[1] GOTHENBURG UNIV, DEPT PEDIAT, S-41685 GOTHENBURG, SWEDEN
[2] GOTHENBURG UNIV, DEPT MED MICROBIOL, S-41685 GOTHENBURG, SWEDEN
[3] BORAS HOSP, DEPT PEDIAT, PEDIAT OUTPATIENT CLIN, VASTRA FROLUDA, SWEDEN
[4] NICHHD, DEV & MOLEC IMMUN LAB, BETHESDA, MD 20892 USA
[5] NICHHD, BIOMETRY BRANCH, BETHESDA, MD 20892 USA