The processing requirements include successful completion of: 1  The application process, which includes a background and polygraph examination, a medical examination, a physical fitness evaluation, and a written examination; 2  24-26 weeks of intensive Academy training.
The cell membrane, being exposed to the outside environment, is an important site of cell-cell communication. As such, a large variety of protein receptors and identification proteins, such as antigens, are present on the surface of the membrane.
It was not until the discovery of how the TCR recognizes antigen that the role of MHC genes in immune responses was understood. The TCR was shown to recognize antigenic peptides in association with MHC molecules. T cells recognize portions of protein antigens that are bound non-covalently to MHC gene products.