[1] Natl Med Ctr Siglo XXI, Specialties Hosp, IMSS, Med Res Unit Immunochem, Mexico City, DF, Mexico
[2] Specialties Hosp, Natl Med Ctr Siglo 21, IMSS, Gastrointestinal Surg Serv, Mexico City, DF, Mexico
[3] IMSS, Clin Epidemiol Serv, Reg Hosp 1, Mexico City, DF, Mexico
[4] Natl Inst Perinatol, SSA, Infectol & Immunol Dept, Mexico City, DF, Mexico
[5] Natl Inst Perinatol, SSA, Cellular Biol Dept, Mexico City, DF, Mexico
[6] IPN, Grad Program Immunol, ENCB, Mexico City, DF, Mexico
[7] Natl Med Ctr Siglo XXI, Specialties Hosp, Internal Med Serv, IMSS, Mexico City, DF, Mexico
[8] Natl Med Ctr La Raza, Unit Epidemiol Surveillance, IMSS, Mexico City, DF, Mexico
[9] Womans Hosp, Div Res & Educ, Minist Hlth, Mexico City, DF, Mexico
[10] Natl Autonomous Univ Mexico UNAM, Fac Chem, Mexico City, DF, Mexico
[11] Univ Oxford, Oxford Biomed Res Ctr, Oxford, England
[12] Univ Oxford, Nuffield Dept Med, Oxford Martin Sch, Oxford, England