Impaired cell-mediated immunity in Papua New Guinean infants.

Immune function was studied in Papua New Guinea highland infants with pneumonia, healthy highland controls and expatriate controls under the age of 15 months. Delayed-type hypersensitivity to tuberculin was depressed in highland pneumonia patients and highland controls as were CD4/CD8 T-lymphocyte ratios. The differences between highland and expatriate infants were more pronounced after 6 months of age, suggesting an environmental effect. Serum immunoglobulin and complement concentrations were higher in highland infants than in expatriate controls. Indices of nutritional status were similar in highland and expatriate infants but iron deficiency was more common in the highland infants in the study.