Altered natural killer cell subset distributions in resolved and persistent hepatitis C virus infection following single source exposure

BACKGROUND

Natural killer (NK) cells may be impaired in patients with persistent hepatitis C virus (HCV) infection, but studies to date have yielded inconsistent findings due to patient and virus heterogeneity and difficulties obtaining appropriate controls.

AIMS

To overcome these variables, we have examined numbers, phenotypes, cytotoxic activities and cytokine profiles of circulating NK cells from Irish women who acquired infection through administration of HCV genotype 1b-contaminated anti-D immunoglobulin from a single source and matched controls.

RESULTS

Comparing 29 women who developed persistent infection with 21 who spontaneously resolved infection and 26 controls, we found that NK cell numbers were consistently lower in the persistently infected group (p = 0.02 and 0.002). This decrease was due to depletions of NK cells expressing low levels of CD56 (CD56(dim) NK cells; p = 0.004 and 0.0001), whilst CD56(bright) NK cells were expanded (p = 0.004 and 0.0001). Compared to HCV resolvers, CD56(dim) NK cells from persistently infected patients less frequently expressed CD16 and more frequently expressed NKG2A/C/E. These phenotypic changes did not significantly affect natural or interleukin-2-induced cytotoxicity by peripheral blood mononuclear cells against K562 and Daudi targets. Greater frequencies of CD56(bright) NK cells from chronic HCV patients produced interferon-gamma compared with HCV responders (p = 0.05) and controls (p = 0.0001) after phorbol ester stimulation in vitro.

CONCLUSIONS

Alterations in NK subset distributions in chronic HCV infection may explain why previous reports of impaired NK cell functions were difficult to confirm. Altered NK cell functions may contribute to impaired cellular immune responses and chronicity of disease following HCV infection.

Protection against Bordetella pertussis infection following parenteral or oral immunization with antigens entrapped in biodegradable particles: effect of formulation and route of immunization on induction of Th1 and Th2 cells

The immunogenicity and protective efficacy of systemically and orally delivered pertussis antigens entrapped in either microparticle poly-lactide-co-glycolide (PLG) or nanoparticle PLG formulations were evaluated in a murine respiratory challenge model for infection with Bordetella pertussis. The results demonstrate that immunization with two parenteral doses of 1 microg or three oral doses of 100 microg of pertussis toxoid (PTd) and filamentous haemagglutinin (FHA) encapsulated in PLG conferred a high level of protection against B. pertussis challenge. Furthermore protection could be generated with a single parenteral immunization with a combined microparticle and nanoparticle formulation. However, the route of immunization and the size of the particles affected the type of T cell response induced. Parenteral immunization with PTd and FHA entrapped in PLG microparticles elicits a potent type 1 T cell response and potent antibody response when given by the intraperitoneal (i.p.) or intramuscular (i.m.) route. In contrast, nanoparticle formulations favoured the induction of Th2 cells.

Factors produced by activated leukocytes alter renal epithelial cell differentiation

The development of tubulointerstitial fibrosis in inflammatory renal diseases has been linked to disease progression to end-stage renal failure. Understanding the interactions of the factors influencing inflammation and activating the fibrotic process, that is, the inflammatory infiltrate and the resident proximal tubular cells, may lead to a determination of the mechanisms that regulate tubulointerstitial fibrosis. We used an in vitro model of human proximal tubule cells that were stimulated with supernatant from activated peripheral blood mononuclear cells (leukocytes) to study the alterations in cellular phenotype, and examined the signaling pathways mediating epithelial-fibroblast like transdifferentiation. Our hypothesis of the proposed sequence of events leading to tubulointerstitial fibrosis is explained.

The human liver contains multiple populations of NK cells, T cells, and CD3+CD56+ natural T cells with distinct cytotoxic activities and Th1, Th2, and Th0 cytokine secretion patterns

The human liver contains significant numbers of T cells, NK cells, and lymphocytes that coexpress T and NK cell receptors. To evaluate their functional activities, we have compared the cytotoxic activities and cytokines produced by normal adult hepatic CD3+CD56- (T) cells, CD3-CD56+ (NK) cells, and CD3+CD56+ (natural T (NT)) cells. In cytotoxicity assays using immunomagnetic bead-purified NK cell, T cell, and NT cell subpopulations as effectors, fresh hepatic NK cells lysed K562 targets, while NT cells could be induced to do so by culturing with IL-2. Both NT and T cells were capable of redirected cytolysis of P815 cells using Abs to CD3. Flow cytometric analysis of cytokine production by fresh hepatic lymphocyte subsets activated by CD3 cross-linking or PMA and ionomycin stimulation indicated that NT cells and T cells could produce IFN-gamma, TNF-alpha, IL-2, and/or IL-4, but little or no IL-5, while NK cells produced IFN-gamma and/or TNF-alpha only. The majority of NT cells produced inflammatory (Th1) cytokines only; however, approximately 6% of all hepatic T cells, which included 5% of Valpha24 TCR-bearing NT cells and 2% of gammadeltaTCR+ cells, simultaneously produced IFN-gamma and IL-4. The existence of such large numbers of cytotoxic lymphocytes with multiple effector functions suggests that the liver is an important site of innate immune responses, early regulation of adaptive immunity, and possibly peripheral deletion of autologous cells.

Human small intestinal epithelial cells secrete interleukin-7 and differentially express two different interleukin-7 mRNA Transcripts: implications for extrathymic T-cell differentiation

The small intestinal epithelium, composed of epithelial cells (EC) and intraepithelial T lymphocytes, is exposed to numerous ingested antigens. Small intestinal EC may act as accessory and/or antigen presenting cells for intestinal T cells, some of which may mature extrathymically and regulate local immunity and tolerance. Since interleukin-7 (IL-7) plays an essential role in T cell maturation and activation, we examined its expression by human small intestinal EC. IL-7 was detected by ELISA in supernatants from 4 of 4 epithelial layer (EpL) cultures. Using RT-PCR, IL-7 mRNA was detected in 4 EpL studied, and two distinct IL-7 transcripts were identified in 3 of the 4. The ratios of the intensities of the larger to the smaller bands varied amongst individuals. Furthermore, the intensity ratios were higher in whole-thickness intestine and lamina propria preparations than in their corresponding EpL. This is the first report of the expression of two IL-7 transcripts in human intestine and of IL-7 secretion by human small intestinal EpL cells. This supports the hypothesis that small intestinal EC may influence differentiation and/or activation of neighboring T cells. The differential expression of the two transcripts may have important implications for immune regulation in the intestinal epithelium.