Definition of primary immunodeficiency in 2011: a "trialogue" among friends.

There is no clear consensus about the definition of the term primary immunodeficiency in 2011. Although there is general agreement that defects in both adaptive and innate immunity should be included, issues related to the frequency of primary immunodeficiencies, the modes of inheritance, the other types of cells involved, and the required clinical phenotype are more contentious. Three friends with an interest in both the clinical and scientific aspects of primary immunodeficiency carried out a discussion or trialogue to address some of these issues.