Effects of skin exposure to ultraviolet radiation on immune cell populations. Differences between high and low UV doses.

E. CELA; M. PAZ; F. WEILL; J. LEONI; D. GONZALEZ MAGLIO

Buenos Aires, Argentina

Congreso; First French-Argentine Immunology Congress; 2010

Sociedad Argentina de Inmunología

Skin exposure to UV radiation (UVr) is associated with a negative impact on humanhealth, due to the increment in skin tumor incidence, exacerbation of infectiousdiseases and photoaging. However, there is also evidence showing“immunostimulatory” effects of UVr exposure. The mechanisms involved includeproduction of antimicrobial peptides and activation of TLR‐2 pathway, through anincrease in Vit D.The aim of the present work is to evaluate the effects on the skin, inguinal and axylarlymph node (LN) cell populations of two UVr exposure models: a single exposure to ahigh dose (HD: 400mJ/cm2, proposed as harmful) and repetitive exposures to lowdoses (LD: 20 mJ/cm2, proposed as stimulatory).SKH:1 mice were separated into 5 groups of 5. Groups 1 and 2 received a HD and weresacrificed 1 and 8 days (d) post irradiation (PI), respectively. Groups 3 and 4 receivedLDs for 4 consecutive days and were sacrificed 1 and 8d PI, respectively. Group 5 wasthe unirradiated control group. Skin histological analysis (H&E), epidermal (Ep), LN Tcells and dendritic cells (DCs) populations (CD3, CD4, CD8, CD11c, CD80) wereevaluated.Both HD and LDs produced:No changes in Ep DCs number and activation profile at any time.An increment in CD3+CD4+ cells percentage in both LN, 1 and 8d PI (p<0.05).An increment in activated DCs in LN 1d PI (p<0.001), without changes in total DCsnumber.HD produced:A reduction in Ep thickness 1d PI (p<0.05) with a marked increment after 8d (p<0.001).A decrease in CD3+ Ep cell percentage 1d PI (p<0.05) leading to a depletion after 8d(p<0.01).LDs produced:An increment in Ep thickness 1d PI (p<0.001) and 8d PI (p<0.05).No changes in CD3+ Ep cells percentage at any time.Concluding remarksBoth UVr exposure models produced direct effects on the skin and on Ep and LNimmune cells, leading to an increase in DCs activity and helper T Cells number. We arecurrently studying in depth the Ag specific immunostimulatory effect of low doses ofUVr.