Lloyd's research contributions have had direct clinical and translational impact on the field of mucosal immunity and inflammatory bowel disease. Despite his expertise in mouse models of inflammation, Lloyd always focused his research on human disease. The Kunkel lab was exploring immunoglobulin secretion and hypogammaglobulinemias. Lloyd advanced the field by creating T-cell hybridomas to demonstrate the production of B-cell differentiation factors capable of enhancing IgA production and secretion by isolated human B cells. He also used these hybridomas to demonstrate immunoglobulin isotype switching, helping to explain the hyper-IgM syndrome. Lloyd is perhaps best known for his contributions to understanding the interaction between human gut epithelial cells and the immune system. He demonstrated the antigen-presenting capability of epithelial cells and their interaction with T cells, resurrecting the field of CD8+ regulatory T cells. He identified gp180 (a member of the CEACAM family) as a novel CD8 ligand on epithelial cells, noting a loss of expression in Crohn's disease. He contributed seminal observations to our understanding of food allergy and oral tolerance, which has importance for developing vaccines for a variety of diseases including HIV.