Th1?Th2 Interaction: Is More Complex than a See-saw?

Organization of the Skin Immune System and Compartmentalized Immune Responses in Infectious Diseases

The skin is an organ harboring several types of immune cells that participate in innate and adaptive immune responses. The immune system of the skin comprises both skin cells and professional immune cells that together constitute what is designated skin-associated lymphoid tissue (SALT). In this review, I extensively discuss the organization of SALT and the mechanisms involved in its responses to infectious diseases of the skin and mucosa. The nature of these SALT responses, and the cellular mediators involved, often determines the clinical course of such infections. I list and describe the components of innate immunity, such as the roles of the keratinocyte barrier and of inflammatory and natural killer cells. I also examine the mechanisms involved in adaptive immune responses, with emphasis on new cytokine profiles, and the role of cell death phenomena in host-pathogen interactions and control of the immune responses to infectious agents. Finally, I highlight the importance of studying SALT in order to better understand host-pathogen relationships involving the skin and detail future directions in the immunological investigation of this organ, especially in light of recent findings regarding the skin immune system.

Sceptridium ternatum attenuates allergic contact dermatitis-like skin lesions by inhibiting T helper 2-type immune responses and inflammatory responses in a mouse model

BACKGROUND

Sceptridium ternatum (ST) is a medicinal herb used in folk remedies for the treatment of various disorders such as pertussis, allergic asthma, abdominalgia, diarrhea, and external use for wound healing. However, the biological and pharmacological activities of ST are not fully clarified besides anti-asthmatic effect.

OBJECTIVE

We studied a Sceptridium ternatum ethanol extract (ST) with respect to its anti-inflammatory and immune regulatory activities in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, concanavalin A (conA)-stimulated BALB/c mice splenocytes, and a 2,4-dinitrochlorobenzene (DNCB)-induced allergic contact dermatitis (ACD) mouse model.

METHODS

RAW 264.7 cells were pretreated with ST for 1h and then stimulated with LPS. To determine the anti-inflammatory effects of ST, the production of nitric oxide (NO), interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) were measured using an enzyme-linked immunosorbent assay (ELISA). To determine its anti-allergic effects, splenocytes from BALB/c mice were incubated and stimulated with conA in the absence or presence of ST for 48h. The production of IL-4 and interferon (IFN)-γ in culture supernatants were evaluated by ELISA. To test the effects of ST on ACD, 100μL of 1% DNCB was applied to the dorsal skin of BALB/c mice for 2 weeks, and ST was administered 2 h before DNCB application. The thicknesses of the epidermis and dermis were determined by skin histological analysis. Serum immunoglobulin (Ig) E levels, the production of IL-1β, IL-4, and IL-6 in dorsal skin tissue, and T helper (Th) 2 cytokines production of CD4(+) T cells were analyzed by ELISA. The expression of nuclear transcription factor-κB (NF-κB) both in vitro and in vivo was determined via immunoblotting.

RESULTS

In RAW 264.7 cells, ST inhibited LPS-induced inflammation mediator production and NF-κB expression. ST upregulated IFN-γ production and downregulated IL-4 production in conA-stimulated splenocytes. ST application reduced the thicknesses of the epidermis and dermis by decreasing serum IgE level and the expressions of IL-1β, IL-4, IL-6, and NF-κB in the dorsal skin of the DNCB-induced ACD model mice. Furthermore, ST treated group showed reduction of the Th2 cytokines production in activated CD4(+) T cells.

CONCLUSION

These findings not only indicate that application of ST reduced skin thickening by regulating Th 2-type allergic responses and inhibiting expression of inflammatory mediators in a DNCB-induced ACD mouse model, but also suggest that Sceptridium ternatum is a natural option for the treatment of skin inflammation.

Phosphatidylinositol-3-kinase activity during in vitro dendritic cell generation determines suppressive or stimulatory capacity

Modulating PI3K at different stages of dendritic cells (DC) generation could be a novel means to balance the generation of immunosuppressive versus immunostimulatory DC. We show that PI3K inhibition during mouse DC generation in vitro results in cells that are potently immunosuppressive and characteristic of CD8alpha- CD11c+ CD11b+ DC. These DC exhibited low surface class I and class II MHC, CD40, and CD86 and did not produce TNF-alpha. In allogeneic MLR, these DC were suppressive. Although in these mixed cultures, there was no increase in the frequency of CD4+ CD25+ Foxp3+ cells, the Foxp3 content on a per cell basis was significantly increased. Sustained TLR9 signaling in the presence of PI3K inhibition during DC generation overrode the cells' suppressive phenotype.

New insight into immunity and immunopathology of Rickettsial diseases

Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecular Rickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered.

Comparative study and expression analysis of the interferon gamma gene locus cytokines in Xenopus tropicalis

Using bioinformatics approach, the genome locus containing interleukin (IL)-22, IL-26, and interferon gamma (IFN-gamma) genes has been identified in the amphibian, Xenopus tropicalis. Like that in other vertebrates such as fish, birds, and mammals, the Xenopus IL-22, IL-26, and IFN-gamma are clustered in the same chromosome and the adjacent genes are conserved. The genomic structures of the Xenopus IL-22, IL-26, and IFN-gamma gene were identical to that of their mammalian counterparts. The Xenopus IL-22 and IL-26 genes contained five exons and four introns while the Xenopus IFN-gamma gene consisted of four exons and three introns. The Xenopus IL-22, IL-26, and IFN-gamma share 14.1-41.6%, 14.6-31.2%, and 23.7-36.5% identity to their counterparts in other species, respectively. Reverse-transcription polymerase chain reaction (PCR) and real-time quantitative PCR analyses revealed that the expression of IL-22, IL-26, and IFN-gamma genes was significantly upregulated after simulation with bacterial polyliposaccharide and/or synthetic double-stranded poly(I:C), suggesting these cytokines like those in other vertebrates play an important role in regulating immune response in Xenopus.

Does the Atopic Phenotype Prevent Development of Active Tuberculosis Infection?

This study investigated the relationship between the atopic phenotype and the development of active tuberculosis. A total of 82 human immunodeficiency virus-negative males with active pulmonary tuberculosis and 88 healthy controls were enrolled into this prospective study. Serum immunoglobulin E (IgE) levels were measured and skin prick tests performed before initiation of treatment. Skin prick tests were positive in 34.1% of the tuberculosis patients and 39.8% of the controls. Allergic respiratory symptoms were significantly less frequent in skin prick test positive tuberculosis patients (21.4%) compared with skin prick test positive controls (62.9%). Median IgE levels in atopic tuberculosis patients were significantly higher than in atopic controls. The low rate of atopic respiratory complaints seen in the tuberculosis patients, despite having similar allergic skin prick test sensitivities to the controls, could be attributed to a weak T-helper (Th) 2 immune reaction and its effects on Th1–Th2 interaction.