[1] NIAID, Immunoregulat Lab, NIH, Bethesda, MD 20892 USA
[2] NCI, Frederick Canc Res & Dev Ctr, SAIC Frederick, Frederick, MD USA
[3] Univ Autonoma Madrid, Clin Puerta de Hierro, Serv Med Interna 1, Madrid, Spain
[4] Hosp Gen Gregorio Maranon, Microbiol Serv, Madrid, Spain