Interleukin-17 is a cytokine that belongs to a family of six members (interleukins 17A through 17F), which bind a total of five receptors (interleukins 17RA through 17RE).¹–³ Of these six interleukin-17 cytokines, interleukins 17A and 17F are very homologous and bind the same receptor complex (interleukins 17RA and 17RC). Interleukin-17A is the founding member of the family and is therefore also termed interleukin-17.⁴ It was identified in 1993 as a cytokine that mediates the production of chemokines and subsequently the recruitment of neutrophils to sites of inflammation.³ Although interleukin-17 has been discussed recently with reference to autoimmune diseases, one . . .