What type of molecules do T cells primarily recognize?

T cells primarily recognize Major Histocompatibility Complex (MHC) molecules because these molecules present antigenic peptides on the surface of cells. MHC molecules are critical for the immune response, as they bridge the innate and adaptive immune systems by displaying processed pieces of antigens (peptides) derived from pathogens.

When a pathogen infects a cell, the proteins from that pathogen are broken down into smaller peptide fragments. These peptides are then loaded onto MHC molecules within the cell and transported to the cell surface. T cells, specifically CD4+ and CD8+ T cells, have receptors (T cell receptors, TCRs) that specifically recognize these peptide-MHC complexes. This recognition is essential for initiating appropriate immune responses, such as the activation of helper T cells to stimulate other immune cells, or the activation of cytotoxic T cells to kill infected cells.

Other options presented do not accurately reflect how T cells recognize antigens. Antibodies are produced by B cells and recognize free-floating antigens, not processed peptide-MHC complexes. Cellular receptors are a broad category and do not specifically describe the recognition mechanism of T cells. Pathogen-associated molecular patterns (PAMPs) refer to common features of pathogens recognized by innate immune receptors,