Study of Ravulizumab in Proliferative Lupus Nephritis (LN) or Immunoglobulin A Nephropathy (IgAN)

Inclusion Criteria: Common to both disease cohorts: * Proteinuria ≥1 (gram \[g\]/day or g/g) * Vaccinated against meningococcal infection * Vaccinated for Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae according to national/local regulatory requirements For LN cohort: * Diagnosis of active focal or diffuse proliferative LN Class III or IV * Clinically active LN, requiring/receiving immunosuppression induction treatment For IgAN cohort: * Diagnosis of primary IgAN * Compliance with stable and optimal dose of renin-angiotensin system inhibitor treatment for ≥ 3 months Exclusion Criteria: Common to both disease cohorts: * eGFR \< 30 milliliters/minute/1.73 meters squared * Previously received a complement inhibitor (for example, eculizumab) * Concomitant significant renal disease other than LN or IgAN * History of other solid organ or bone marrow transplant * Uncontrolled hypertension For IgAN cohort: * Diagnosis of rapid progressive glomerulonephritis * Prednisone or prednisone equivalent \> 20 milligram (mg) per day for \> 14 consecutive days or any other immunosuppression within 6 months