IL17A and immunodeficiency disease: One possible mechanism may be related to the preferential loss of Th17 cells in the GI tract in progressive immunodeficiency lentiviral infections [25], [26], because Th17 cells produce cytokines important for enterocyte proliferation and antibacterial defensins [49], [50], [51] and IL-17 has recently been shown to suppress Th1-mediated damage to gut epithelium.