Fig 2: Gene expression in the skin, and Ab production in Il17c−/− mice. (a) Relative mRNA expression levels of cytokines and chemokines in the ear skin of wild-type and Il17c−/− mice 24 hours after FITC challenge. V = vehicle treatment. Wild-type mice (vehicle, n = 3; FITC, n = 5) and Il17c−/− mice (vehicle, n = 3; FITC, n = 6). (b) Relative mRNA expression levels of cytokines and chemokines in the ear skin of wild-type and Il17c−/− mice 24 hours after DNFB challenge. V = vehicle treatment. Wild-type mice (vehicle, n = 3; FITC, n = 5) and Il17c−/− mice (vehicle, n = 3; FITC, n = 5). (c) Sera were collected from mice 72 hours after FITC challenge. The levels of FITC-specific Ig subsets in sera were determined by ELISA. N = naïve. Wild-type mice (naive, n = 8; FITC, n = 30) and Il17c−/− mice (naive, n = 4; FITC, n = 32). (d) Sera were collected from mice 72 hours after DNFB challenge. The levels of DNP-specific Ig subsets in sera were determined by ELISA. N = naïve. Wild-type mice (naive, n = 8; DNFB, n = 27) and Il17c−/− mice (naive, n = 5; DNFB, n = 30). The data show the mean + SEM. *p < 0.05, **p < 0.01 and ***p < 0.001: vehicle vs FITC or DNFB; and †p < 0.05 and ††p < 0.01: wild-type mice vs. Il17c−/− mice. Analyses by Mann-Whitney U-test, two-tailed (a, b) and Student’s t-test, two-tailed (c, d). NS = not significant.

Fig 3: Normal development of T cell-independent pulmonary fibrosis in Il17c-/- mice. Male mice were treated intratracheally with bleomycin (BLM) or PBS. 14 days later, bronchoalveolar lavage (BAL) fluids and the lungs were collected. (a) Cell counts in BAL fluids. Wild-type mice (PBS, n = 5; BLM, n = 9) and Il17c-/- mice (PBS, n = 5; BLM, n = 7). The data show the mean + SEM. **p < 0.01 and ***p < 0.001: PBS vs BLM; and †p < 0.05: wild-type mice vs. Il17c-/- mice. (b,c) Representative images of lung sections. Hematoxylin and eosin staining (b) and Elastica van Gieson staining (c). Bars = 100 µm.

Fig 4: High susceptibility of Il17c-/- mice to T cell-independent DSS-induced colitis. Female mice were provided sterile drinking water containing 2.0% DSS ad libitum for 5 days, followed by 15 days of regular drinking water. (a) Change in body weight (%). Wild-type mice (n = 10) and Il17c-/- mice (n = 10). *p < 0.05 and **p < 0.01 vs. corresponding values for Il17c-/- mice. (b) Area under the curve (AUC) for the body weight on Days 5–8 in (a). **p < 0.01. (c)Representative pictures of the animals’ colons on Day 8. (d) Length of colons on the indicated days. Wild-type mice (naïve, n = 4; and Days 8, 15, and 33, n = 4–5) and Il17c-/- mice (naïve, n = 4; and Days 8, 15, and 33, n = 8–10). (e) Representative images of colon sections (Day 8) stained with hematoxylin and eosin. Bars = 100 µm. (f) Histological scores on Day 8. **p < 0.01. The data show the mean + SEM (a,b,d,f).

Fig 5: Generation of Il17c-/- mice. (a) IL-17C gene targeting strategy. The region of the Il17c gene containing from exon 1 to exon 3 was replaced with a cassette containing a neomycin resistance gene (Neor), flanked by loxP sequences. (b) Expression of Il17c mRNA in various tissues from wild-type (n = 3) and Il17c-/- (n = 3) mice, determined by qPCR. The data show the mean + SEM.