Acquired immunodeficiency syndrome (AIDS), resulting from infection with the human immunodeficiency virus (HIV), remains a major global health threat. Multiple studies have demonstrated the presence of anti-HIV IgG in the urine of HIV-positive individuals without evident renal pathology. Despite the availability of HIV urine test kits and initial investigations into the origins of anti-HIV antibodies in urine, the underlying mechanism remains inadequately defined. This paper reviews the literature on IgG production pathways within humoral and mucosal immunity, non-B lymphocytes, and relevant transport receptors, such as the neonatal Fc receptor (FcRn), aiming to provide insights into the mechanism driving antibody excretion in urine.