This response is highly adaptable b/c of somatic hypermutation (defined as a process of accelerated somatic mutations), and V(D)J recombination (defined as an irreversible genetic recombination of antigen receptor gene segments). A small number of genes can generate a vast number of different antigen receptors, uniquely expressed on each individual lymphocyte. Since the gene rearrangement leads to an irreversible change in the genetic code, cellular prodigy (memory T cells and memory B cells) inherit the same receptor specificity that confer long-lived specific immunity.