Natural-killer-cell activity in atopic dermatitis

Association of KIR Genes and MHC Class I Ligands with Atopic Dermatitis

Atopic dermatitis (AD) is a chronic illness that is associated with immune dysregulation. NK cell function has previously been associated with AD. NK cells directly interact with polymorphic HLA class I ligand variants using killer cell Ig-like receptors (KIRs). The purpose of this study was to identify potential associations between NK cell function and AD by evaluating variation in the presence of KIR genes as well as KIR gene interactions with the appropriate HLA class I KIR-specific ligands. Human DNA from the genetics of AD case-control study was used to genotype HLA class I KIR-specific ligands and the presence of KIR genes. In the full cohort, an increased risk of AD was noted for KIR2DL5 (1.51 [1.13, 2.01]), KIR2DS5 (1.72 [1.26, 2.34]), and KIR2DS1 (1.41 [1.04, 1.91]). Individuals with KIR2DS5 or KIR2DS1 and the HLA-C*C2 epitope were at an increased risk of AD (1.74 [1.21, 2.51] and 1.48 [1.04, 2.12], respectively). The HLA-B*-21T (TT) leader sequence increased the risk of AD across ethnicity. African Americans with KIR2DL2, KIR2DS1, KIR2DL5, and KIR2DS5 are more likely to have AD, and the risk increased for KIR2DS1 and KIR2DS5 in the presence of appropriate HLA-C C2 epitope. The risk of AD also increased for individuals with the HLA-B*-21T leader sequence. Future studies should focus on KIR gene allelic variation as well as consider cell-based measurements of KIR and the associated HLA class I epitopes.

Defective natural killer cell activity in a mouse model of eczema herpeticum

BACKGROUND

Patients with atopic dermatitis (AD) are susceptible to several viruses, including herpes simplex virus (HSV). Some patients experience 1 or more episodes of a severe skin infection caused by HSV termed eczema herpeticum (EH). There are numerous mouse models of AD, but no established model exists for EH.

OBJECTIVE

We sought to establish and characterize a mouse model of EH.

METHODS

We infected AD-like skin lesions with HSV1 to induce severe skin lesions in a dermatitis-prone mouse strain of NC/Nga. Gene expression was investigated by using a microarray and quantitative PCR; antibody titers were measured by means of ELISA; and natural killer (NK) cell, cytotoxic T-cell, regulatory T-cell, and follicular helper T-cell populations were evaluated by using flow cytometry. The role of NK cells in HSV1-induced development of severe skin lesions was examined by means of depletion and adoptive transfer.

RESULTS

Inoculation of HSV1 induced severe erosive skin lesions in eczematous mice, which had an impaired skin barrier, but milder lesions in small numbers of normal mice. Eczematous mice exhibited lower NK cell activity but similar cytotoxic T-cell activity and humoral immune responses compared with normal mice. The role of NK cells in controlling HSV1-induced skin lesions was demonstrated by experiments depleting or transferring NK cells.

CONCLUSION

A murine model of EH with an impaired skin barrier was established in this study. We demonstrated a critical role of defective NK activities in the development of HSV1-induced severe skin lesions in eczematous mice.

Smallpox vaccine safety is dependent on T cells and not B cells

The licensed smallpox vaccine, ACAM2000, is a cell culture derivative of Dryvax. Both ACAM2000 and Dryvax are administered by skin scarification and can cause progressive vaccinia, with skin lesions that disseminate to distal sites. We have investigated the immunologic basis of the containment of vaccinia in the skin with the goal to identify safer vaccines for smallpox. Macaques were depleted systemically of T or B cells and vaccinated with either Dryvax or an attenuated vaccinia vaccine, LC16m8. B cell depletion did not affect the size of skin lesions induced by either vaccine. However, while depletion of both CD4(+) and CD8(+) T cells had no adverse effects on LC16m8-vaccinated animals, it caused progressive vaccinia in macaques immunized with Dryvax. As both Dryvax and LC16m8 vaccines protect healthy macaques from a lethal monkeypox intravenous challenge, our data identify LC16m8 as a safer and effective alternative to ACAM2000 and Dryvax vaccines for immunocompromised individuals.

Characteristics of atopic children with pandemic H1N1 influenza viral infection: pandemic H1N1 influenza reveals 'occult' asthma of childhood

The number of human cases of pandemic H1N1 influenza viral infection has increased in Japan since April 2009, as it has worldwide. This virus is widespread in the Yamaguchi prefecture in western Japan, where most infected children exhibited respiratory symptoms. Bronchial asthma is thought to be one of the risk factors that exacerbate respiratory symptoms of pandemic H1N1-infected patients, but the pathogenesis remains unclear. We retrospectively investigated the records of 33 children with pandemic H1N1 influenza viral infection who were admitted to our hospital between October and December 2009 and analyzed their clinical features. The percentage of children with asthma attack, with or without abnormal findings on chest radiographs (pneumonia, atelectasis, etc.), caused by pandemic H1N1 influenza infection was significantly higher than that of children with asthma attack and 2008-2009 seasonal influenza infection. Of the 33 children in our study, 22 (66.7%) experienced an asthma attack. Among these children, 20 (90.9%) did not receive long-term management for bronchial asthma, whereas 7 (31.8%) were not diagnosed with bronchial asthma and had experienced their first asthma attack. However, the severity of the attack did not correlate with the severity of the pulmonary complications of pandemic H1N1 influenza viral infection. The pandemic H1N1 influenza virus greatly increases the risk of lower respiratory tract complications such as asthma attack, pneumonia, and atelectasis, when compared to the seasonal influenza virus. Furthermore, our results suggest that pandemic H1N1 influenza viral infection can easily induce a severe asthma attack, pneumonia, and atelectasis in atopic children without any history of either an asthma attack or asthma treatment.

