Objective:Study of aprotinin effect on patients immunity system and complement during open heart operation.Methods:Ig and complement in patients' blood were measured respectively before operation and on the operative day and the first,second,third postoperative day.Results:In both aprotinin and comparative groups,the plasma levels of IgG,IgA,IgM,IgE and complement C3,C4,CH50 dropped remarkably and began to rise from the first postoperative day.On the third postoperative day, the plasma levels of IgG,IgA and complement C3,CH50 basically restored to the levels before operation.While IgM,IgE and complement C4 in aprotinin group and all Ig with complement in comparative group did not.Conclusion:Aprotinin has not a protective function to patients' immnunity system and complement during open heart operation but it can improve their restoration postoperatively.