CD4 and lymphoma: The MD-susceptible line P and 7 had significantly higher percentages of TGF-beta+CD4+ T cells (Fig 4B) and TGF-beta+CD4+CD25+ T cells (Fig 4C) than the MD-resistant line N, demonstrating that there is an association between high frequencies of TGF-beta+ Treg cells in the spleens and susceptibility to MDV-induced lymphoma formation (p = 0.0008).