Immune cell phenotype and functional defects in Netherton syndrome.

Netherton syndrome (NS) is a rare life-threatening syndrome caused by SPINK5 mutations leading to a skin barrier defect and a severe atopic diathesis. NS patients are prone to bacterial infections, but the understanding of the underlying immune deficiency is incomplete. We analyzed blood lymphocyte phenotypes and function in relation to clinical infections in 11 Finnish NS patients, aged 3 to 17 years, and healthy age-matched controls. The proportion of B cells (CD19+) and naïve B cells (CD27-, IgD+) were high while memory B cells (CD27+) and switched memory B cells (CD27+IgM-IgD-), crucial for the secondary response to pathogens, was below or in the lowest quartile of the reference values in 8/11 (73%) and 9/11 (82%) patients, respectively. The proportion of activated non-differentiated B cells (CD21low, CD38low) was below or in the lowest quartile of the reference values in 10/11 (91%) patients. Despite normal T cell counts, the proportion of naïve CD4+ T cells was reduced significantly and the proportion of CD8+ T central memory significantly elevated. An increased proportion of CD57+ CD8+ T cells indicated increased differentiation potential of the T cells. The proportion of cytotoxic NK cells was elevated in NS patients in phenotypic analysis based on CD56DIM, CD16+ and CD27- NK cells but in functional analysis, decreased expression of CD107a/b indicated impaired cytotoxicity. The T and NK cell phenotype seen in NS patients also significantly differed from that of age-matched atopic dermatitis (AD) patients, indicating a distinctive profile in NS. The frequency of skin infections correlated with the proportion of CD62L+ T cells, naïve CD4+ and CD27+ CD8+ T cells and with activated B cells. Clinically beneficial intravenous immunoglobulin therapy (IVIG) increased naïve T cells and terminal differentiated effector memory CD8+ cells and decreased the proportion of activated B cells and plasmablasts in three patients studied. This study shows novel quantitative and functional aberrations in several lymphocyte subpopulations, which correlate with the frequency of infections in patients with Netherton syndrome. IVIG therapy normalized some dysbalancies and was clinically beneficial.