The leukocyte differentiation antigen, CD50, has been recently identified as the intercellular adhesion molecule 3 (ICAM-3), the third counter-receptor of leukocyte function-associated antigen 1 (LFA-1). This molecule seems to be specially involved in the adhesion events of the initial phases of the immune response. To characterize the role of CD50 in leukocyte interactions, the different molecular events induced after cross-linking of CD50 on T cell-derived Jurkat cell line have been analyzed. When cells were incubated with anti-CD50 mAbs and cross- linked with polyclonal goat anti-mouse immunoglobulins, a rise in intracellular calcium concentration ([Ca2+]i) was observed. This increase in [Ca2+]i was mainly due to the uptake of extracellular Ca2+. This Ca2+ flux involved tyrosine phosphorylations and was further increased by CD3 costimulation. These data, together with those obtained by phosphotyrosine (P-Tyr) immunoprecipitation and in vitro kinase assays, suggested the involvement of protein-tyrosine kinases (PTK) in CD50 transduction pathways. By using specific antisera, the presence of p56lck and p59fyn protein tyrosine kinases (PTK) was clearly demonstrated in the CD50 immunoprecipitates. These findings suggest that the interaction of CD50 with its natural ligand (LFA-1) may result in T lymphocyte activation events, in which CD50 could play a very active role after antigen triggering.

Ski industry has become one of the main economic activity for many mountain regions worldwide. However, the economic viability of this activity is highly dependent of the interannual variability of the snow and climatic conditions, and it is jeopardized by climate warming. In this study we reviewed the main scientific literature on the relationship between climate change and the ski feasibility under different climate change scenarios. In spite of the different methodologies and climate change scenarios used in the reviewed studies, their findings generally point to a significant impact of climate change on ski industry caused by a reduction in the natural availability of snow as well as a contraction in the duration of seasonal conditions suitable for ski. It emphasizes that the problem is real and should not be ignored in the study and management of tourism in mountain regions. However, there were significant differences in the impacts between different areas. This differences are mainly associated to the elevation of the ski resorts, their infrastructures for snowmaking and the various climate models, emission scenarios, time horizons and scales of analysis used. This review highlights the necessity from scientist to harmonize indicators and methodology thus allowing a better comparison of the results from different studies and increase the clarity of the conclusions transmitted to land managers and policy makers.Moreover, a better integration of the uncertainty in the model´s outputs, as well as the treatment applied to the snowpack in ski slopes is necessary to provide more accurate indications on how this sector will respond to climate change.

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