NCIt definition : A subset of helper T-lymphocytes which synthesize and secrete the interleukins (IL),
IL-17A, -21 and -22. These cytokines mediate inflammation by increasing chemokine
production, which leads to the recruitment of both monocytes and neutrophils to sites
of infection or inflammation. Th17 cells modulate both host immunity against extracellular
bacteria and fungi and inflammation. Overexpression of these cells is associated with
tissue injury caused by autoimmune diseases.;