SERUM IGD LEVELS IN CHILDREN UNDER INVESTIGATION FOR AND WITH DEFINEDIMMUNODEFICIENCY

Background: The function and regulation of circulating IgD are unclear , Serum IgD levels were increased in a wide range of immunological dis eases but these associations did not give a clue to the regulation of serum IgD production. Methods: Serum IgD levels in 131 children with v arious non-HIV-related immunodeficiency diseases were investigated to examine their relationship with immunoglobulin or antibody production and activation of the immune system, Data from a group of 109 nonimmun odeficient children were also available for comparison. Results: There was a bimodal distribution of serum IgD levels. In 87 patients IgD le vels fell below the limit of detection of 5 IU/ml, while the remainder showed an approximately normal distribution skewed to the right after log transformation. The proportion of children with undetectable IgD levels (< 5 IU/ml) was significantly increased in immunodeficient chil dren (87/131 vs. 28/109, p < 0.001). No difference in the occurrence o f immunoglobulin or antibody deficiencies was demonstrated in immunode ficient children with detectable and nondetectable IgD levels. There w as a positive correlation of serum IgD with age, serum IgA and IgE, wh ite blood count and CD4+CD25+ lymphocytes but not with other immunoglo bulin isotypes or immune activation markers. Conclusion: Determination of serum IgD levels did not seem to be of particular clinical benefit in the investigation of HIV-negative immunodeficient children and ser um IgD levels were not associated with the general picture of immune a ctivation. Observed distribution patterns and associations may have im plications for the regulation of serum IgD production.