Legends of allergology and immunology: Per Brandtzaeg – Pillar of mucosal immunology
Authors: Frode L. Jahnsen, Finn‐Eirik Johansen
Journal: Allergy (2021)

After graduating dental school, Per Brandtzaeg joined the Norwegian army for his mandatory national service. During his military service, he was able to work on gingivitis and his passion for research was lit. In 1962, he obtained a Fulbright scholarship to join Frederick W. Kraus's laboratory at University of Alabama in Birmingham, where he became involved in the work on the immunological defence of human mucous membranes. His work was based on immunofluorescence for the localization of immunoglobulins and other proteins in human tissue sections. When he returned to Norway in 1965, he founded the Laboratory of Immunopathology and Immunohistochemistry (LIIPAT) (Figure 1) and it was as the leader of LIIPAT for more than 40 years that Per became internationally recognized and a true leader in the field of immunology. The mucosal immune system was a new area of research. Per used physiochemical and immunochemical methods to study immunoglobulins in external secretions and defended his PhD degree in 1971 entitled ‘Human Secretory Immunoglobulins’. Staining tissue sections with antibodies were a new discipline and with novel microscope technology, he was able to perform paired immunofluorescence staining of two antigens in the same tissue section. His pioneering work of the secretory IgA system included both structural characterization of IgA and studies on its transport mechanism to external secretions. Per’s scientific breakthrough came in 1974 when he described the model by which secretory antibodies are selectively translocated through glandular and mucosal epithelia.1 Per showed that the joining chain (J chain), a small polypeptide associated with IgA and IgM polymers, was a product of plasma cells and that only J chain-containing IgA and IgM could bind the epithelial receptor protein secretory component (SC; a.k.a polymeric IgR).2 This model stimulated broad international interest in this field, and over the next few years, the ‘Norwegian’ model was supported by many laboratories and is now textbook immunology (Figure 2). In a Nature paper in 1984, he demonstrated the function of SC and J chain as the lock and key in the transport model.5 In 1989, the human pIgR/SC gene was cloned in Per's laboratory,3, 4 and the final proof that the transport model was correct came in 1998 when Per and co-workers demonstrated the absence of epithelial IgA transport in mice deficient in pIgR.5 The seminal studies on the transport of secretory antibodies were followed by a series of both clinically and basic-oriented work of mucosal immunology. Per created a strong and dynamic scientific environment where he supervised more than 40 PhD students and numerous postdocs. He was a great role model with high enthusiasm for science, creativity and his stamina, and as a supervisor, he was supportive and conscious about giving his students freedom to follow their own ideas. Per created a very good social environment at LIIPAT, and he cared greatly for both technical staff and young researchers. Brandtzaeg and co-workers performed detailed characterization of the phenotype and function of many types of immune cells at mucosal tissues and studied the immunopathology of diseases such as inflammatory bowel disease, coeliac disease, food intolerance/allergy, chronic gastritis, bronchitis, allergic rhinitis, tonsillitis, periodontitis and Sjøgren’s syndrome and various immunodeficiencies. Together, Per published more than 600 articles, eight monographs and 132 book chapters. Per was a highly acclaimed international scientist and was instrumental in turning the research field of mucosal immunology into the prominent discipline that it is today. Per became the first non-American president of the Society for Mucosal Immunology in 1994. As a sign of his position as a leading international scientist, he received numerous national and international awards. He received honorary doctorates from four European universities, and he was elected to several learned societies in Norway and abroad. The authors have no conflicts of interest.