1. Department of Physiology, Free University of Aguascalientes, Aguascalientes, Mexico
2. Departamento de Bioquímica, Escuela Superior de Medicina, Instituto Politécnico Nacional, México D.F., México
3. Department of Pathology, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada
4. Department of Immunology, Faculty of Medicine, The University of Manitoba, Winnipeg, MB, Canada