Progress in primary immunodeficiency.

Clinically, primary immunodeficiencies can be grouped into several well-defined syndromes. This consistent clinical picture, however, belies the enormous complexity of lymphocyte maturation and activation, and it has long been suspected that numerous distinct underlying defects give rise to primary immunodeficiencies. At a recent workshop, the molecular and genetic characterization of a handful of such defects provided tacit support for such suspicions.