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

CELA ELIANA; PAZ, MARIELA; WEILL, FEDERICO; LEONI, JULIANA ; DANIEL GONZALEZ MAGLIO

Buenos Aires

Congreso; 1st. French-Argentine Congress. LVIII Reunión Anual de la SAI; 2010

Sociedad Argentina de Inmunología (SAI)

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 and D. González Maglio.  Skin exposure to UV radiation (UVr) is associated with a negative impact on human health, due to the increment in skin tumor incidence, exacerbation of infectious diseases and photoaging. However, there is also evidence showing “immunostimulatory” effects of UVr exposure. The mechanisms involved include production of antimicrobial peptides and activation of TLR-2 pathway, through an increase in Vit D. The aim of the present work is to evaluate the effects on the skin, inguinal and axylar lymph node (LN) cell populations of two UVr exposure models: a single exposure to a high dose (HD: 400mJ/cm2, proposed as harmful) and repetitive exposures to low doses (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 were sacrificed 1 and 8 days (d) post irradiation (PI), respectively. Groups 3 and 4 received LDs for 4 consecutive days and were sacrificed 1 and 8d PI, respectively. Group 5 was the unirradiated control group. Skin histological analysis (H&E), epidermal (Ep), LN T cells and dendritic cells (DCs) populations (CD3, CD4, CD8, CD11c, CD80) were evaluated. 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), with no changes in total DCs number. 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). LD 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 remarks Both UVr exposure models produced direct effects on the skin and on Ep and LN immune cells, leading to an increase in DCs activity and LTh number. We are currently studying in depth the Ag specific immunostimulatory effect of low doses of UVr.