Ancient interleukins 2, 15, and 15-like exhibited distinct functions but all bound IL-15Ra

(Fujita Health University) Interleukin-15-like (IL-15L) is found in both fish and mammals and may be the last remaining cytokine shared between those species for which the function had not been determined yet. Scientists now report the first functional analysis of cytokine IL-15L which, similar to related IL-15 and primitive IL-2, forms a complex with receptor chain IL-15Ra, but in contrast to these cytokines selectively induces a type 2 immune response.