IL17, also known as CTLA8, is a T cell derived hematopoietic cytokine. It was originally cloned from a T cell hybridoma produced by fusion of a mouse cytotoxic T cell clone and a rat T lymphoma. IL17 exhibits multiple biological activities on a variety of cells including: the induction of IL6, IL8 and GCSF production in fibroblasts; the enhancement of surface expression of ICAM 1 in fibroblasts; activation of NF kappaB and costimulation of T cell proliferation. IL17 is an approximately 16 kD