Immunological aspects of immunodeficiency diseases part 51

In humans, T-B-SCID is most common (50% of total) caused by mutations of the recombinase-activating genes, RAG1 or RAG2. RAG1 and RAG2 are enzymes responsible for introducing double stranded DNA breaks, which initiate V(D)J gene rearrangements required for generating T- and B-cell receptors for antigen. Without normal RAG1 and RAG2 function, T- and B-cell development is arrested early in ontogeny, producing T-B-SCID.