IL4 and viral infectious disease: In the spleen, where a blunting of the CD8 T cell response is observed, the iNKT cells express a phenotype with pronounced expression of il4 and il13. In the CNS the infiltrating iNKT cells express higher levels of pro-inflammatory or even cytotoxic genes, implying a pro-inflammatory phenotype of iNKT cells locally at the site of viral infection.