EXPANSION OF CD3(-)CD8(-) T-CELL POPULATION EXPRESSING HIGH-LEVELS OFIL-5 IN OMENNS SYNDROME()CD4()

Omenn's syndrome is a fatal, autosomal-recessive combined immune defic iency characterized by several erythematous exfoliative eruptions, lym phadenopathy, hepatosplenomegaly, and elevated eosinophil count. In so me of these patients an expansion of CD3(+)CD4(-)CD8(-) double negativ e (DN) T cell population was observed. We show here that the DN popula tion represents a clonal expansion of T cells which preferentially use V beta 14 in their T cell receptor complex. Using polymerase chain re action, we show that patient's DN cells express spontaneously high lev els ofIL-5, thus possibly explaining the abundance of eosinophils in t his disorder. The increase of IgE observed in patients with Omenn's sy ndrome is unlikely to be related to IL-4 production, as IL-4 levels in patient samples were low. However, patient's low expression of interf eron-gamma (IFN-gamma), which has been reported to inhibit IgE product ion, may explain the elevated levels of IgE in this patient. The resul ts thus highlight the importance of the inhibitory effect of IFN-gamma on regulation of IgE production.