Mutations in the CD28 gene, which are present in 4%-12% of AITL cases, contribute to the hyperactivation and amplification of CD28 signaling via enhanced affinity for intracellular adaptor proteins (with the p.T195P/I mutation) or the CD28 ligands CD80 and CD86 (with the p.D124E/V mutation) (14, 17). Here, CD28 is linked to angioimmunoblastic T-cell lymphoma.