Which type of T-cells are primarily involved in the rejection of transplanted organs?

The rejection of transplanted organs is primarily mediated by CD8+ T cells, also known as cytotoxic T lymphocytes. These cells are crucial in the immune response because they can directly recognize and kill cells that present foreign antigens, such as those found on transplanted organ tissues.

When a transplant occurs, the recipient’s immune system identifies the foreign tissues as being non-self due to the differences in human leukocyte antigens (HLA) between the donor and recipient. CD8+ T cells respond to these differences by recognizing the antigens presented by Major Histocompatibility Complex (MHC) class I molecules on the surface of the transplanted cells. This interaction leads to the activation of CD8+ T cells, which then proliferate and differentiate into effector cells capable of inducing apoptosis in the target cells, ultimately resulting in the damage and rejection of the transplanted organ.

CD4+ T cells do play a role in the rejection process, primarily by assisting in the activation of other immune cells and orchestrating the immune response, but it is the CD8+ T cells that are directly responsible for the cytotoxic activity against the donor's cells. Regulatory T cells are involved in maintaining tolerance and preventing unwanted immune responses, while natural