In response to a viral strain decreasing class I MHC expression, which immune cells are likely to be more effective against the parental virus?

When class I MHC expression decreases due to a viral strain, CD8+ T lymphocytes—also known as cytotoxic T cells—become less effective at recognizing and killing infected cells. This is because CD8+ T cells primarily recognize viral antigens presented by class I MHC molecules on the surface of infected cells. A reduction in class I MHC means fewer targets for CD8+ T cells.

Natural killer (NK) cells, on the other hand, are specifically designed to respond to infected or malignant cells that exhibit low or absent class I MHC expression. They do not rely on antigen presentation in the same way that CD8+ T cells do. Instead, NK cells are activated when they detect a lack of class I MHC on the surface of cells, as this is often a sign of viral infection or other intracellular abnormalities. Therefore, in the context of a viral strain that decreases class I MHC expression, NK cells can become more effective since they can directly recognize and eliminate these compromised cells without the need for class I MHC-mediated antigen presentation.

This ability gives NK cells a distinct advantage when dealing with viruses that downregulate class I MHC, making them critical in the early response to viral infections and in