STUDY OF ANTISPERM ANTIBODIES BOUND TO THE SPERM CELL-SURFACE AND THEIR RELATIONSHIP TO CIRCULATING ASA

PROBLEM: Direct and indirect tests for antisperm antibody (ASA) detect ion are commonly used in laboratories for the diagnosis of male immuno logical infertility. Even though the two kinds of tests study the same immunological phenomena, frequently no perfect correlation is found e ven on large series of patients and with precise statistical models. T he aim of the present investigation was to try to establish whether bi ological models can explain the antibody test results and if a predict ive threshold can be established for expected positivity/negativity. M ETHOD: The data relate to 667 patients, who were screened using the Di rect Immunobead test (d-IBT) for ASA bound to the sperm surface and wi th the gelatin and tray agglutination test (GAT and TAT) in sera for c irculating ASA, Correlations were studied and cases of no correlation were further analyzed. RESULTS: The number of patients with a clinical ly significant positivity to d-LBT (binding percentage greater than or equal to 20%) was 134 (20.1 % of total patients). The analysis of the results of direct and indirect tests shows that the discordances are due to differences in the Ig class of immunization or to the site of e pitopes involved. In fact, as far the Ig class is concerned, if d-IBT shows a prevalent or exclusive IgG or IgA positivity, this results in a poor correlation between binding percentage to d-IBT and GAT-TAT tit ers. If both the Ig classes are involved, the level of positivity of t he two kinds of test are strictly related. As far as the site of Ag-Ab reaction on the sperm surface is concerned, the wide immunization inv olving all the surface sperm antigens (mixed), shown by d-IBT, is rela ted to higher indirect test titers. CONCLUSION: Local and systemic ant isperm immunizations are strictly related and a predictive threshold o f expectation can be established to explain even apparently discordant direct and indirect results.