Extracts of scabies mites (Sarcoptidae: Sarcoptes scabiei) modulate cytokine expression by human peripheral blood mononuclear cells and dendritic cells.

We performed a series of experiments to determine if human peripheral blood mononuclear cells (PBMCs) from a healthy donor and dendritic cells (NHDCs) derived from these PBMCs reacted to molecules in a scabies extract. PBMCs extravasate from the circulatory system and enter tissues such as scabietic lesions, where monocytes become macrophages. Cells were cultured in medium alone or medium containing 50 microg/ml of Sarcoptes scabiei (SS) extract, 50 ng/ml E. coli lipopolysaccharide (LPS), or SS + LPS together. Supernatants were collected and assayed by enzyme-linked immunosorbent assay (ELISA) for specific cytokines. PBMCs stimulated with SS or LPS exhibited moderately upregulated production of interleukin (IL)-1beta and huge increases in secretions of IL-6, IL-8 and TNF-alpha. Cells co-stimulated with both SS and LPS generally secreted more of these cytokines than cells stimulated with either SS or LPS alone. LPS induced a small amount of IL-1alpha secretion, whereas SS did not, and neither additive resulted in the production of IL-10. NHDCs did not produce IL-1alpha, IL-1beta, IL-6, IL-8, or IL-10 in response to stimulation with SS. These cells did produce IL-6, IL-8, and tumor necrosis factor (TNF)-alpha in response to LPS. When cells were co-stimulated with both LPS and SS, the production of IL-6 and IL-8 was significantly reduced compared with the levels secreted after LPS stimulation alone. These studies show that molecules in a whole body extract of S. scabiei modulate the function of PBMCs (probably monocytes) and dendritic cells.

Modulation of cytokine expression in human keratinocytes and fibroblasts by extracts of scabies mites.

Sarcoptes scabiei lives in the stratum corneum of its mammalian host. Keratinocytes and fibroblasts are among the first cells to encounter the burrowing mite and its products. The aim of this study was to determine if molecules in an extract of S. scabiei modulate the expression of cytokines by keratinocytes and fibroblasts. Human keratinocytes and fibroblasts were exposed to an extract of S. scabiei var. canis in the absence or presence of Escherichia coli lipopolysaccharide. Cytokine expression was measured by an enzyme-linked immunosorbent assay. Components in the S. scabiei extract induced marked increases in secretion of interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) and slight increases in production of granulocyte-colony-stimulating factor (G-CSF) by keratinocytes. The scabies extract down-regulated keratinocyte secretion of IL-1 receptor antagonist, but did not influence the production of IL-1alpha or IL-1beta. In comparison, components in the scabies extract induced marked increases in the elaboration of IL-6, IL-8, G-CSF, and VEGF by fibroblasts. Neither cell type produced eotaxin, stem cell factor, or tumor necrosis factor-alpha under any of the conditions tested. This study demonstrates that components in an extract of the mite S. scabiei are able to influence cytokine expression by human keratinocytes and fibroblasts.

Dust mite allergens: ecology and distribution.

The most important allergy-causing mites found in homes worldwide are the house dust mites Dermatophagoides farinae, D. pteronyssinus, Euroglyphus maynei, and the storage mite Blomia tropicalis. Most homes contain multiple species. The most prevalent mite species and allergen in homes differ geographically, between homes within a geographical region, and among areas within a home. Therefore, it is important to know which mite species are present in a geographical area when performing diagnostic testing and prescribing immunotherapy. The key factor that influences mite survival and prevalence is relative humidity. Mites are present in homes in humid geographical areas and are rare or absent in drier climates unless humidity is artificially raised. Generally speaking, dust mite allergen levels are low in public buildings and transportation compared to levels in homes.

Relationship among house-dust mites, Der 1, Fel d 1, and Can f 1 on clothing and automobile seats with respect to densities in houses.

BACKGROUND: Locations where there are no dust mites or pets present may contain allergens that pose a risk factor for sensitizing and inducing rhinitis and asthma. OBJECTIVE: The purpose of this study was to investigate the relationship among the prevalence of mites and mite, dog, and cat allergens in homes, on clothing, and on automobile seats. METHODS: Over a 2-year period (July 1998 to July 2000), dust mite and mite, dog, and cat allergen densities were determined in homes, associated automobiles, and on the clothing of the drivers. During this period 87 homes were sampled one to five times each. RESULTS: Low levels of live and dead mites were present in most dust samples obtained from automobile seats and in 16% from clothing. Seventy-two and 50% of the home samples had >2 microg and >10 microg Der l/g of dust, respectively, whereas 23% of automobiles seat samples had >2 microg Der l/g of dust with a mean of 1.3 microg/g. Mite and Der 1 densities were not different for homes with or without pets. However, homes with pets had significantly more Fel d 1 or Can f 1 allergen than homes without pets. Homes without cats and dogs had an average of 93 and 29 microg/g of Fel d 1 and Can f 1, respectively, which was well above threshold levels for sensitization and induction of allergic reactions. Although most clothing had detectable levels of pet allergen, the levels of these allergens were low. CONCLUSIONS: Der 1 densities in some automobiles were sufficiently high (>2 microg/g of dust) to be risk factors for sensitization and allergic reactions. However, most automobile seats had levels of dog and cat allergen that were well above the threshold levels considered to be risk factors for both sensitization and symptoms, regardless of the presence of a pet in the home. The presence of live and dead mites and mite, cat, and dog allergens in automobiles and on clothing suggests that both are vehicles in the dispersal of mites and mite and pet allergen.