[Anti-HLA antibodies in nephropathic patients]

The presence of anti-human leukocyte antigen (HLA) alloantibodies in nephropathic patients is due to immunogenic stimuli such as transfusions, pregnancies, and transplantations. These stimuli can be highlighted using a classic aspecific serologic technique, such as complement-dependent cytotoxicity (CDC) or using more recent and specific techniques, such as cytofluorimetrics or enzyme linked immunoabsorbant assay (ELISA). Because the presence of anti-HLA preformed antibodies is linked to the largest incidence of both acute and chronic rejection, it seems appropriate to re-evaluate that data obtained using aspecific classic serological analysis techniques by using the more specific cytofluorimetric technique. To aid in the possible prevention of ant-HLA antibody formation, it is also appropriate to analyze the influence of immunogenic stimuli on the development of these antibodies.

We studied 116 patients (37 women and 79 men). Anti-HLA antibodies were detected using microlymphotoxic technique after separation of B and T lymphocytes. This separation was obtained using magnetic balls. We used a 30-cell panel. We also used a recent cytofluorimetric test (Flow Pra screening; One Lambda Inc., 21001 Kittridge St., Canoga Park, California, U.S.A.) with a panel of micrograins covered with class I and class II purified antigens. Statistical analysis was performed using chi-square analysis or Fischer s exact test. For each test, sensibility, specificity, and positive and negative value were measured.

Among 33 patients testing positive using the classic CDC-PRA technique (17 positive for B-lymphocytes and 16 positive for both B and T lymphocytes), using cytometry, 25 were positive for anti-HLA-specific antibodies (10 among the B lymphocyte-positive patients and 15 among the B + T lymphocyte-positive patients). Two patients were shown positive only using the cytofluorimetric method. Of the 27 patients positive at cytometry, 18 were positive for class I and class II, 4 for class I, and 5 for class II. FLOW-PRA screening results were less sensitive and more specific. The results obtained by the two methods are comparable(p<0.0001). The immunogenic stimuli found responsible for immunization were: transfusion in 10 of 25 patients, pregnancies in 3/9 patients, transplant in 4/8 patients, and different immunogenic stimuli in 10/12 patients. The results were not statistically significant (p>0.05).

Data show that positivity for B lymphocytes obtained using CDC-PRA is not always linked to the development of anti-HLA antibodies, whereas positivity for B+T lymphocytes, obtained using CDC -PRA, is often linked to specific antibody development. Immune response is more often directed against class I and II antibodies. The specific detection of HLA antibodies using the cytofluorimetric method allows us to identify patients at risk for rejection, and it suggests that red cells should be filtrated to prevent anti-HLA immunization secondary to transfusion in transplantation candidates.