Major histocompatibility complex is crucial for a T-cell's ability to:

The function of the major histocompatibility complex (MHC) is critical for T-cells, as it plays a fundamental role in the immune system's ability to distinguish between self and nonself entities. MHC molecules are surface proteins found on cells that present peptide fragments from proteins that are either produced within the cell (self) or derived from pathogens (nonself) to T-cells.

When a T-cell encounters an MHC molecule presenting a peptide, it can recognize whether the peptide is part of the body's own proteins or if it is derived from pathogens such as viruses or bacteria. This recognition process is essential because it enables the T-cell to initiate an appropriate immune response. When T-cells detect foreign peptides (nonself), they can become activated and start attacking these pathogens, while they typically do not respond strongly to self peptides, helping to prevent autoimmune reactions.

Therefore, the crucial role of MHC in helping T-cells recognize self from nonself is fundamental to maintaining the immune system's functionality and ensuring that the body can effectively defend itself against infections while avoiding damage to its own tissues.