Sperm-associated and circulating IgA and IgG classes of antibodies recognise different antigens on the human sperm plasma membrane.

IgA and IgG antibodies eluted from the surface of spermatozoa obtained from 11 infertile men were used to analyse the antigens defined by each class of sperm-associated antibodies. An enhanced chemiluminescent Western blot technique was developed to detect the low concentrations of immunoglobulins present in the eluted samples. The same analysis was performed with the sperm membrane-specific antibodies isolated from the sera of 8 of the patients included in the study. Sperm-eluted antibodies reacted with a total of 18 protein bands migrating with molecular masses of between 110 and 18 kDa. Individual antibody-binding patterns differed. Furthermore, IgA and IgG antibodies from any one patient recognised different sets of antigens. In spite of the apparent heterogeneity of the antigens defined by sperm-associated antibodies, the majority of these antibodies reacted with three protein zones of 68/64, 37/36 and 20/18 kDa. The antigens defined by the sperm surface-specific antibodies obtained from the sera of eight infertile patients differed from one patient to another and, in the majority of the patients, differed from those defined by the corresponding sperm-associated antibodies. Nevertheless, two protein zones of 68/64 and 20/18 kDa were recognised by both local and systemic antibodies in 6 and 4 patients, respectively.