Skin inflammation enhances the induction of a DTH response to OVA in WT mice.

(A) Schematic representation of the experiment: WT mice were grouped into a control (CTR) group, a DAY 2 and a DAY 9 group. On day -14 and day -7, mice from the DAY 9 group or the DAY 2 group, respectively, were sensitized by application of oxazolone (OXA) onto the belly and paws (indicated as OXA-SENS). 5 days later (day -9 or day -2) a CHS response was induced, by challenging mice from the DAY 9 or DAY 2 groups with oxazolone on the right ear (indicated as OXA-CHALL). In mice belonging to the DAY 9 group, OXA was repeatedly applied onto the right ear on day -7 and day -4, to maintain the inflammatory response. On day 0, corresponding to 2 days (DAY 2 group) and 9 days (DAY 9 group) after the onset of inflammation (marked as a red bar), a DTH experiment was initiated in mice from all treatment groups. To this end, all mice were immunized by OVA injection into the CHS-inflamed or control right ear (indicated as OVA-SENS). On day 7, a DTH response to OVA was induced by OVA injection into the left ear (indicated as OVA-CHALL). The strength of the immune response in the left ear was analyzed two days later (day 9). (B) The ear swelling response in the left ear was significantly stronger when mice had been immunized by OVA injection into the inflamed, right ear. The Δ ear thickness is shown, defined as the difference between the ear thickness measured at baseline and the ear thickness measured two days after DTH induction. CFA group: As a positive control group, some untreated mice were immunized by injection of OVA plus CFA into the uninflamed right ear (R) on day 0, followed by a regular OVA challenge into the left ear (L) on day 7 (as described in 3B). (C–F) FACS analysis was performed on single-cell suspensions of the DTH-challenged, left ear to quantify leukocyte infiltration. Quantification of (C) total leukocytes (CD45⁺), (D) neutrophils (CD11b⁺Gr1⁺), (E) CD4⁺CD3⁺CD45⁺ T cells and (F) CD8⁺CD3⁺CD45⁺ T cells. (G) Quantification of OVA-specific total IgG in the serum of mice. Representative data from 1 out of 3 similar experiments (n = 6–7 mice/group) are shown. *p<0.05; **p<0.01.