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Tissue-resident γδ T cells form the first line of defense at barrier surfaces where they survey host tissue for signs of stress or damage. Following recognition of injury, γδ T cells play a crucial role in the wound-healing response through the production of growth factors and cytokines that promote proliferation in surrounding epithelial cells. To initiate this response, γδ T cells require interactions with a variety of epithelial-expressed costimulatory molecules in addition to primary signaling through their TCR. In the epidermis these signals include the coxsackie and adenovirus receptor (CAR), histocompatibility antigen 60c (H60c), and plexin B2, which interact with γδ T cell-expressed junctional adhesion molecule-like protein (JAML), NKG2D, and CD100, respectively. Here we identify heat shock protein family A member 8 (Hspa8) and ICAM-1 as two additional keratinocyte-expressed costimulatory molecules for epidermal resident γδ T cells (termed DETC). These molecules were rapidly up-regulated in the epidermis following wounding in both mouse and human tissue. Both Hspa8 and ICAM-1 had a costimulatory effect on DETC, inducing proliferation, CD25 up-regulation, and IL-2 production. We also provide evidence that DETC can be activated through the potential ICAM-1 and Hspa8 receptors LFA-1 and CD316. Finally, knockdown of Hspa8 in keratinocytes reduced their ability to activate DETC in culture and ICAM-1−/− mice exhibited impaired rates of healing in skin-organ culture suggesting a role for these proteins in the DETC-mediated damage response. Together with previous work on CAR, H60c, and plexin B2, these results add to a picture of a complex keratinocyte wound signature that is required for efficient DETC activation.

Eugenia brasiliensis Lam., a plant from the south of Brazil, is used in the popular medicine for rheumatism treatment. This study reports that topical application of hydroalcoholic extract, fractions and isolated compounds from E. brasiliensis caused an inhibition of ear oedema in response to topical application of croton oil on the mouse ear. For oedema inhibition, the estimated ID50 values (dose reducing the inflammatory response by 50% relative to the control value) for hydroalcoholic extract and fractions (hexane, ethyl acetate and dichloromethane) were 0.17, 0.29, 0.13 and 0.14 mg/ear, respectively, with inhibition of 79 ± 7%, 87 ± 6%, 88 ± 5% and 96 ± 2%, respectively. Isolated phenolic compounds (quercetin, catechin and gallocatechin) were also effective in inhibiting the oedema (inhibition of 61 ± 5%, 66 ± 2% and 37 ± 9%, respectively). Moreover, both extract and isolated compounds caused inhibition of polymorphonuclear cells influx (inhibition of 85 ± 6%, 81 ± 5%, 73 ± 6% and 76 ± 6%, respectively). The histological analysis of the ear tissue clearly confirmed that the extract and compounds of E. brasiliensis inhibited the influx of polymorphonuclear cells to mouse ear skin after application of croton oil. Furthermore, hydroalcoholic extract was also effective in inhibiting the arachidonic acid-mediated mouse ear oedema (ID50 value was 1.94 mg/ear and inhibition of 60 ± 7%). Therefore, these results consistently support the notion that E. brasiliensis possesses topical anti-inflammatory activity.