Antigenrezeptorspezifitäten

Antigenrezeptorspezifitäten refers to the ability of antigen receptors on immune cells to recognize and bind to specific antigens. These receptors are crucial for the adaptive immune system's ability to mount a targeted response against a vast array of pathogens and foreign substances. The primary antigen receptors are the B cell receptor (BCR) and the T cell receptor (TCR).

BCRs, found on B lymphocytes, are typically membrane-bound antibodies that recognize intact antigens, including proteins, polysaccharides, and lipids. The specificity of a BCR is determined by the unique variable regions of its heavy and light chains, which form the antigen-binding site. Each B cell expresses BCRs with a single, distinct specificity.

TCRs, expressed on T lymphocytes, are more complex and recognize peptide fragments of antigens that are processed and presented by MHC molecules on the surface of antigen-presenting cells. The TCR also consists of variable regions that confer specificity, but its recognition is dependent on the interaction with MHC class I or class II molecules. This dual recognition ensures that T cells respond only to foreign antigens presented in a specific context, preventing autoimmune reactions.

The immense diversity of antigen receptor specificities is generated through a process called V(D)J recombination, a genetic mechanism that shuffles and combines different gene segments encoding the variable regions of BCR and TCR chains. This combinatorial diversity allows the immune system to generate a repertoire of receptors capable of recognizing virtually any conceivable antigen. This exquisite specificity is fundamental to the immune system's ability to distinguish between self and non-self, a critical aspect of immune surveillance and defense.