Basophils infiltrate into skin lesions more commonly than previously thought, and thus they may play important roles in a variety of inflammatory skin diseases.
Contact hypersensitivity (CHS) is thought to be mainly associated with the activation of T helper type 1 (Th1) cells. However, there is also evidence that Th2 cells or Th2 cytokines play a role in the development of CHS. To analyze the functional contribution of Th2 cytokines interleukin (IL)-4 and IL-13, signal transducer and activator of transcription 6 (STAT6)-deficient (STAT6−/−) and wild-type (wt) control C57BL/6 mice were contact sensitized with 5% 2,4,6-trinitrochlorobenzene (TNCB), 0.5% 2,4-dinitrofluorobenzene, or 5% 4-ethoxyl methylene-2-phenyl-2-oxazolin-5-one, and any skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6−/− mice compared with wt mice.A histological analysis revealed that the infiltration of both eosinophils and neutrophils in the skin challenged after 24 h in STAT6−/− mice decreased substantially compared with that in wt mice. The expression of Th2 cytokines (IL-4, IL-5) in TNCB-challenged skin tissues and the supernatants from T cells stimulated by 2,4,6-trinitrobenzene sulfonate–modified spleen cells, as well as the immunoglobulin (Ig)E and IgG1 response after challenge, were also profoundly reduced in STAT6−/− mice, whereas the expression of interferon γ was the same in STAT6−/− and wt mice after challenge. Furthermore, adoptive transfer experiments revealed that STAT6−/− mice induced CHS after injection of lymph node cells obtained from sensitized wt mice. Our data suggest that the STAT6 signal plays a critical role in the induction phase of CHS.
The migration of Langerhans cells is an initial event in the sensitization phase of contact sensitivity. Langerhans cells travel from the epidermis to the regional lymph node, and can be variously modulated in the skin where many cytokines are released from epidermal cells, dermal cells, T helper (Th) cells, and other inflammatory cells during the sensitization and elicitation phase of contact dermatitis, and thus induce an altered inflammatory skin reaction. The modulatory effect of the cytokines released in the skin, such as IL-1beta, GM-CSF, and TNF-alpha as epidermal cytokines, IL-2, IL-12, and IFN-gamma as Th1 type cytokines, and IL-4 and IL-10 as Th2 type cytokines, was analyzed using the chemotactic chamber method in this study. Both GM-CSF and TNF-alpha induced the migration of human Langerhans cells in vitro, whereas IL-1beta, IL-2, IL-10, IL-12, and IFN-gamma had no effect on Langerhans cell migration. In contrast, IL-4 inhibited Langerhans cell migration in a dose dependent manner. The inhibitory activity of IL-4 was reversed by both anti-human IL-4 monoclonal antibody and anti-human IL-4 receptor monoclonal antibody. IL-4 inhibited the Langerhans cell migration induced by both TNF-alpha and GM-CSF. Furthermore, anti-TNF-RII monoclonal antibody inhibited both random migration and the migration induced by TNF-alpha, but not that induced by GM-CSF. A reverse-transcriptase-polymerase chain reaction and fluorescence-activated cell sorter analysis revealed that TNF-alpha up-regulated and IL-4 downregulated the TNF receptor II (TNF-RII) expression of Langerhans cells at both the mRNA and the protein levels. The pretreatment of Langerhans cells with TNF-alpha enhanced the migration of Langerhans cells and the expression of TNF-RII. After pretreating Langerhans cells with TNF-alpha, IL-4 inhibited both the migration of Langerhans cells and the expression of TNF-RII in a time dependent manner. These results indicate that IL-4 inhibits the migratory activity of Langerhans cells by downregulating the expression of TNF-RII in human Langerhans cells and thereby modulates the immune response in the skin.
Eruptive pseudoangiomatosis is a skin eruption characterized by millet-sized erythema with an anemic halo appearing on exposed body areas. Insect bites, particularly mosquito bites, have been reported as one of the causes of eruptive pseudoangiomatosis. We experienced two cases of eruptive pseudoangiomatosis and the eruption was seen on the face and upper extremities of two women aged 48 and 77 years old. The two cases consented to be experimentally bitten by Culex pipiens mosquitoes and Aedes albopictus to determine if eruptive pseudoangiomatosis could be experimentally elicited by these mosquitoes. Our results showed that several minutes after a C. pipiens mosquito bite, an erythematous spot appeared on the bite site, followed by the formation of an anemic halo surrounding the erythema in 30 min; a successful reproduction of eruptive pseudoangiomatosis. The erythema lasted for more than a week and was not accompanied by any pruritus. With A. albopictus, we were able to reproduce a milder eruptive pseudoangiomatosis eruption: in case 1, a smaller erythematous spot with an ill-defined halo which disappeared within 1 week; and in case 2, an immediate response consisting of a wheal and erythema but not eruptive pseudoangiomatosis. We demonstrated that eruptive pseudoangiomatosis was the response manifested in individuals who normally did not demonstrate any immediate or delayed reaction to insect bites; and the typical eruptive pseudoangiomatosis eruption was elicited by C. pipiens mosquito bites. However, the mechanism resulting in the manifestation of eruptive pseudoangiomatosis is still unknown.
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