Fig. 1

Procedure Test procedure illustrated in course of time. The horses were left to acclimatise for at least three days. At t-24, the horses were injected with PBS (grey symbols) i.m. (0.5 ml) and i.d. (2 × 0.5 ml). Baseline samples (blood) as internal controls for systemic parameters were acquired from t-48 – t0. At t0, horses were injected with treatments A – D (purple symbols) i.m. (0.5 ml) and i.d. (0.5 ml) and contralaterally with PBS (grey symbol, 0.5 ml). From t6 – t72, post-treatment samples (blood) of systemic parameters were acquired. At t24, skin biopsies were acquired of treatment (purple) and PBS control (grey) sites. Eleven days post-treatment (t264), one long-term sample was acquired at the home stable of each horse. General examinations were performed at all sampling times. Blood samples were used to determine WBC, haemograms, SAA, cytokine mRNA and ex vivo cytokine secretion by PBMC. Skin samples were used to perform histological examinations, IHC of IL-12, IL-18 and calprotectin, and qPCR of cytokine and chemokine mRNA