Study of PD-1Ab21-BCMA CAR-T Therapy for Consolidation of Multiple Myelomawith Renal Dysfunction

Inclusion Criteria: 1. Age: Over 14 years old 2. Diagnosed with multiple myeloma accompanied by renal dysfunction, received ≥ 2 courses of clinical first-line treatment, evaluated efficacy above PR, and predicted survival of more than three months. 3. The hospital examination meets the following indicators: 1. ECOG physical status score 0-2 or KPS score\>80 points 2. Having sufficient venous access for single or intravenous blood collection, and no other blood cells Separation contraindications 3. WBC≥1×109/L，LY≥0.3×109/L， 4. ALT and AST ≤ 2.5 ULN 5. Serum total bilirubin ≤ 2.0mg/dL (34.2 μmol/L) 6. PT:INR\<1.7 or PT prolonged by\<4s compared to normal value Exclusion Criteria: 1. Pregnant or lactating women (the safety of this treatment for unborn babies is unknown, and the assessment of pregnancy status for female participants is negative in serum or urine pregnancy tests within 48 hours prior to infusion); 2. Any uncontrollable active infection; 3. Presence of active hepatitis B or C virus infection; 4. HIV/AIDS infection; 5. Has neurological disorders; 6. Within 2 weeks prior to signing the informed consent form, systemic use of steroid drugs (inhalable steroids may be used); 7. Allergies to immunotherapy and related drugs; 8. Currently, there are patients with heart disease or poorly controlled hypertension who require treatment; 9. Currently, patients with unstable or active ulcers or gastrointestinal bleeding; 10. Patients with a history of organ transplantation or waiting for organ transplantation; 11. Hyponatremia, blood sodium\<125mmol/L; 12. Baseline blood potassium\<3.5mmol/L (potassium can be supplemented before participating in the study to restore blood potassium levels above this level); 13. The patient needs anticoagulant therapy (such as warfarin or heparin); 14. The patient requires long-term antiplatelet therapy (aspirin, dose\>300mg/d); Clopidogrel, dose\>75mg/d). Additionally, 1. Patients currently participating in other clinical trials; 2. Researchers believe that other reasons are not suitable for clinical trial participants.