He shipped out to the southwest Pacific Theater with the 105th General U.S. Army Hospital, as its chief laboratory officer. The 105th saw action in New Guinea, the Solomon Islands, and the Philippines. Coons was discharged from the Army at the end of 1945 with the rank of Major (O4). He was awarded the Asiatic-Pacific Campaign Medal and the World War II Victory Medal. Career at Harvard Medical School Returning to Boston, Coons continued his work on immunohistochemistry, in collaboration with Louis Fieser—an organic chemist—and his colleagues. Before the war, they had been successful in coupling anthracene isocyanate—a fluorophore—to antipneumococcus antibodies. The resulting product retained its immunological function, and was capable of agglutinating pneumococcal bacteria. In addition, the organisms were brightly fluorescent and could be seen easily with a microscope that was fitted with an excitational ultraviolet light source. This basic laboratory paradigm was later applied to many antigens and antibodies,Coons AH, Snyder JC: Localization of antigen in tissue cells; antigens of rickettsiae and mumps virus. J Exp Med 1950; 91: 31-38.Coons AH: Fluorescent antibody methods. Gen Cytochem Methods 1958; 1: 399-422. launching the clinical disciplines of diagnostic immunofluorescence microscopy for bacteriology and immunology, immunocytology, and immunohistochemistry in anatomic pathology. These methods are widely used today, globally, in clinical medicine and cell biology. Many scientists spent time as fellows in Coons's Harvard laboratory. They, in turn, further developed the technique of immunohistology, as applied to electron microscopy and light microscopy. Coons progressed through the academic ranks at Harvard Medical School, and in 1953 was appointed Career Investigator for the American Heart Association. He completed additional work on in vitro and in vivo antibody production and the condition of immunological "tolerance".Sercarz EE, Coons AH: The absence of antibody-producing cells during unresponsiveness to BSA in the mouse. J Immunol 1963; 90: 478-491. In recognition of his achievements, Coons was given the prestigious Albert Lasker Award in Basic Research in 1959. Coons was admitted as a member of the National Academy of Sciences in 1962. In 1970, he was given a named Harvard University Chair in the Department of Bacteriology and Immunology, and later, in the Department of Pathology. He was president of the American Association of Immunologists (1960–1961) and a councillor and president of the Histochemistry Society'', and was given several other awards and international honorary academic degrees. These included the Paul Ehrlich Award in 1961, the Passano Award in 1962, the