Patients with HT display a peripheral T cell phenotype reminiscent of findings in elderly persons or other autoimmune disorders, such as rheumatoid arthritis[3,40] or JIA[4,31], with increased CD45RO + memory and CD28-negative T cells, increased peripheral replication and altered distribution of T cell proportions, such as CD62L-expressing T cells with accumulation of CD62L + lymphocytes in the thyroid gland. Here, CD28 is linked to hematocrit.