How are T cells classified by the type of receptors they express?

• A. By the presence of B-Cell receptors
• B. By the presence of CD28 receptors
• C. By the presence of CD4 or CD8 receptors
• D. By their secretion of antibodies

Answer: (C)

T cells are classified primarily based on the type of co-receptors they express on their surface, specifically CD4 or CD8 receptors.

CD4 T cells, also known as helper T cells, play a crucial role in enhancing the immune response by assisting other immune cells, including B cells and cytotoxic T cells. They primarily recognize antigens presented by major histocompatibility complex (MHC) class II molecules, which are found on professional antigen-presenting cells.

On the other hand, CD8 T cells, commonly referred to as cytotoxic T cells, are involved in directly killing infected or cancerous cells. They recognize antigens presented by MHC class I molecules, which are present on nearly all nucleated cells.

The distinction between CD4 and CD8 is fundamental in understanding the various roles that T cells play in the adaptive immune response. This classification helps in identifying their specific functions and mechanisms within the immune system, allowing for targeted therapeutic strategies in immunology and medicine.