Dose response for UV-induced immune suppression in people of color: Differences based on erythemal reactivity rather than skin pigmentation

Ultraviolet radiation (UVR) is known to suppress immune responses in human subjects. The purpose of this study was to develop dose responses across a broad range of skin pigmentation in order to facilitate risk assessment. UV R was administered using FS 20 bulbs. Skin pigmentation and UVR sensitivity were evaluated using Fitzpatrick classifications, minimal erythemal dose ( MED). slope of the erythemal dose response curve (sED), baseline pigmentati on and tanning response, To assess immune responses dinitrochlorobenzene (D NCB) was applied to irradiated buttock skin 72 h after irradiation, Two wee ks later (DNCB) was applied to the inside upper arm, Skin thickness was mea sured before and after challenge, Dose response was modeled (to obtain a re gression line) for the entire group of 185 subjects. With the exception of sED none of the above-mentioned pigmentation indicators contributed signifi cantly to variability around the regression line. Thus, differences in sens itivity for multiple skin types based on Fitzpatrick classification or MED were not observed, However, differences in immune sensitivity to UVR were d etected between subjects with steep erythemal dose response curves and thos e with moderate or flat responses. For subjects with steep erythemal respon ses the dose calculated to suppress the immune response by 50% was 114 mJ/c m(2), This group included individuals with Fitzpatrick skin types I-V, MED for these subjects ranged from 30 to 80 mJ/cm(2), The 50% suppression dose for subjects with weak or no erythemal response could not be computed (the dose response was flat). This resistant group included subjects with skin t ypes IV-VI and MED for these subjects ranged from 41 to > 105 mJ/cm(2), Thi s study provides a human dose response for UVR suppression of contact sensi tivity that will he useful in risk assessment. It is the first study to pro vide this information using the FS sun lamp and is the first study to inclu de people of color. The sED appears to be a new variable for identifying se nsitive subjects at risk of UVR-induced immune suppression.