Artemis sheds new light on V(D)J recombination.

V(D)J recombination represents one of the three mechanisms that contribute to the diversity of the immune repertoire of B lymphocytes and T lymphocytes. It also constitutes a major checkpoint during the development of the immune system. Indeed, any V(D)J recombination deficiency leads to a block of B-cell and T-cell maturation in humans and animal models, leading to severe combined immunodeficiency (T-B-SCID). Nine factors have been identified so far to participate in V(D)J recombination. The discovery of Artemis, mutated in a subset of T-B-SCID, provided some new information regarding one of the missing V(D)J recombinase activities: hairpin opening at coding ends prior to DNA repair of the recombination activating genes 1/2-generated DNA double-strand break. New conditions of immune deficiency in humans are now under investigations and should lead to the identification of additional V(D)J recombination/DNA repair factors.