• Zona pellucida;
  • infertility;
  • immunoglobulins;
  • human

ABSTRACT: The presence of zona pellucida antibodies was sought in a group of ten women with infertility of unknown cause. The reaction of these sera with ova was compared to the reaction obtained with a control antizona pellucida serum produced by the immunization of a rabbit with 8,000 solubilized hamster zonae pellucidae. This antiserum reached a maximum titer of 1 in 256 as measured by an immunoprecipitation assay and of 1 in 1,024 as measured by indirect immunofluorescence. It is tissue-specific but is not species-specific.

With the indirect immunofluorescence technique on ova obtained from different species, the sera of eight of the ten patients gave a positive reaction with at least one type of test ova: three patients gave a positive reaction with hamster ova, six with porcine ova, and two with monkey ova. One infertile woman presented a positive reaction on hamster ova and another on pig ova as detected with all three types of γ-globulins. Two other patients presented a positive reaction with the anti-IgG and -IgM on porcine ova. The titer of the reaction never rose above one in four in any of the positive cases.

Adsorption of the sera with fresh erythrocytes from human, hamster, and porcine blood did not change the titer or the intensity of the fluorescent reaction on ova. This indicates that the positive reactions are not due to nonspecific heteroagglutinins. Adsorption of the sera with formalin-fixed erythrocytes from human and porcine blood completely abolished the fluorescent reaction. However, the latter treatment, applied to a dihydrotestosterone antiserum and a β-hCG antiserum also greatly diminished the binding of hormones to these antisera; fresh erythrocytes did not adsorb the antibodies in these two antisera. This demonstrates that formalin-fixed erythrocytes are not suited for adsorption of sera before testing for specific autoantibodies to the zona pellucida in infertile women.

None of the sera from the infertile women gave a positive reaction with human pre-ovulatory or post-ovulatory ova or with frozen sections of human ovary. None of the sera produced an inhibition of in vitro fertilization of hamster ova. On the contrary, the control zona pellucida antiserum completely blocked in vitro fertilization. Furthermore, in a group of pregnant women, 2 of 11 exhibited a positive reaction with hamster ova while 6 of 28 showed a positive reaction with porcine ova.

These results suggest the presence of low titer zona pellucida antibodies in 8 of the 10 infertile women. The importance of these antibodies in their infertility remains to be established.