Inhibition of NK cell activity by IL-17 allows vaccinia virus to induce severe skin lesions in a mouse model of eczema vaccinatum

Threats of bioterrorism have renewed efforts to better understand poxvirus pathogenesis and to develop a safer vaccine against smallpox. Individuals with atopic dermatitis are excluded from smallpox vaccination because of their propensity to develop eczema vaccinatum, a disseminated vaccinia virus (VACV) infection. To study the underlying mechanism of the vulnerability of atopic dermatitis patients to VACV infection, we developed a mouse model of eczema vaccinatum. Virus infection of eczematous skin induced severe primary erosive skin lesions, but not in the skin of healthy mice. Eczematous mice exhibited lower natural killer (NK) cell activity but similar cytotoxic T lymphocyte activity and humoral immune responses. The role of NK cells in controlling VACV-induced skin lesions was demonstrated by experiments depleting or transferring NK cells. The proinflammatory cytokine interleukin (IL)-17 reduced NK cell activity in mice with preexisting dermatitis. Given low NK cell activities and increased IL-17 expression in atopic dermatitis patients, these results can explain the increased susceptibility of atopic dermatitis patients to eczema vaccinatum.

The effect of topical steroid application on natural killer cell activity

Peripheral blood natural killer (NK) cell activity of a group of 10 healthy non-atopic volunteers was reduced following the topical application of 15 g of 0.1% betamethasone valerate ointment to the skin nightly for 1 week. In contrast, no such effect was observed when the inactive base of the steroid ointment was used. NK cell activity dropped significantly by day 7 (P less than 0.05) and then recovered, although NK cell activity at day 22 was still lower than that observed at the start of the experiment. These findings suggest that topically applied steroid is absorbed in sufficient amounts to cause a systemic effect on NK cell function. This may have implications in a number of dermatological disorders, including atopic dermatitis, where topical steroids form the mainstay of treatment.

Natural killer cell function in atopic dermatitis

The natural killer cell activity was studied in 41 children with mild, moderate and severe atopic dermatitis (AD) and in 37 controls. The natural killer cell function of lymphocytes was reduced in atopic children (mean +/- SD 21.92 +/- 6.18% vs. 43.87 +/- 5.80%; p less than 0.0001). This decrease was not related to the IgE serum level. A negative correlation was found between natural killer cell activity and the clinical severity of AD (r = 0.73; p less than 0.001). Natural killer cell function was re-evaluated after 9 months in 27 children during a quiescent phase of AD; it was still low, but to a lesser degree (27.66 +/- 5.42%, in the quiescent phase, vs. 43.87 +/- 5.80, controls; p less than 0.0001). The reduced natural killer cell activity seems related to the disease activity.

Immunophenotyping of the cutaneous infiltrate and of the mononuclear cells in the peripheral blood in patients with atopic dermatitis

Fourteen adult patients with chronic atopic dermatitis and active skin lesions had a skin biopsy and venous blood sample taken on the same day. Absolute numbers of circulating lymphocytes were normal in all patients. Fluorescence-activated cell sorter (FACS) analysis revealed normal numbers of total T lymphocytes and T-helper and T-suppressor subsets (helper:suppressor ratio, 2:1) in the atopic patients' peripheral blood, but an increase in circulating B lymphocytes and in HLA-D-related antigen-bearing cells. The skin biopsy showed a dermal infiltrate of predominantly T-helper lymphocytes (helper:suppressor ratio, 7:1). These cells showed strong HLA-DR plasma membrane staining. There was no HLA-DR staining in the membranes of epidermal keratinocytes. Using a monoclonal antihuman IgE, positive staining was observed in the dermis, though none was identified in the epidermis. The dermal anti-IgE staining was concentrated around clusters of T lymphocytes.

Humoral and cellular immunity in children with active and quiescent atopic dermatitis

Serum immunoglobulins (IgG, IgM, IgA and IgE), C3, and C4, T lymphocyte subsets, neutrophil chemotaxis and natural killer cell-mediated cytotoxic activity were measured in 34 children with atopic dermatitis and 31 healthy controls. Twenty-four patients were re-evaluated when their dermatitis was quiescent. Serum levels of IgG, IgM and IgE were significantly higher in the patients with atopic dermatitis than in the controls, while levels of serum IgA did not differ significantly between the two groups. C3 levels were lower in the patients than in the controls and correlated inversely with clinical disease severity. C4 levels were not significantly altered. Numbers of suppressor/cytotoxic T lymphocytes and polymorphonuclear leukocyte chemotaxis were significantly reduced in the atopic patients. There was a significant inverse correlation between the natural killer cell-mediated cytotoxic activity and the severity and extent of the dermatitis. These results support the hypothesis that atopic dermatitis is connected with a defect in cellular immunity.

Natural killer cell activity in atopic dermatitis: a sequential study

It is well-recognized that patients with atopic dermatitis handle certain cutaneous viral infections poorly. As natural killer (NK) cell activity is considered to contribute to the immune response to viral infection, seven young adults with atopic dermatitis had their NK cell function assessed over a 12-month period. Natural killer cell activity was found to correlate inversely with disease activity. The more active the disease, the greater was the reduction in NK cell function (P less than 0.01. In addition, a strong correlation between clinical activity and IgE was shown (P less than 0.001).