T lymphocytes

T cells recognize antigen via the T-cell receptor, a two-chain receptor which is homologous to Ig and has constant and variable regions. Unlike antibody, the T-cell receptor serves only antigen recognition and has no intrinsic effector function; thus its constant region is much simpler than that of Ig. The basic construction and genetics of the T-cell receptor are very similar to Ig; it too has three CDRs, the most variable of which is CDR3 which probably comes into contact with the antigen molecule.

However, there is a fundamental difference between T and B antigen recognition, since T cells interact only with 'processed' antigen bound to a major histocompatibility complex (MHC) molecule on a second cell. Therefore T-cell activation requires 'antigen presentation'; consequently T cells predominantly recognize the primary sequence of antigenic peptides and are insensitive to native conformation.

There are two principal types of antigen-presenting MHC molecule: class I and class II. Each MHC molecule contains a peptide-binding site which is capable of binding a large number of peptides, each predominantly 10 to 20 amino acids long. The antigen-binding region of the T-cell receptor interacts with the exposed surface of the peptide bound within the MHC binding site, and also with the sides of the binding site themselves.

Sleep Apnea

Sleep Apnea

Have You Been Told Over And Over Again That You Snore A Lot, But You Choose To Ignore It? Have you been experiencing lack of sleep at night and find yourself waking up in the wee hours of the morning to find yourself gasping for air?

Get My Free Ebook

Post a comment