Immunologic effccts of pre-and postnatal polychlorinated biphenyl (PCB)/dioxin exposure in Dutch infants from birth to 18 mo of agc are explored. The total study group consisted of 207 healthy mother-infant pairs, of which 105 infants were breast-fed and 102 children were bottle-fed. Prenatal PCB exposure was estimated by the PCB sum (PCB congeners 118, 138, 153, and 180) in maternal blood and the total toxic equivalent (TEQ) level in human milk (17 dioxin and 8 dioxin-like PCB congeners). Postnatal PCBIdioxin exposure was calculated as a product of the total TEQ level in human milk multiplied by the weeks of breast-feeding. The number of periods with rhinitis, bronchitis, tonsillitis, and otitis during the first 18 mo of life was used as an estimate of the health status of the infants. Humoral immunity was measured at 18 mo of age by detecting antibody levels to mumps, measles, and rubella. White blood cell counts (monocytes, granulocytes, and Iymphocytcs) and immunologic marker analyses CD4 ' T-lymphocytes, CD8+ T-lymphocytes, activated T-lymphocytes (HLA-DR.'-CD3+), as well as T cell receptor (TcR) cyp'., TcRySt, CD4+CD45RA+ and CD4+CD45ROi' T-lymphocytes, B-lymphocytes (CDIYf andlor CD20t) and NK cells (CD16' and/or CD56+/CD3-) in cord blood and venous blood at 3 and 18 mo of age were assessed in a subgroup of 55 PrenataI and postnatal exposure to PCDD, PCDF, and PCB produce a wide spectrum of toxic effects in animals, including body weight loss, hepatotoxicity, teratogenicity, carcinogenicity, neurotoxicity, reproductive toxicity, alterations in the thy-

A 50% neutralization enzyme immunoassay (Nso-EIA) was compared with an indirect enzyme-linked immunosorbent assay (ELISA) for determining mumps virus antibodies in three consecutive serum samples from 138 children vaccinated with a live mumps vaccine at the age (in years) of 1.5. By the N50-EIA, most (132 of 138) preserum samples did not show neutralizing activity. Eight to 12 weeks after vaccination, 17 of the children were still negative, but only 7 remained so after 2.5 years, resulting in a seroconversion rate of 125 of 132 (95%). Over the same period, the neutralization geometric mean titer rose from 3.6 to 9.9. By an indirect ELISA, 128 of 138 preserum samples were found negative. The early and late postvaccination sera of 8 children were ELISA negative, resulting in a seroconversion rate of 120 of 128 (94%). Only two children remained seronegative by both methods. Seven of the late postvaccination serum samples yielded noncorresponding results, reflecting 95% correlation between both methods. Due to cross-reactivity with parainfluenza viruses, the ELISA proved to be less specific, but on the other hand, it showed a greater sensitivity than the N50-EIA.

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