Moreover, the circulating level of the proinflammatory cytokines IL-6 (associated with the decline in the efficacy of thymopoiesis [49]) and TNF-α, which is shown to induce not only thymic atrophy [51], but also loss of CD28 expression on CD4+ T cells [23,24,52] was investigated. The gene discussed is CD28; the disease is thymus atrophy.