His later work on the host immune mechanisms against the protozoan parasitic disease leishmaniasis inspired a generation of immuno-parasitologists, significantly contributing to and sustaining the pre-eminent position of the United Kingdom in the field of parasitology. He served in advisory roles for such bodies as the World Health Organisation, the Medical Research Council, the Imperial Cancer Research Fund, and Direction Generale de la Recherche Scientifique et Technique, France, and also acted on the editorial boards of various journals of immunology.
The only child of Joseph and Kathleen Howard, James Howard was born in New Malden, Surrey, in 1927. From an early age he displayed a thirst for knowledge, and was fortunate to attend the enlightened Raynes Park Grammar School, which was staffed by a wartime infusion of distinguished teachers; the broadcasters Robert Robinson and Paul Vaughan were among his contemporaries. It was here that his interest in science and deep love of music were first aroused and nurtured.
Howard went on to study medicine at the Middlesex Hospital in London, after which he chose to follow a laboratory rather than a clinical career. In 1949, he met Opal Echalaz, an art student at Camberwell, whom he married in 1951, just before starting army service in Wiltshire. This was to mark the beginning of a long and happy marriage, during which she continued to paint and exhibit her paintings widely.
After completing National Service with the rank of major, Howard took up a research fellowship at the Wright-Fleming Institute, St Mary's Hospital, London, where he completed his PhD in 1957. The following year, he was appointed to a lectureship in the Department of Surgical Science at Edinburgh University, where he became Reader in Zoology. During this period he was offered a six-month fellowship by the late Professor Lewis Thomas in New York University, and this started his love of the United States, where he was to make regular visits.
In 1969, Howard returned south to head the Department of Immunobiology at the Wellcome Research Laboratories in Beckenham, Kent, where he subsequently became Director of Biomedical Research. Here, effectively and yet unobtrusively, he built up a centre of excellence in immunology and parasitology, recruiting young talents from across the world. At one stage, eight languages were spoken in his department; English was occasionally heard.
This was to be Howard's most productive period. He showed with great precision and clarity that immunological tolerance - the silencing of immune reactions to foreign materials in the body - could be brought about not only by protein antigens but also by carbohydrates such as dextrans. This suggested that carbohydrates might be used to induce acceptance of foreign organ grafts. Conversely the work also suggested that bacteria which carry substantial amounts of carbohydrate antigens on their surface might also induce immunological tolerance in such a way that the body would no longer be able to mount an immunological attack against the bacteria. Therefore carbohydrates may contribute to the successful survival and multiplication of bacteria and thus enhance their virulence.
His work on the immune response to leishmaniasis was also carried out at the Wellcome Reseach Laboratories. The disease is caused by the protozoan parasite Leishmania major, named after Lt-Gen Sir William Boog Leishman who discovered it while serving in the Army in India at the turn of the century. Howard and colleagues were the first to show that, depending on the host's genetic constitution, the parasite can either induce a protective immune response, or a disease-promoting response. Furthermore, they showed that these responses were mediated by different subsets of small white blood cells called T lymphocytes. This work generated a profound interest in leishmaniasis among immunologists, making it immunologically one of the best- understood infectious diseases.
Howard left the Wellcome Research Laboratories in 1985 to join the Wellcome Trust in London as Programme Director for infectious and tropical diseases until his retirement in 1990. His broad knowledge of science and scientists contributed significantly to the development of the trust, where his characteristic courtesy, attention to detail and intellectual integrity were much valued.
James Howard was a man with great zest for life, with wide and varied interests. His love of classical music, fine wine and the culinary art was well known. He took his laboratory skills into the kitchen. Invitations to his dinner parties were much sought after. In dress, he went against the casual trend of his fellow scientists and was seldom seen without a tie. He loved to relate amusing anecdotes and appreciated good humour. His sense of humour permeated his work, which will live long after him.
James Griffiths Howard, biomedical scientist: born New Malden, Surrey 25 September 1927; Research Fellow, Wright-Fleming Institute, St Mary's Hospital, London 1955-58; Lecturer, Senior Lecturer and Reader, Department of Surgical Science, Edinburgh University 1958-66, Reader and Head of Immunobiology Section, Department of Zoology 1966-69; Head, Experimental Immunobiology Department, Wellcome Research Laboratories 1969-74, Head, Experimental Biology Division 1974-83, Director, Biomedical Research 1984- 85; FRS 1984; Programme Director, Wellcome Trust, 1986-90; married 1951 Opal St Clair (nee Echalaz; two daughters, and one son deceased); died Sarnesfield, Herefordshire 6 October 1998.