CD28 and B-cell non-Hodgkin lymphoma: In the restimulation of in vitro primed 5C.C7 T cells with CH27 B cell lymphoma APCs and MCC peptide IL-2 amounts in the supernatant were reduced upon blockade of the CD28 ligands CD80 and CD86 (‘costimulation blockade’) and in T cells from Itk knock out 5C.C7 TCR transgenic mice, in particular at lower peptide concentrations (Figure 1A).