The indirect immunobead test for seminal antisperm antibodies and fertilization rates at in-vitro fertilization

Abstract

A series of 183 patients with positive indirect immunobead tests on semen was studied to determine the correlation in semen between specific antibody types, binding sites, antibody concentration, and fertilizing ability. IgM was present in only 44 ejaculates and was present in sufficient quantity to cause significant binding to immunobeads (i.e. >20% of motile donor spermatozoa) in only three of them. There was no correlation between the percentages of motile donor spermatozoa that bound IgA and IgG immunobeads but the two classes of beads generally bound to the same region of the spermatozoa. A total of 63 couples went on to attempt in-vitro fertilization (IVF) treatment, all with mature eggs recovered. Of these mature eggs, 44% were fertilized and cleaved normally in comparison to 68% in a group of patients with tubal disease. Fertilization rates in individuals followed a bimodal distribution with a substantial number of couples experiencing zero or very poor rates (0-20%), the mode for the remainder lying between 60 and 80%. The fertilization rate tended to decrease as the amount of antibody increased. The percentage of donor spermatozoa that bound to immunobeads, taken as the greater of IgA and IgG, was selected by logistic regression as a significant predictor of poor fertilization (rate <=25%). The predictive power of the equation was improved by including the motile normal sperm concentration but the equation could only account for a small proportion of the total variation in fertilization rate. The presence of antibodies to the sperm head was highly correlated with the antibody concentration but was not selected as a predictor of fertilization. We conclude that the nature of the antigen against which the seminal antisperm antibody is directed may be as important as the antibody concentration in affecting sperm function. There seems to be little practical value in measuring IgM in seminal plasma.