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BACKGROUND: The pathology of allergic diseases involves type 2 immune cells, such as Th2, ILC2, and basophils exerting their effect by production of IL-4, IL-5, and IL-13. However, surface receptors that are specifically expressed on type 2 immune cells are less well documented. The aim of this investigation was to identify surface markers associated with type 2 inflammation.METHODS: Naïve human CD4(+) T-cells were short-term activated in the presence or absence of IL-4, and analysed for expression of >300 cell-surface proteins. Ex vivo isolated PBMCs from peanut and non-allergic allergic subjects, were stimulated (14-16h) with peanut extract to detect peanut-specific CD4(+) CD154(+) T-cells. Biopsies were obtained for transcriptomic analysis from healthy controls and patients with extrinsic or intrinsic atopic dermatitis and psoriasis.RESULTS: Expression analysis of >300 surface proteins enabled identification of IL-4 up-regulated surface proteins, such as CD90, CD108, CD109, and CD200R (CD200R1). Additional analysis of in vitro differentiated Th0, Th1, and Th2 cultures, identified CD200R as up-regulated on Th2 cells. From ex vivo isolated PBMCs, we found high expression of CD200R on Th2 and ILC2 cells and basophils. In peanut-allergic subjects the peanut-specific Th2 (CD154(+) CRTh2(+) ) cells expressed more CD200R than the non-allergen specific Th2 (CD154(-) CRTh2(+) ) cells. Moreover, co-staining of CD161 and CD200R identified peanut-specific highly differentiated IL-4(+) IL-5(+) Th2 cells. Finally, transcriptomic analysis revealed up-regulation of CD200R in lesional skin from subjects with an extrinsic atopic dermatitis phenotype compared to healthy skin.CONCLUSION: These results indicate that CD200R expression strongly correlates with Th2 pathology; though, the mechanism is as yet elusive. This article is protected by copyright. All rights reserved.

In atopic dermatitis (AD), the inflammatory response between skin infiltrating T cells and keratinocytes is fundamental to the development of chronic lesional eczema. The aim of this study was to investigate whether skin-derived T cells from AD patients could induce an inflammatory response in mice through keratinocyte activation and consequently cause development of eczematous lesions. Punch biopsies of lesional skin from AD patients were used to establish skin-derived T cell cultures and which were transferred into NOD.Cg-Prkd(scid) Il2rg(tm1Sug) /JicTac (NOG) mice. We found that subcutaneous injection of the human AD skin-derived T cells resulted in migration of the human T cells from subcutis to the papillary dermis followed by development of erythema and edema in the mouse skin. Furthermore, the human T cells induced a transient proliferative response in the mouse keratinocytes shown as increased numbers of Ki-67(+) keratinocytes and increased epidermal thickness. Out of six established AD skin-derived T cell cultures, two were superior at inducing a skin reaction in the mice, and these cultures were found to contain >10% CCR10(+) T cells compared to <2% for the other cultures. In comparison, blood -derived in vitro differentiated Th2 cells only induced a weak response in a few of the mice. Thus, we conclude that human AD skin-derived T cells can induce a reaction in mouse skin through induction of a proliferative response in the mouse keratinocytes. This article is protected by copyright. All rights reserved.