IL13 and chronic graft versus host disease: However the proportion of CD4+ T cells generating cytokines, such as TNF-α, TGF-β, IL-21 and IL-13, which are critically involved in chronic GVHD (23), was significantly reduced in mLN from CpG-proB recipients (Figure 4C), while only IL-13-expressing CD4+ T cells were diminished in pLN (Figure 4D).