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Expression of HLA system antigens on placenta
Transplantation
|December 1, 1976
Summary
Placenta expresses low levels of human leukocyte antigen (HLA)-A and -B antigens, similar to beta2-microglobulin, but much less than spleen cells. This may explain the absence of immune responses to trophoblast antigens.
Area of Science:
- Immunogenetics
- Reproductive immunology
- Cellular immunology
Background:
- Human leukocyte antigen (HLA) expression on placental cells is crucial for maternal-fetal tolerance.
- Understanding HLA antigen levels in the placenta is key to deciphering immune interactions during pregnancy.
Purpose of the Study:
- To quantify the expression levels of HLA-A and -B antigens on human placenta.
- To compare placental HLA antigen expression with that of spleen lymphocytes and investigate the role of low expression in immune tolerance.
Main Methods:
- Purified placenta plasma membrane preparations were used.
- Antigen activities of HLA-A, HLA-B, and beta2-microglobulin were estimated.
- Potential contamination from maternal blood or tissue was rigorously excluded.
Main Results:
- Maternally and paternally inherited HLA-A and -B antigen activities, along with beta2-microglobulin, were expressed at similar, low levels (<5% of spleen lymphocyte levels).
- No significant expression of Ia antigens was detected on the placenta.
- The low expression of HLA antigens on trophoblast cells was confirmed, ruling out contamination.
Conclusions:
- The significantly reduced expression of HLA-A and -B antigens on the placenta may be a mechanism to evade maternal cellular immune responses.
- This low antigenicity could facilitate the acceptance of the semi-allogeneic fetus by the maternal immune system.
- The findings suggest a novel pathway for immune tolerance at the maternal-fetal interface.