Kaplan Nursing Entrance Practice Exam

What type of cells do T cells recognize in the human immune system?

1. Healthy cells

2. Self cells

3. Non-self cells

4. Infected cells

The correct answer is: Non-self cells

T cells primarily recognize non-self cells, which include cells that are infected by viruses or have become cancerous. This recognition is essential for the adaptive immune response, as it allows T cells to distinguish between the body’s own healthy cells and those that are presenting abnormal signals indicative of infection or malignancy. In the immune system, T cells inspect the peptide fragments presented on the surface of cells through Major Histocompatibility Complex (MHC) molecules. MHC class I molecules present antigens from within the cell to CD8 T cells, typically signaling the presence of intracellular pathogens, like viruses. This is a crucial mechanism for identifying infected cells that are not functioning normally, which is why T cells can respond specifically to these threats. The other cell types mentioned yield different responses: healthy cells do not generally raise an immune response from T cells since they do not display abnormal signals; self cells reference the body's own cells and, under normal circumstances, are recognized and tolerated by T cells to avoid autoimmunity; infected cells are indeed targeted by T cells but fall under the broader category of non-self. Thus, identifying non-self cells accurately encapsulates the T cells’ role within the immune system.