My career has been based on work on the pathogenesis, characterization and treatment of human immune deficiency diseases. I am Professor of Medicine, Pediatrics and Immunology at Mount Sinai Medical Center, and Program Director for Allergy Immunology Fellowship Training. I obtained my PhD in immunology, and fortunately found myself in the world of Primary Immune Deficiency, leading to both basic research and clinical care. My training is in Internal Medicine but I am also Professor of Pediatrics at Mount Sinai, work in this field quite practical. I have been the Program Director of the Allergy/Immunology fellowship for the past 15 years, and have seen our terrific graduating fellows take their own places in academic medicine. At Mount Sinai, I established the Primary Immune Deficiency Clinic, a referral service for infants, children and adults with known or suspected primary immune deficiency diseases; patients are referred from all over the United States and other countries. I am a past President of the Clinical Immunology Society, and established the Primary Immune Deficiency Summer School Program for teaching fellows; our graduates now number over 400 physicians and research scientists. I am a founder and PI of the USIDNET, and NIH supported Research Consortium of the Immune Deficiency Foundation. This field has become a more and more exciting in the past years, and I have been able to devote significant time to research, having been continuously well-funded by the NIH for the past 3 decades. My laboratory interests have included long-standing investigations on the defects of human B cells, based on the commonest genetic defects of man. These studies have proved of great value in determining how normal immunity is organized and ultimately controlled.