Currently, the treatment options of recurrent IgA nephropathy (IgAN) are conflicting and largely based on expert opinions. Consequently, the recent KDIGO clinical practice guideline for the care of kidney transplant recipients has concluded that there are no definite strategies for prevention and treatment. However, recurrent IgAN in the transplanted kidney is common and may contribute to graft loss, in particular, if cresentic formation, extra- or endocapillary proliferation were presented in kidney pathology. Herein, the investigators assume that rituximab, anti-CD20 Ab agent, can reduce circulating IgA with subsequently decrease rate of polymeric forms of IgA deposition in glomerular capillaries. Therefore, the investigators speculate that rituximab may have potential effect to reduce circulating polymeric forms of IgA and slow progression of recurrent IgAN.

Hypothesis: In kidney transplant recipients with active endocapillary proliferation pathology of recurrent IgAN, an intravenous infusion of 375mg/m2 of rituximab on 4 consecutive monthly dose is superior to conventional therapy in reducing 24-hour proteinuria, and slowing progression of recurrent IgAN.

Inclusion Criteria:

• Any kidney transplant recipients between the age of 18 and 70 years of age and able to give informed consent
• GFR by 24h Creatinine Clearance (CrCl) >30 ml/min/1.73m²
• Biopsy proven recurrent IgA nephropathy with endocapillary proliferation pattern

Exclusion Criteria:

• Clinical and histologic evidence of IgA combination with other forms of glomerulonephritis
• Clinical evidence of cirrhosis, chronic active liver disease or known infection with hepatitis B, C or HIV
• 24h CrCl <30 ml/min/1.73m² at the time of screening
• Active systemic infection or history of serious infection within one month of entry
• Positive pregnancy test or breast feeding at time of study entry
• Patients receiving >6 months therapy with oral prednisone >5mg/day or glucocorticoid equivalent
• Live vaccine within 28 days of study enrollment.