In the field of MDS and on bone marrow mononuclear cells , we search for a signature which predict the response to Lenalidomide treatment. This transcriptome study appended to the GFM-LEN-EPO-2008 clinical trial reports a predictive signature of response to lenalidomide and a unique immune response signature after treatment. Overall design: Examination of expression data before and after treatment by Len in non del(5q) MDS