In 2009, reports on basic and clinical immunology had an increased focus on human disease mechanisms and management. The molecular pathogenesis of familial angioedema associated with estrogen was further explored to find possible factors affecting severity, including polymorphisms in enzymes and receptors related to bradykinin pathways. A placebo-controlled clinical trial of C1 esterase inhibitor concentrate in patients with hereditary angioedema demonstrated the safety of its use and its efficacy to reduce the duration of angioedema attacks. The interaction of innate immunity and adaptive responses was further examined in several reports, establishing the significant role of Toll-like receptor stimulation for the development of optimal specific antibody responses. The 2009 update of the classification of primary immunodeficiencies introduced more than 15 new genetic defects related to the immune response, including of dedicator of cytokinesis 8 (DOCK8) mutations, which are responsible for the autosomal recessive form of the hyper-IgE syndrome. Other reports expanded the clinical spectrum of disease and improved the characterization of conditions such as warts, hypogammaglobulinemia, and myelokathexis syndrome or the occurrence of mucormycosis and Serratia species infections in patients with chronic granulomatous disease. The frequent presentation of gastrointestinal disorders in patients with humoral immunodeficiencies was recognized, and recommendations for management were reviewed. Clinical research focused on severe combined immunodeficiency included the development and implementation of a state-wide newborn screening program for this condition, a desired goal considering the significant reduction of mortality rate when the diagnosis is made early before opportunistic infections occur.