1. Postgraduate Studies and Research Section, Superior School of Medicine, National Polytechnic Institute, 11340 Mexico City, México
2. Morphology Coordination, Department of Basic Disciplinary Training, Superior School of Medicine, National Polytechnic Institute, 11340 Mexico City, México
3. HLA Laboratory, National Institute of Respiratory Diseases Ismael Cosío Villegas, 14080 Mexico City, México