Suppression of contact hypersensitivity after repeated exposures of humans to low doses of solar simulated radiation

Abstract

Although it is generally recognised that UV radiation (UVR) can induce suppression of contact hypersensitivity (CHS) in human subjects, most protocols to date have not tested the effect of low daily doses of solar simulated radiation (SSR). In the present study, healthy individuals, divided into four groups each consisting of approximately 34 subjects, were whole-body irradiated with 1.2 standard erythema doses of SSR for 2, 10 or 30 consecutive days, or were unirradiated. They were sensitised with diphenylocyclopropenone (DPCP) on one exposed body site 24 h after the final UVR. The occurrence and severity of the primary allergic response were noted, and both parameters were shown to be significantly lowered in the group irradiated for 30 days compared with the unirradiated group. Elicitation of CHS was undertaken 3 weeks after the sensitisation, using a range of concentrations of DPCP on a UV-protected body site. The extent of the CHS at 48 h was assessed by the clinical score, by an erythema meter and by histological examination of a biopsy taken from the site challenged with one selected concentration of DPCP. Although erythema and pigmentation did not differ between the groups, a significant negative correlation was found between the clinical CHS score and the number of days of UV exposure, at the lowest challenge dose of DPCP. In addition a significant negative correlation was revealed between the intensity of spongiosis (intraepidermal oedema and vesicles, as evaluated by histology) and the number of days of UV exposure. Thus small daily doses of SSR induce suppression of CHS in human subjects and the effect is cumulative, indicating that there is no adaptation to the immunomodulating effects of UVR, at least over the test period of 30 days.

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“…These authors also studied the effect of 10 full-body tanning exposures in 11 volunteers and, not surprisingly, reported the presence of CPD and p53 protein expression in keratinocytes in vivo (Whitmore et al, 2001). One study used a Cleo Natural source (see Figure 1) to assess the immunological effects of repeated whole-body sub-erythemal exposure (1.2 SED) on 165 skin types II and III for up to 30 consecutive days (Narbutt et al, 2005). The results showed a cumulative UVR dose-dependent reduction of the primary allergic response and the elicitation arm of the CHS response and suggest that there is no adaptation to these immunological responses.…”

Repeated exposures of humans to low doses of solar simulated radiation lead to limited photoadaptation and photoprotection against UVB-induced erythema and cytokine mRNA up-regulation

“…In real life, many human subjects go outside for short periods of time on a daily basis during the summer months and respond by tanning and epidermal thickening. To mimic this type of exposure, we assessed the contact hypersensitivity response in individuals irradiated daily for up to 30 days with a low dose of solar simulated radiation (SSR) [4]. Now we extend these observations by assessing whether photoadaptation to the induction of four cutaneous cytokine mRNAs occurred as a result of repeated SSR exposures.…”

“…Four groups were established ( Table 1): group A subjects were non-irradiated controls; group B subjects were whole-body irradiated (excluding the external genitalia) with 1.2 standard erythema dose (SED where one SED is equivalent to an erythemal radial exposure of 100 J/m 2 ) SSR on each of 10 consecutive days followed 24 h later by one dose of three MEDs UVB on the left buttock, 10 cm  10 cm; group C subjects were irradiated with one dose of three MEDs UVB on the left buttock, 10  10 cm; and group D subjects were whole-body irradiated with 1.2 SED SSR on each of 30 consecutive days. The SSR was generated by Cleo Natural lamps as described previously [4]. Erythema was quantified on the left buttock using the UV Optimise 555 device [6] before and 24 h after irradiation.…”

Stratospheric ozone, global warming, and the principle of unintended consequences—An ongoing science and policy success story

“…The most conspicuous health effects are melanoma, basal-cell carcinoma and squamouscell carcinoma (Chang et al, 2009;de Gruiji et al, 2003;Kripke, 1974;Norval et al, 2007;Swaminathan and Lucas, 2012;van Hattem et al, 2009;van der Leun and de Gruijl, 2002;van der Leun et al, 2008), and cataracts (Ayala et al, 2007;Meyer et al 2008;Oriowo et al, 2001;Norval et al, 2007;Vojnikovic et al 2007;Rivas et al, 2009). The most uncertain health effects are the suppression of the human immune system (Damian et al, 1998;Narbutt et al, 2005;Norval et al, 2007;Wang et al, 2008). The most economically damaging impact might have been to agricultural and natural ecosystems (Caldwell, 1971;Caldwell et al, 1986;Caldwell et al, 2007).…”