Steven M Singer


Affiliate member, Lombardi Comprehensive Cancer Center Professor, Department of Microbiology and Immunology


(On leave 2015-16)


Department of Biology


My research centers mainly on the protozoan parasite Giardia lamblia. Giardia replicates in the small intestines of many species of mammals and is a major cause of human diarrheal disease throughout the world. In the U.S. Giardia infections are mainly found in campers and hikers who forgot to treat their water as well as in day care and nursing home situations. In addition to its medical importance, Giardia is also one of the first eukaryotic cells to have branched off the main line of eukaryotic evolution and is therefore of interest for studies of evolution.

The research area in the lab focuses on the host's immune response to the parasite. While both humans and mice produce a strong antibody response during infections with Giardia, we have shown that antibodies are not required to control acute infections with this parasite. Instead, a CD4+ T cell response is absolutely required to control the infection. The cytokine interleukin-6 (IL-6) is also absolutely required and we are currently determining which cells produce IL-6 during Giardia infections since not only CD4+ T cells, but also intestinal mast cells and intestinal epithelial cells can produce large amounts of this cytokine. More recently, we have shown that mast cells plays an integral role in immunity to this infection and we are now connecting T cell responses and mast cell responses to physiological changes in the intestine that help eradicate this infection.