Consistently, transfer of CD4+ T cells deficient in signal transducer and activator of transcription 6 (STAT6), a transcription factor important for Th2 polarization, into obese Rag1-null mice resulted in the reduction in Th2 cells in VAT and the loss of protective effects on obesity-related metabolic parameters in recipient Rag1-null mice (86). This evidence concerns the gene RAG1 and obesity due to melanocortin 4 receptor deficiency.