Expansion of CD3+CD4-CD8- T cell population expressing high levels of IL-5 in Omenn's syndrome.

Omenn's syndrome is a fatal, autosomal-recessive combined immune deficiency characterized by several erythematous exfoliative eruptions, lymphadenopathy, hepatosplenomegaly, and elevated eosinophil count. In some of these patients an expansion of CD3+CD4-CD8- double negative (DN) T cell population was observed. We show here that the DN population represents a clonal expansion of T cells which preferentially use V beta 14 in their T cell receptor complex. Using polymerase chain reaction, we show that patient's DN cells express spontaneously high levels of IL-5, thus possibly explaining the abundance of eosinophils in this disorder. The increase of IgE observed in patients with Omenn's syndrome is unlikely to be related to IL-4 production, as IL-4 levels in patient samples were low. However, patient's low expression of interferon-gamma (IFN-gamma), which has been reported to inhibit IgE production, may explain the elevated levels of IgE in this patient. The results thus highlight the importance of the inhibitory effect of IFN-gamma on regulation of IgE production.