Related Experiment Video
Updated: Mar 23, 2026
Author Spotlight: Enhancing Graft Viability Assessment Through Quantitative Metrics and Innovative Reservoir Systems
Published on: August 2, 2024
HLA expression in aortic and pulmonary homografts: effects of cryopreservation
1Institute of Cardiovascular Diseases, Madras Medical Mission, Chennai.
Insights
Cardiac homografts, including aortic and pulmonary valves, are immunogenic. Human Leukocyte Antigen (HLA) class I and class II molecules are present on these tissues, influencing their potential for rejection.
Area of Science:
- Immunology
- Transplantation Biology
- Cardiovascular Surgery
Background:
- Cardiac homografts are utilized in transplantation procedures.
- Understanding the immunogenicity of these grafts is crucial for successful outcomes.
- Human Leukocyte Antigen (HLA) allo-antigens play a key role in immune responses to transplanted tissues.
Purpose of the Study:
- To investigate the presence and expression of HLA class I and class II antigens on cardiac homografts.
- To assess the impact of storage and cryopreservation on antigen expression.
- To determine the immunogenic potential of allograft aortic and pulmonary conduits and valves.
Main Methods:
- Analysis of one pulmonary and eight aortic homografts.
- Immunohistochemical staining using monoclonal antibodies against HLA class I, HLA-DR (class II), CD45, and endothelial markers.
- Evaluation of antigen expression during storage (up to 14 days) and after cryopreservation.
Main Results:
- Class I HLA antigen expression was detectable on the endothelium of vessel walls for the first 4-5 days of storage, diminishing thereafter.
- Class II (HLA-DR) antigen expression persisted in the subendothelial layer and valve matrix for up to 12-14 days and was also found after cryopreservation.
- Endothelial lining was compromised by storage and sterilization, though intact in vessel walls after cryopreservation; however, it was not visible in released valves.
Conclusions:
- Allograft aortic and pulmonary conduits and valves possess immunogenic properties.
- Both HLA-ABC (class I) and HLA-DR (class II) antigen molecules are demonstrably present on various components of the vessel wall and valve leaflets.
- The presence of these antigens contributes to the immunogenicity of cardiac homografts.
Background:
The present study was undertaken to find out the HLA allo-antigens on cardiac homografts.
Methods And Results:
One pulmonary and eight aortic homografts were studied for the presence of major HLA class I and class II antigen expression. Cadaveric hearts were procured from the mortuary and kept in Hank's balanced salt solution with antibiotics at 4 degrees C. Bits were taken from the conduits and valves every 24 hours for 14 days during storage and snap-frozen using liquid nitrogen. A total of 1368 sections were made using a cryostat. These sections were stained using 4 monoclonal antibodies: BLA class I (MO736), class II HLA-DR (MO746), CD45 (MO701), and endothelial stain (MO616). All monoclonals were procured from DAKO. Class I antigen molecules could be demonstrated on the endothelial surface of the vessel wall from day 1 to day 4 to 5 of storage. They stained weaker and could not be demonstrated after day 10 of storage. Class I antigen molecules were positive in very fresh valves and by day 5-6 could not be seen on the valve surface. Class II (HLA-DR) antigen expression was present in the subendothelial layer from day 1 to day 12-14 of storage. They could also be demonstrated in valves and conduits released after cryopreservation. These class II staining cells were also stained by CD45 monoclonal antibody and hence could be macrophages, histiocytes or leucocytes. The endothelium was very well demonstrated in the vessel walls from day 1 to day 12-14 of storage; it could only be seen in very fresh valves. Storage in the liquid medium and sterilization procedures led to loss of endothelial lining of the valves. After cryopreservation and thawing, class I antigen molecules could not be demonstrated on the valves and conduits. Class II antigen molecules and CD45-stained cells continued to be demonstrated in the subendothelial layer and the valve matrix. The endothelium was intact in the vessel wall after cryopreservation and thawing, but could not be seen in the released valves.
Conclusions:
Allograft aortic and pulmonary conduits and valves are immunogenic, and HLA-ABC and HLA-DR antigen molecules can be demonstrated on different components of the vessel wall and valve leafets.
