IL17A and inclusion conjunctivitis: We used our standard in vitro collagen gel contraction assay9, 10 to determine the contractile profile of STFs and CFs, in the presence of serum (10%) or cytokines and growth factors previously linked to active and scarring trachoma (PDGF-BB, TGF-b1, IL-1b, IL-17A, TNFα, CTGF, CXCL5)2, 8.