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Updated: Aug 8, 2026
In Vitro and In Vivo Assessment of T, B and Myeloid Cells Suppressive Activity and Humoral Responses from Transplant Recipients
Published on: August 12, 2017
Cell-mediated cytotoxicity in acute rat cardiac allograft rejection: an immunological and ultrastructural study
Insights
Natural killer (NK) cells are crucial in early acute cardiac allograft rejection. Cytotoxic/suppressor T cells (Tc-s) and macrophages then worsen cardiocyte injury.
Area of Science:
- Immunology
- Transplantation Biology
- Cellular Pathology
Background:
- Acute cardiac allograft rejection involves complex immune interactions.
- Understanding the specific cellular mechanisms is vital for improving transplant outcomes.
Purpose of the Study:
- To elucidate the immune mechanisms underlying cytotoxicity in acute cardiac allograft rejection.
- To identify the roles of different immune cells in cardiocyte injury.
Main Methods:
- Immunohistochemistry, light microscopy, and electron microscopy were used.
- Observation of interactions between cardiocytes and mononuclear cells in rat cardiac allografts.
- Analysis of T cell populations (helper/inducer T cells [Th], cytotoxic/suppressor T cells [Tc-s]) and IL2R+ cells, and macrophages over time.
Main Results:
- Cardiac allografts ceased beating by day 7.
- Helper/inducer T cells (Th) and IL2R+ cells were abundant early; cytotoxic/suppressor T cells (Tc-s) and macrophages increased from day 4.
- Th/Tc-s ratios decreased significantly over time, indicating a shift in immune cell dominance.
- Natural killer (NK) cells, Tc-s, and macrophages were observed in close contact with cardiocytes.
- NK cells were prominent in the early rejection phase.
Conclusions:
- Natural killer (NK) cells play a critical role in the initial stages of acute cardiac allograft rejection.
- Cytotoxic/suppressor T cells (Tc-s) and macrophages contribute to and exacerbate cell-mediated cardiocyte injury in later stages.
- The findings highlight a sequential immune response in allograft rejection.
Abstract:
To clarify the immune mechanism of cytotoxicity in acute cardiac allograft rejection, we observed interactions between cardiocytes and mononuclear cells using immunohistochemistry and light and electron microscopy. All allografted WKA rat hearts transplanted to F344 recipients stopped beating by the 7th day after the transplantation. The population of helper/inducer T cells (Th) and IL2R+ cells was large for the first 3 days, whereas that of cytotoxic/suppressor T cells (Tc-s) and macrophages increased from the 4th day. The Th/Tc-s ratios were more than 2.0 until the 3rd day, then decreased to less than 1.0. In circulating T lymphocytes; the Th/Tc-s ratios were under 1.0 on the 1st, 6th and 7th days. Electron microscopically IL2R+ cells, Tc-s and macrophages were often seen in close contact with the plasma membrane of the cardiocytes. The majority of IL2R+ cells are NK cells, Tc-s and Th. Of these, the population of Tc-s was small until the 3rd day. Thus, NK cells play a pivotal role in the early stage of the rejection, and Tc-s and macrophages then aggravate cell-mediated cardiocyte injury.
