interleukin secretion trait interleukin-9 secretion trait IL9 secretion Any measurable or observable characteristic related to the controlled release of a multifunctional cytokine secreted primarily by activated TH2 cells that may play a role as a regulator of allergic inflammation, and has been shown to enhance the growth and differentiation of mast cells, and can act on a variety of other immune cells. T-Cell Growth Factor P40 secretion P40 T-Cell Growth Factor secretion IL-9 secretion VT:0008710 EFO:0802663 Trait.ontology