Mastering A&P Immune System Practice Test 2026 - Free Immune System Practice Questions and Study Guide

T cells specifically recognize processed fragments of protein antigens that are displayed on the surfaces of body cells. This process is a crucial part of the adaptive immune response. When an antigen is taken up by a cell, it is processed into smaller pieces, or peptides, that can be presented on major histocompatibility complex (MHC) molecules on the cell surface. T cells have receptors that are specifically designed to bind to these peptide-MHC complexes, allowing them to detect and respond to infected or altered cells, such as those in the event of an infection or cancer.

This recognition mechanism is fundamental to the function of T cells, as it enables them to identify cells that are compromised or abnormal. For instance, major histocompatibility complex class I molecules present peptides from proteins synthesized inside all nucleated cells, alerting cytotoxic T cells to the presence of intracellular pathogens, like viruses, or abnormal proteins in cancerous cells. Meanwhile, major histocompatibility complex class II molecules present antigens from extracellular sources, which are recognized by helper T cells.

Other options do not capture the full scope of T cell recognition accurately, as they either exclude the necessary processing and presentation component or limit the types of antigens T cells can recognize. Thus,