Biological Systems MCAT Practice Exam

Which type of T cells are responsible for activating B cells and other T cells?

1. T killers

2. Memory T cells

3. T helper cells

4. Cytotoxic T cells

The correct answer is: T helper cells

T helper cells play a crucial role in the immune response by activating B cells and other T cells. These cells express the CD4 glycoprotein on their surface, which enables them to recognize antigens presented by MHC class II molecules on antigen-presenting cells. Upon activation, T helper cells release cytokines that stimulate B cells to produce antibodies and enhance the activity of cytotoxic T cells, among other immune functions. This collaborative action is essential for a robust immune response, particularly in combating extracellular pathogens. The role of T helper cells is vital in both humoral immunity (mediated by B cells) and cell-mediated immunity (mediated by cytotoxic T cells). Their ability to coordinate various aspects of the immune system highlights their importance in maintaining effective immunity against a diverse range of pathogens.