The protective effect of sunscreens against ultraviolet B-induced immunosuppression. A study on Langerhans cell depletion

Abstract

Ultraviolet B (UVB) radiation can act as immunosuppressant by inducing an epidermal Langerhans cells (LC) depletion
which could be inhibited by topical sunscreen. Several kinds of sunscreens with various SPF (Sunscreen Protection
Factor) are now available. The minimal SPF which able to inhibit the immunosuppressive effect of UVB among
people with skin photo-type IV has not been established yet. The aim of this study is to determine the minimal SPF
capable to inhibit UVB-induced immunosuppression among people with skin photo-type IV. A simple experimental
(post test only experimental) study was conducted among 5 people’s circumsized foreskins with Fitzpatrick’s skin
photo-type IV. Each of them was divided into equal 5 pieces of 0.5 cm2. Each of three pieces of skin was treated by
sunscreen SPF 15, SPF 30, and SPF 50, a single piece of skin was treated with placebo, and all of them then were
treated by a single 100 mJ/cm2 of UVB 30 minutes later. A rest single piece of skin was used as control. After 24
hours of incubation in incubator of 37O C and 5% CO2, all of them then was fixed by buffer formalin, blocked by
paraffin, cut in 2mm of thickness, and then stained with anti CD 1a antibody with AEC as chromogen and Mayer’s
hematoxylin as counterstaining. The number of LC was counted by Image J Analysis programmed and the mean of
LCwere analyzed by Kruskal-Wallis test dan Mann-Whitney test. There were very significantly different of the
mean number of LC between UVB placebo group and control group (p < 0.01). Compared to the control group,
mean number of LC among SPF 30 and SPF 50 treated groups were not significantly different (p>0.05). Sunscreen
with SPF 15 had LC number lower than control group significantly (p<0.05). The lowest SPF for preventing UVB
induced LC depletion among people with skin photo-type IV was 30.
Key words : UVB - immunosupression – sunscreens – SPF -CD1aexpression