This study aims to provide detailed phenotypes of F344-Il2rg KO, Rag2 KO, and Il2rg/Rag2 KO rats, shedding light on their overall health status, physiological parameters, and histopathological features in lymphoid organs correlated with the severe lymphopenia caused by Il2rg and Rag2 KO. This evidence concerns the gene RAG2 and lymphopenia.