Which type of T cell responds to endogenous antigens?

• A. CD-4
• B. CD-8
• C. Cytotoxic T cells
• D. Helper T cells

Answer: (B)

The response to endogenous antigens is primarily carried out by CD-8 T cells, also known as cytotoxic T cells. Endogenous antigens refer to proteins that are produced within the cell, such as those from viruses or mutated proteins in cancer cells. These proteins are processed by the cell and presented on the surface via Major Histocompatibility Complex (MHC) class I molecules.

CD-8 T cells have specific receptors that recognize these MHC class I-peptide complexes, allowing them to identify and eliminate infected or abnormal cells. This process is crucial for maintaining cellular health and defending against intracellular pathogens, making CD-8 T cells essential players in the immune response against viruses and tumor cells.

In contrast, CD-4 T cells (or helper T cells) primarily recognize exogenous antigens presented by MHC class II molecules, which are typically derived from extracellular pathogens. Their role is more focused on coordinating the immune response by activating other immune cells rather than directly killing infected cells. Therefore, when discussing the direct response to endogenous antigens, CD-8 T cells are the key players.