Part 4/8:
T cells are pivotal in mounting cell-mediated immunity. They constantly survey tissues for pathogens, recognizing peptides or lipids displayed by MHC molecules. Based on their function and surface markers, T cells are broadly classified into:
Helper T cells (CD4+): These cells assist in stimulating B cells to produce antibodies and activate macrophages, facilitating humoral and innate responses.
Cytotoxic T cells (CD8+): These directly kill infected or malignant cells by recognizing antigen peptides presented on MHC class I molecules.
The distinction hinges on the expression of either the CD4 or CD8 co-receptor, which guides their MHC restriction and functions.