A BOY WITH X-LINKED HYPER-IGM SYNDROME AND NATURAL-KILLER-CELL DEFICIENCY

We present a boy with hyper-IgM syndrome with a previously not reporte d mutation in the CD40 ligand gene. He also had a concomitant natural killer (NK) cell deficiency. He had no CD56(+) or CD16(+) cells and no NK activity as determined in 4h chromium release cytotoxicity assay. After 5 days in culture with IL-2-containing medium, however, his peri pheral blood mononuclear cells lysed both NK-sensitive and NK-resistan t targets, showing that he had lymphokine-activated killer cell precur sors in the circulation. Due to the associated neutropenia, he was tre ated with granulocyte colony-stimulating factor (G-CSF) and responded well. In the same period we observed a transient increase in the numbe r of NK cells, Isolated NK cell deficiencies an extremely rare. We sug gest that the defect in our patient is part of the hyper-IgM syndrome, probably representing the phenotype of the new mutation described. Th us, it is possible that both the neutropenia and the NK cell deficienc y are due to lack of growth-promoting signals normally delivered by th e CD40 ligand.