This study is a single-arm, single-center, open-label, dose-escalation exploratory clinical study designed to evaluate the safety, tolerability, and preliminary efficacy of CD19 CAR-γδ T cells. The subjects enrolled in this study are patients with relapsed/refractory autoimmune nephropathy, including lupus nephritis, IgA nephropathy, and membranous nephropathy. This study adopts a standard "3+3" design to assess the recommended dose (RD) and identify dose-limiting toxicities (DLTs). The treatment process is as follows: subjects who meet the inclusion criteria will receive lymphodepletion conditioning, followed by a single intravenous infusion of CD19 CAR-γδ T cells. The primary objective of this study is to evaluate the safety profile of this cellular therapy, including the incidence of DLTs, maximum tolerated dose (MTD) or RD, as well as the incidence and severity of treatment-related adverse events and clinically significant abnormal laboratory test results after CAR-γδ T cell infusion (including the incidence of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS)). The planned follow-up duration of this study is 1 years.