Lymphocyte alloantigens of the horse. II. Antibodies to ELA antigens produced during equine pregnancy.

The research explores the maternal immune response to specific antigens during horse pregnancies. It finds that most mares produce cytotoxic antibodies as a reaction to paternal lymphocyte alloantigens, which are tied with the equine lymphocyte antigen (ELA) system during pregnancy, highlighting a possible correlation between ELA incompatibility in pregnancy and the generation of these antibodies.

Maternal Immune Response during Horse Pregnancy

• The study provides evidence of a consistent immune response from the mother during horse pregnancies.
• Horse mothers (mares) produced cytotoxic antibodies when stimulated by pregnancy. These are substances that can destroy or harm other cells.
• The cytotoxic antibodies produced are majorly directed against antigens that are part of the equine lymphocyte antigen (ELA) system, which is the Major Histocompatibility Complex (MHC) in horses. The MHC is a set of genes that control an animal’s immune response.

Impact of ELA Incompatibility on Antibody Production

• The research conducted experimental pregnancies using 12 mares and 4 stallions. In 16 of these pregnancies, there was a correlation observed between ELA incompatibility (differences in the ELA genetics of the mare and the stallion) and the production of these antibodies in the mare.
• In pregnancies where there was ELA incompatibility, the antibodies were first detected very early in the pregnancy, often by the 60th day of a 336-day duration pregnancy.

Relation between Paternal ELA Antigens and Antibody Response

• The strength or the titre of the cytotoxic antibody response seemed to change with the paternal ELA antigens expressed by the fetus.
• The presence of antibody corresponding to ‘third party’ alloantigens from prior pregnancies did not alter the kinetics of antibody appearance in a current pregnancy.
• Evidence of an anamnestic response was observed in second pregnancies where the genetic compatibility difference between the mare and the fetus remained the same as in the first pregnancy. The anamnestic response refers to the immune system’s enhanced response to an antigen it has encountered before.

Widespread Presence of These Antibodies

• The research found that serum samples from approximately 90% of mares that had given birth on horse farms in New York State contained antibodies reactive to paternal lymphocyte alloantigens.