Antibodies to the zona pellucida in mares.

This research focuses on testing the presence of antibodies to the zona pellucida (the outer layer of mammalian oocytes) in horses, particularly mares with unexplained infertility. The study discovered that out of 65 infertile mares, 7 had antibodies reactive to porcine zona pellucida.

Study Methodology and Findings

• The study began by examining cross-reactivity between the equine zona pellucida and the porcine zona pellucida, finding that they share common antigen(s). As a result, porcine oocytes (immature egg cells) were used to test for the presence of zona antibodies in horse serum.
• Serum samples were collected from 65 mares infertile due to unexplained causes. Testing showed that 7 mares were strongly positive for antibodies reactive to the porcine zona pellucida. This was determined using an indirect immunofluorescence method, a technique which utilizes fluorescent light to visualize where certain antibodies bind in a sample.
• Further analysis of the 7 mares, aged between 8 and 23 years, revealed that 2 were nulliparous (had never given birth) and 5 were multiparous (had given birth to more than one foal).
• To confirm these findings, equine oocytes covered in zona pellucida were treated with serum from 4 mares previously identified as zona positive and 1 mare identified as zona negative. The reaction was found to be the same when porcine zona-coated oocytes were treated with the same sera, affirming the validity of the initial results.

Further Investigation

• In a second group of mares, the researchers investigated whether this phenomenon occurred in relation to age. They found that in both a group of 20 mares aged 20 years or older and a group of 20 mares aged 10 years or younger, no zona antibodies could be detected.
• This led to the conclusion that the presence of zona antibodies is not age-dependent in mares but could be a factor contributing to unexplained infertility.