i.p.) into SCID mice. At day 5, T cells were recovered from the peritoneal cavity and CFSE expression was analysed by flow cytofluorometry. (b) Representative FACS plots are shown; (c) summary bar graph representing the mean percentage plus s.e.m. of cells in the M1 and M2 area are shown (five mice per group). M1: cells which have undergone no or only few cell divisions; M2: cells which have undergo repeated cell divisions.

Fig. 2

4-1BB expression in colon and mesenteric lymph nodes of wild-type CD45RB^hiCD4⁺ T cell-reconstituted SCID mice. Microphotographs of cryostat sections of colons (a) and mesenteric lymph nodes (b) from wild-type CD45RB^hiCD4⁺ T cell-reconstituted mice were stained with anti-mouse 4-1BB monoclonal antibodies (mAb) and peroxidase-labelled rabbit anti-rat and swine anti-rabbit Ig. (c) Microphotograph of a cryostat section of colon of a 4-1BB-deficient CD45RB^hiCD4⁺ T cell-reconstituted SCID mice and stained as in (a) and (b). (d) Microphotograph of a cryostat section of colon from wild-type CD45RB^hiCD4⁺ T cell-reconstituted SCID mice stained in the presence of a control primary antibody (original magnification × 400).

Fig. 3

Comparison of disease activity after transfer of CD45RB^hi and CD45RB^lo CD4⁺ T cells from wild-type or 4-1BB^–/– mice to SCID recipients. SCID mice were reconstituted with either wild-type or 4-1BB^–/– CD45RB^hiCD4⁺ T cells, or with wild-type CD45RB^hiCD4⁺ T cells plus wild-type or 4-1BB^–/– CD45RB^loCD4⁺ T cells as indicated. Data from two independent experiments were pooled. (a) The change of weight over the observation time is expressed as a percentage of the original weight at the start of the experiment. Data represent the mean ± s.e.m. (b) Histological scores of colonic sections. Data represent the individual score for each mouse. ***P < 0·001. (a) ♦, CD45RB^hi + 4-1BB^+/+ CD45RB^lo T cells (n = 7); ▿, CD45RB^hi + 4-1BB^-/- CD45RB^lo T cells (n = 7); ▴, 4-1BB^+/+ CD45RB^hi T cells (n = 17); □, 4-1BB^-/- CD45RB^hi T cells (n = 18). (b) □, 4-1BB^-/- CD45RB^hi T cells (n = 18); ▴, 4-1BB^+/+ CD45RB^hi T cells (n = 17); ▿, CD45RB^hi + 4-1BB^-/- CD45RB^lo T cells (n = 7); ♦, CD45RB^hi+ + 4-1BB^+/+ CD45RB^lo T cells (n = 7).