• Sperm;
  • antibodies;
  • immunobeads;
  • agglutination

ABSTRACT: Two procedures were developed and evaluated that used either larger or smaller volumes for the detection of sperm antibodies in serum by means of an indirect immunobead test (IBT). The immunobeads, coated with rabbit antibody to each of the major human immunoglobulins (IgG, IgA, or IgM), were mixed with preparations of donor sperm, onto which antibody had been coated by passive transfer from various serum samples. The results of the IBT could be evaluated in various ways: (1) positive or negative; (2) if positive, whether binding is to the tail, the head, or the head and tail of the sperm cells; (3) if positive, whether binding is by IgG, IgA, or IgM. The diverse IBT results were obtained from a group of 50 serum samples; these sera were also tested by two sperm agglutination methods; the gelatin agglutination test (GAT) and the tube-slide agglutination test (TSAT). There was an excellent agreement between the IBT and the GAT; it was not as good between the IBT and the TSAT. However, considering both agglutination methods together, 90% of the IBT-positive sera were agglutination-positive. In terms of morphological sites, tail binding occurred in 27 of 31 sera, head binding in 12 of 31 sera, and head-tail binding in 15 of 31 sera. The number with tail binding was very close to the number that were GAT-positive (26). As for the immunoglobulins, the most frequent class was IgG. IgA was 83% as frequent and IgM was only 25% as frequent as IgG. In a larger group with only IgG and IgA, of 31 IBT-positive sera, 26 showed IgG and 23 showed IgA; 18 showed both. Hence, only eight showed IgG exclusively, and only five showed IgA exclusively. One final point is that several sera with GAT titers of only 4 were IBT-positive, adding strength to the concept that such a low GAT titer does have antibody significance.