Transplant rejection is the loss of graft function or organismal damage caused by the immune response induced by the transplant antigen. Immunological monitoring of renal transplant rejection includes: i. Body fluid immune level testing 1. ABO blood type. Liu Zhanmin, Department of Laboratory Medicine, Qinhuangdao Orthopaedic Hospital 2. Other blood types. 3. HLA antibodies: detection of anti-donor HLA antibodies uses cross-fit tests to detect the presence of anti-donor HLA antibodies in the patient’s serum, the presence of which predicts the possibility of rejection. 4. anti-donor tissue cell antibodies. 5. Antibodies to vascular endothelial cells. 6. 6. cold agglutinin antibodies. II. Peripheral T-cell count: The T-cell count of peripheral blood was determined by monoclonal antibody immunofluorescence method or flow cytometry to determine T-cells and their subpopulations. It is generally believed that when the ratio is greater than 1.2, acute rejection is imminent; when the ratio is less than 1.08, the possibility of infection is high. If dynamic monitoring can be performed, it will be of great value in the differential diagnosis of acute rejection and infection.