Plasmacytoid dendritic cell (P-DC) precursors in peripheral blood produce large amounts of interferon (IFN)-alpha/beta when triggered by viruses. However, when incubated with interleukin-3 and CD40 ligand, the same precursors differentiate into mature DCs that stimulate naïve CD4(+) T cells to produce Th2 cytokines. We recently reported that P-DCs accumulate in nasal mucosa of experimentally induced allergic rhinitis, supporting a role for this DC subset in Th2-dominated inflammation. Here we examined whether P-DCs accumulate in cutaneous lesions of lupus erythematosus (LE), a disorder associated with increased IFN-alpha/beta production. Our results showed that P-DCs were present in 14 out of 15 tissue specimens of cutaneous LE lesions, but not in normal skin. Importantly, the density of P-DCs in affected skin correlated well (r(s) = 0.79,P < 0.0005) with the high number of cells expressing the IFN-alpha/beta-inducible protein MxA, suggesting that P-DCs produce IFN-alpha/beta locally. Accumulation of P-DCs coincided also with the expression of L-selectin ligand peripheral lymph node addressin on dermal vascular endothelium, adding further support to the notion that these adhesion molecules are important in P-DC extravasation to peripheral tissue sites. Together, our findings suggested that P-DCs are an important source of IFN-alpha/beta in cutaneous LE lesions and may therefore be of pathogenic importance.

Recent evidence suggests that the previously enigmatic cell type designated plasmacytoid monocytes can function as dendritic cells and contribute substantially to both innate and adaptive immunity. This cell type has previously been described only in bone marrow, blood, and organized lymphoid tissue, but not at effector sites with direct Ag exposure such as the mucosae. Plasmacytoid dendritic cells (P-DCs) matured in vitro can induce T cells to produce allergy-promoting Th2 cytokines; therefore, their possible occurrence in nasal mucosa during experimentally elicited allergic rhinitis was examined. Patients with silent nasal allergy were challenged topically with relevant allergen daily for 7 days. Biopsy specimens as well as blood samples were obtained before and during such provocation, and P-DCs were identified by their high expression of CD123 (IL-3R α-chain), together with CD45RA. Our results showed that P-DCs were present in low and variable numbers in normal nasal mucosa but increased dramatically during the allergic reaction. This accumulation concurred with the expression of the L-selectin ligand peripheral lymph node addressin on the mucosal vascular endothelium. The latter observation was particularly interesting in view of the high levels of L-selectin on circulating P-DC precursors and of previous reports suggesting that these cells can enter organized lymphoid tissue via high endothelial venules (which express peripheral lymph node addressin constitutively). Together, our findings suggested that P-DCs are involved in the triggering of airway allergy and that they are directed to allergic lesions by adhesion molecules that normally mediate leukocyte extravasation in organized lymphoid tissue.

No abstract

Ca2؉ entry through the capacitative (store-regulated) pathway was shown to be inhibited in neutrophil granulocytes by the protein kinase C activator phorbol 12-myristate 13-acetate and the chemoattractant N-formylmethionyl-leucyl-phenylalanine (fMLP) by a hitherto unknown mechanism. Measuring both Ca 2؉ and Mn production.

IntroductionHuman cytomegalovirus (HCMV) infection represents a major clinical problem in immunocompromised persons, including transplant recipients and AIDS patients. Prevalence of HCMV seropositivity ranges between 50% and 90% in healthy adults; after primary infection, the virus establishes lifelong latency in the host. 1 Usually, CMV in immunocompromised patients is caused by the reactivation of latent virus. A number of studies have suggested that the virus may aggravate immunodeficiency by interfering with antigen presentation. [2][3][4][5][6][7] In these publications, dendritic cells (DCs) have been generated from monocytes or CD34 ϩ bone marrow progenitor cells after 5 to 12 days of cytokine-supplemented culture. Such monocyte-derived DCs (moDCs) or bone marrowderived Langerhans cells are highly potent stimulators of T-cell activation. Exposure of these DCs to HCMV leads to functional paralysis of the cells, causing impaired T-cell activation. [2][3][4][5][6][7] Several mechanisms for this immunosuppression have been suggested. First, major histocompatibility complex (MHC) class I and class II and costimulatory molecules are down-regulated, resulting in impaired antigen presentation and increased susceptibility to natural killer cell-mediated lysis. [2][3][4][5][6][7][8] Second, a virally induced, soluble immunosuppressive factor released by mature moDCs has been postulated by several groups and was recently identified as CD83. 5,7 Third, infection of immature moDCs is lytic and leads to cell death. 7 Studies of HCMV effects on moDCs and Langerhans cells have shed light on mechanisms for viral immune evasion. However, the results showing paralysis of antigen presentation also raise questions as to how HCMV can be so effectively controlled in the immunocompetent host. Most primary infections induce minimal symptoms, and there is no clear evidence for clinically relevant immunosuppression. 1 Reactivation of the latent virus is believed to happen frequently, 9,10 but it proceeds asymptomatically in a healthy host, indicating a successful immune response. Indeed, an impressively large part of the T-cell repertoire is HCMV specific in seropositive persons. Labeling with MHC class I tetramers in complex with HCMV peptides has shown that 1% to 4% of all CD8 ϩ T cells are specific for HCMV proteins. 11,12 In view of the low pathogenicity of HCMV in immunocompetent persons, paralysis of key antigen-presenting cells by the virus seems unlikely.Elegant studies in mice have elucidated mechanisms for successful immunity to murine CMV (MCMV). 13 After injection of virus into mice, a small subset of DCs, termed plasmacytoid dendritic cells (PDCs), produce high levels of IFN-␣, IL-12, and TNF-␣. The rapid innate response is followed by maturation of several welldefined DC subsets in the mouse spleen and initiation of a strong MCMV-directed T-cell response. Frequencies of infected DCs were generally low and were restricted to a subset expressing CD8␣. These results show a high degree of specialization between murine DCs ...

No abstract

Our results suggest that TSLP-mediated activation of human nasal mucosal CD1c(+) DCs triggers CCR7-dependent migration to the draining lymph nodes and enhances their capacity to initiate TH2 responses. However, the observation that TH2 cytokines abrogate the induction of CCR7 implies that during a TH2-mediated inflammatory reaction, TLSP-activated CD1c(+) DCs are retained in the inflamed tissue to further exacerbate local inflammation by activating local antigen-specific memory TH2 cells.

Background-English-speaking children with specific language impairment (SLI) perform more poorly than their typically developing peers in verbal working memory tasks where processing and storage are simultaneously required. Hungarian is a language with a relatively free word order and a rich agglutinative morphology.