What enzyme is crucial for junctional diversity in immune receptors?

The enzyme that plays a crucial role in junctional diversity in immune receptors is terminal deoxynucleotidyl transferase, commonly referred to as TdT. TdT is responsible for adding nucleotides at the ends of DNA during the recombination of immunoglobulin and T-cell receptor genes. This process is essential for generating a diverse repertoire of immune receptors, which enables the immune system to recognize and respond to a wide array of antigens.

During the process of somatic recombination, which occurs in developing lymphocytes, TdT adds non-templated nucleotides to the junctions where gene segments are joined. This addition of nucleotides creates variability in the immune receptor sequences, contributing to the uniqueness of each receptor. This junctional diversity is crucial for enabling a robust and adaptable immune response, as it allows for the recognition of various pathogens.

The other options provided do play important roles in immune function, but they do not specifically contribute to junctional diversity. RAG-1 is essential for initiating the recombination process but does not contribute to the diversity itself through nucleotide addition. DNA polymerase is involved in DNA synthesis and repair rather than in the diversity of immune receptors. Topoisomerase manages DNA supercoiling and