Masters School 1 article published in JoVE Immunology and Infection Detection of Trypanosoma brucei Variant Surface Glycoprotein Switching by Magnetic Activated Cell Sorting and Flow Cytometry Danae Schulz1,2, Monica R. Mugnier1, Catherine E. Boothroyd1,3, F. Nina Papavasiliou1 1Laboratory of Lymphocyte Biology, Rockefeller University, 2Department of Biology, Harvey Mudd College, 3Masters School African trypanosomes grown in vitro undergo antigenic variation at a low rate, such that populations are made up of parasites expressing a dominant variant surface glycoprotein (VSG) type and a small population of "switched" variants. This protocol describes a fast method for detecting and quantifying these populations.