Skin infiltration of CD56bright CD16- natural killer cells in a case of X-SCID with Omenn syndrome-like manifestations

We observed a patient with X-linked severe combined immunodeficiency (X-SCID) with Omenn syndrome-like manifestations. X-linked inheritance, absence of CD132 expression and impaired response to interleukin-2 (IL-2) indicated that the case is typical of X-SCID due to gamma. defect. However, this case was unusual in that circulating natural killer (NK) cells were increased and nearly half of these NK cells exhibited the CD56(bright) CD16(-) phenotype. A missense mutation was found within exon 5 of the IL2RG gene. The identical mutation was detected within NK, CD4(+) T and B cells. Engraftment of maternally derived NK cells or gene reversion was ruled out. The erythroderma-like skin lesion was characterized by infiltration of the dermis by CD56(bright) NK cells admixed with CD1a(+) dendritic cells (DC). Expression of mRNA for inflammatory cytokines was significantly enhanced within the skin. This may be the first human case to demonstrate that close cell-to-cell contact between DC and NK cells provides an effective alternative pathway for NK cell differentiation/activation in vivo.