n :  any of various substances (as an interleukin) of low molecular weight that are not antibodies, are secreted by T cells in response to stimulation by antigens, and have a role (as the activation of macrophages or the enhancement or inhibition of antibody production) in cell-mediated immunity .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.