RAG1 and thymus lymphoma: As suggested by the authors, this diversity also depends on a complex interplay between the often limited immune receptor repertoire, antigen or auto‐antigen exposure, the specificity of antigen receptors, and the timing and cell type involved in immune activation.34 Moreover, because RAG1 and RAG2 are also involved in formation of the post‐cleavage complex, mutation of RAG1 rendering the enzyme proficient in DNA cleavage but deficient in post‐cleavage complex formation leads to impaired lymphocyte development and also to a predisposition to thymic lymphoma.35