This work was supported by the Portuguese Foundation for Science and Technology (FCT), project grant to SS – PTDC/SAU-GMG/64043/2006. PIM (SFRH/BD/68940/2010), ZF (SFRH/BD/45907/2008), JF (SFRH/BD/43763/2008), PC (SFRH/BPD/26553/2006), and JSC (SFRH/BPD/48765/2008) are supported by FCT fellowships and funded by POPH-QREN – Promotion of scientific employment, supported by the European Social Fund and national funds of the Ministry of Education and Science. SS and RMH are supported by the programme ‘‘Cieˆncia 2007’’, financed by the POPH-QREN – Promotion of scientific employment, cofinanced by the European Social Fund and national funds of the Ministry of Education and Science. Institute of Molecular Pathology and Immunology of the University of Porto is an Associate Laboratory of the Portuguese Ministry of Education and Science and is partially supported by FCT.