Immunological and Molecular Roles of Interleukin 17 Receptor A in Protective Immunity Against Giardia

Interleukin-17 receptor A (IL-17RA) plays an important role in coordinating mucosal immunity against Giardia, an intestinal protozoan parasite that colonizes the small intestine. This review examines the immunological and molecular functions of IL-17RA, emphasizing intestinal gene regulation, immunoglobulin A (IgA) transport, and downstream defense mechanisms. Particular attention is given to receptor-associated signaling, the polymeric immunoglobulin receptor, mannose-binding lectin, and antimicrobial proteins. The distinction between increased expression of defense-related genes and demonstrated antiparasitic activity is essential for interpreting these mechanisms. Host age, intestinal microbiota, epithelial function, and parallel physiological responses further influence the effectiveness of protection. Although human studies support the involvement of IL-17A-producing memory CD4⁺ T cells, most causal evidence derives from experimental animal models. IL-17RA therefore provides an important framework for understanding how cytokine signaling coordinates intestinal defense against a lumen-dwelling parasite. Further cell-specific investigations and longitudinal human studies are needed to clarify its clinical relevance and potential value in biomarker research and preventive strategies.