As any nervous first-time mother will confirm, the initial three months of pregnancy are the most risky time: many expectant women are reluctant to inform their friends or colleagues that they are pregnant until after this period is past. It is less well known that horses suffer from similar problems, with a considerable number of pregnancies failing to progress beyond the first five weeks. The explanation is still unclear but may relate to a problem with the mare's immune system, as the latest work in the group of Christine Aurich in the Vetmeduni's Centre for Artificial Insemination and Embryo Transfer strongly suggests.
The fertilized egg, or conceptus, obviously contains contributions from the stallion as well as the mare, which means it somehow has to avoid being recognized and attacked by the mare's immune system. Horse breeders talk about maternal tolerance of the conceptus and horses as other animals have a variety of mechanisms to enable fertilization and a successful pregnancy. Maternal tolerance probably depends on wide-ranging changes to the maternal immune response. But what makes some mares better than others at adapting their immune systems?
There are indications from work in humans and mice that a particular class of immune cell, the so-called regulatory T cells or Tregs (pronounced "tea regs"), might somehow be important in maternal tolerance. Aurich and her colleagues have now developed a highly sensitive assay to measure the proportion of Tregs in the blood of horses. They used their new technique to investigate over 100 mares that were presented for artificial insemination, correlating the results with the outcome of the resulting pregnancies.
Of course, not all of the animals conceived. The scientists could find no association between the level of Tregs in the mares' blood with the success of the insemination procedure. However, they did observe clearly lower numbers of Tregs in the blood of horses that suffere
|Contact: Susanna Kautschitsch|
University of Veterinary Medicine -- Vienna