We next analysed binding of CTLA-4-Ig on DCs and B cells after sensitization with DNFB. Mice were treated with 25 mg/kg of CTLA-4-Ig or control protein 1 day prior to sensitization. As shown in Fig. S1A, significant binding of CTLA-4-Ig to DCs could be detected on day 3. Furthermore, we found a significantly reduced expression of CD86 4 and 5 days after sensitization in CTLA-4-Ig-treated mice (Fig. S1B,C). In contrast, no specific binding of CTLA-4-Ig to B cells could be detected at either time-point examined (Fig. S1D), but expression of CD86 on B cells was strongly suppressed at every time-point after sensitization in the CTLA-4-Ig-treated group compared to treatment with isotype control

(Fig. S1E,F). Together, these data suggest that CTLA-4-Ig binds p38 MAPK cancer preferentially to DCs in the draining lymph node after hapten

sensitization, and that CTLA-4-Ig reduces the level of the maturation marker CD86 on both DCs and B cells. Having demonstrated a reduction of CD4+ and CD8+ T cell activation in draining lymph nodes in the presence of CTLA-4-Ig, we wanted to investigate the consequences for the inflammatory reaction in the tissue after challenge. Thus, infiltrating cells were isolated from the inflamed ear 48 h after challenge, stained for activation markers and analysed by flow cytometry. As shown in Fig. 4, CTLA-4-Ig treatment led to a significant reduction in both number and percentage of CD8+ T cells in the inflamed ear compared to controls (Fig. 4a). In contrast, the Cell Cycle inhibitor number of CD4+ T cells was not significantly different, but the percentage of CD4+ T cells was increased in the CTLA-4-Ig-treated group (Fig. 4b). More importantly, CTLA-4-Ig treatment resulted in a reduction in the number of Janus kinase (JAK) activated CD8+ T cells in the inflamed ear

compared to controls. Thus, we observed a decreased number and percentage of CD44+CD62L−CD8+ T cells and CD69+CD8+ T cells in the CTLA-4-Ig-treated group compared to controls (Fig. 4c,d). In conclusion, these results suggest that CTLA-4-Ig inhibits infiltration of activated CD8+ T cells into the challenged tissue. To correlate the reduced cellular infiltration into the target tissue after CTLA-4-Ig treatment with the local production of cytokines and chemokines, homogenates of inflamed ear tissue from CTLA-4-Ig-treated and isotype control-treated animals were analysed for their content of a number of cytokines and chemokines including IL-4, CXCL10 (IP-10), IL-12 (p40), MIP-2, TNF-α, IFN-γ, IL-1β, IL-10 and IL-6. As shown in Fig. 5, IL-1β and IL-4 were suppressed significantly in the CTLA-4-Ig-treated group compared to the control group both in the DNFB- and in the oxazolone-induced models (Fig. 5a–d). Additionally, the concentrations of the chemokines MIP-2 and CXCL10 (IP-10) were reduced in both models (Fig. 5c,d,g,h) after CTLA-4-Ig treatment.