Inserm U1050 1 article published in JoVE Immunology and Infection Imaging Ca2+ Responses During Shigella Infection of Epithelial Cells Yasmine Smail1,2,3,4, Chunhui Sun1,2,3,4, Laurent Combettes5, Guy Tran Van Nhieu1,2,3,4 1Equipe Communication Intercellulaire et Infections Microbiennes, Centre de Recherche Interdisciplinaire en Biologie (CIRB), Collège de France, 2Institut National de la Santé et de la Recherche Médicale (Inserm), U1050, 3Centre Nationale de la Recherche Scientifique (CNRS), UMR7241, 4MEMOLIFE Laboratory of Excellence and Paris Sciences et Lettres, 5Inserm, UMRS1174, Université Paris Sud Here, we present protocols to visualize calcium (Ca2+) responses elicited by HeLa cells infected by Shigella. By optimizing the parameters of bacterial infection and imaging with Ca2+ fluorescent probes, atypical global and local Ca2+ signals induced by bacteria over a large range of infection kinetics are characterized.