In vivo interferon-gamma induced changes in gene expression dramatically alter neutrophil phenotype.

The cytokine Interferon-γ (IFN-γ) exerts powerful immunoregulatory effects on the adaptive immune system and also enhances functions of the neutrophil (PMN). The clinical use of IFN-γ has been driven by the finding that its administration to patients with chronic granulomatous disease (CGD) results in decreased incidence and severity of infections. However, IFN-γ has no effect on the characteristic defect of CGD, the inability to convert oxygen to microbicidal metabolites including superoxide anion (O2-) during the phagocytosis associated oxidative burst. We administered varying doses of IFN-γ to adult volunteers and studied the effects on plasma drug levels and response molecules and PMNs isolated from blood drawn at intervals over a 96- hour period. Plasma concentrations of IFN-γ, IP-10 and neopterin, and stimulated release of O2- from PMNs exhibited dose- and time-dependent increases after IFN-γ administration. Gene expression in PMNs was altered for 2775 genes; changes occurred rapidly after administration and returned to baseline in 24-36 hours. Several genes involved with neutrophil host defense were upregulated including those for components of the O2- generating NADPH oxidase; innate-immune and Fc receptors; proteins involved in MHCI and II; a regulator of circulating PMN number; guanylate binding proteins; and a key enzyme in synthesis of an essential NOS cofactor. Coordinate changes were detected in protein levels of representative products from several of these genes. Lysates from isolated neutrophils also demonstrated a spike in NO following IFN-γ administration. IFN-γ appears to increase non-oxygen dependent microbicidal functions of PMNs which could provide strategies to compensate for deficiencies, explain its clinical benefit for CGD patients and expand therapeutic applications of IFN-γ to other disorders. Trial registration: Protocol registered in ClinicalTrials.gov, NCT02609932, Effect of IFN-γ on Innate Immune Cells.

Metabolic abnormalities in G6PC3-deficient human neutrophils result in severe functional defects.

Severe congenital neutropenia type 4 (SCN-4) is an autosomal recessive condition in which mutations in the G6PC3 gene encoding for the catalytic 3 subunit of glucose-6-phosphatase-ß result in neutropenia, neutrophil dysfunction, and other syndromic features. We report a child with SCN-4 caused by compound heterozygous mutations in G6PC3, a previously identified missense mutation in exon 6 (c.758G>A[p.R235H]), and a novel missense mutation in exon 2 (c.325G>A[p.G109S]). The patient had recurrent bacterial infections, inflammatory bowel disease, neutropenia, and intermittent thrombocytopenia. Administration of granulocyte colony-stimulating factor (G-CSF) resolved the neutropenia and allowed for detailed evaluation of human neutrophil function. Random and directed migration by the patient's neutrophils was severely diminished. Associated with this were defects in CD11b expression and F-actin assembly. Bactericidal activity at bacteria/neutrophil ratios >1:1 was also diminished and was associated with attenuated ingestion. Superoxide anion generation was <25% of control values, but phox proteins appeared quantitatively normal. Extensive metabolomics analysis at steady state and upon incubation with stable isotope-labeled tracers (U-13C-glucose, 13C,15N-glutamine, and U-13C-fructose) demonstrated dramatic impairments in early glycolysis (hexose phosphate levels), hexosemonophosphate shunt (required for the generation of the NADPH), and the total adenylate pool, which could explain the dramatic cell dysfunction displayed by the patient's neutrophils. Preliminary experiments with fructose supplementation to bypass the enzyme block demonstrated that the metabolic profile could be reversed, but was not sustained long enough for functional improvement. In human deficiency of G6PC3, metabolic defects resulting from the enzyme deficiency account for diverse neutrophil functional defects and present a major risk of infection.

Parents' perceptions of skin cancer threat and children's physical activity.

INTRODUCTION: Sun exposure is a major risk factor for skin cancer, but without physical activity, children are at risk of childhood obesity. The objective of this study was to explore relationships between parental perceptions of skin cancer threat, sun protection behaviors, physical activity, and body mass index (BMI) in children. METHODS: This is a cross-sectional analysis nested within the Colorado Kids Sun Care Program sun safety intervention trial. In summer 2007, parent telephone interviews provided data on demographics, perceptions of skin cancer threat, sun protection behaviors, and physical activity. Physical examinations provided data on phenotype, freckling, and BMI. Data from 999 Colorado children born in 1998 were included in analysis. We used analysis of variance, Spearman's rho (ρ) correlation, and multivariable linear regression analysis to evaluate relationships with total amount of outdoor physical activity. RESULTS: After controlling for sex, race/ethnicity, skin color, and sun protection, regression analysis showed that each unit increase in perceived severity of nonmelanoma skin cancer was associated with a 30% increase in hours of outdoor physical activity (P = .005). Hours of outdoor physical activity were not related to perceived severity of melanoma or perceived susceptibility to skin cancer. BMI-for-age was not significantly correlated with perceptions of skin cancer threat, use of sun protection, or level of physical activity. CONCLUSION: The promotion of sun safety is not likely to inhibit physical activity. Skin cancer prevention programs should continue to promote midday sun avoidance and sun protection during outdoor activities.