Experimental approach to the study of immune function in children with possible human immunodeficiency virus infection

The clinical immunology laboratory is often called on to assess risk in pediatric patients with clinical evidence of immunodeficiency and possible human immunodeficiency virus (HIV) exposure while antibody tests are being considered or are underway. Since non–HIV‐related conditions including neoplasia, certain viruses, and primary immunodeficiency can potentially produce lymphocyte subset imbalance and functional impairment, there is need for a laboratory approach to differential analysis of pediatric immunodeficiency. In addition, laboratory methods may also influence the results obtained. In order to investigate these issues, we screened pediatric patients with and without HIV exposure. Altered lymphocyte subset expression and function were found among non‐HIV‐infected pediatric patients. The use of percentage and absolute lymphocyte numbers was found to affect the results obtained in a significant manner. Some patients who were chronic blood transfusion recipients were found to have blocking factors, presumably alloantibodies, in serum, which affected detection of lymphocyte surface antigens. In this population, age at seroconversion was a factor influencing subsequent levels of CD4 + T lymphocytes. Significant differences in CD4+ T lymphocyte percentages were also observed in children congenitally exposed to HIV compared with controls, even among those children with CD4/CD8 ratios greater than 1.0, who therefore had possibly escaped infection. Immune changes in children should be interpreted with caution.