By using BM chimeras to observe antigen-specific Atg7−/− CD8+ T cell responses, we excluded a number of explanations as to why T-Atg7−/− mice fail to form CD8+ Tmem: (1) lymphopenia, (2) defective CD4+ T cell help, and (3) the excision of Atg7 in CD4-expressing antigen-presenting cells affecting CD8+ T cell priming. This evidence concerns the gene CD4 and lymphopenia.