ObjectiveTo observe the efficacy and safety of passive immunotherapy for treatment of renal transplant patients with severe pneumonia. MethodsFrom August 2007 to October 2009, 51 patients with severe pneumonia following renal transplantation were treated with passive immunotherapy(thymosin and immunoglobulin), and they were taken as passive immunization group; and the other 52 patients with severe pneumonia following renal transplantation from January 2005 to July 2007 were taken as control group. The basic immunosuppressant was stopped and de-escalation therapy and broad-spectrum anti-infection therapy were given to both groups. Passive immunization group was given thymosin and immunoglobulin according to the patient condition. The peripheral CD4+ T-cell counts, clinical symptoms, signs and chest CT changes were observed in both groups. ResultsThe survival rate of passive immunization group was significantly higher than that of control group (92.2% vs 75.0%, P<0.05).The time of infection control in passive immunization group was significantly shorter than that of control group (\[12.8±2.7\] d vs \[17.7±4.2\] d, P<0.05). The length of hospital stay of the survivors was significantly shorter in passive immunization group than in the control group (\[27.3±7.0\] d vs \[36.3±9.1\] d,P<0.05). No acute rejection occurred in the passive immunization group, and 4 occurred in the control group. The CD4+ T-cell counts had an increasing tendency in the survivors of both groups and had a declining trend in those who finally died. ConclusionPassive immunotherapy with thymosin and immunoglobulin can improve the survival rate of renal transplant patients with severe pneumonia, and monitoring the variation of CD4+ T-cell counts may play an important role in guiding treatment and predicting prognosis.