This clicker case is an adaptation of a case by Annie Prud'homme-Généreux that was originally published by the National Center for Case Study Teaching in Science titled "Resistance Is Futile ... or Is It? The Immunity System and HIV Infection." It has been reformatted to use clickers and a PowerPoint presentation, and is reduced in scope to fit a 90-minute class. The case uses the results of the landmark paper by Paxton and his colleagues (Paxton et. al., 1996) that offered the first breakthrough in understanding why some people are protected against HIV infection. During the presentation, students make hypotheses, predict the outcome of experiments, and compare their predictions with real data. This adaptation was developed for use in an undergraduate, lower-division human physiology class when covering the immune system. Instructors interested in using it are advised to read the teaching notes for the original case for a full background.