 These proteins up-regulate production of CD40L (used in B-cell activation), IL-21 and IL-21R (used for division/proliferation), and IL-2, among other cytokines.T-regulatory cells produce CTLA-4, which can dampen an immune response and lead to increased anergy.CTLA-4 binds to CD86 with greater affinity than CD28, which impairs the co-stimulation necessary for proper T-cell activation.