CD5 B cells in autoimmune and non immune-mediated thyroid dysfunction

In a previous study we demonstrated a significant increase of CD5+ B subset in patients with Graves' disease (GD) compared with normal controls. The aim of this study was to compare the percentage of CD5+ B and CD5- B cells in GD with that in different forms of autoimmune and non immune-mediated thyroid diseases. Seventy-two patients were studied: 28 patients with GD, 20 with silent thyroiditis (ST), 12 with Hashimoto's disease (HD), and 12 subjects affected by hyperthyroidism due to toxic adenoma (TA). Eleven out of 28 patients with GD were also evaluated after six months of methimazole treatment. The study was performed by cytometric analysis. In GD the percentage and the absolute number of CD5+ B cells were significantly increased compared with normal controls (42.5 +/- 18.2% versus 19 +/- 6.3%, p < 0.0001; 142 +/- 153.3/cmm versus 46.9 +/- 22/cmm, p < 0.003, respectively. CD5+ B cells tended to normalise after six months of treatment. In ST the percentage of CD5+ B cells was increased (28.6 +/- 10.2%); conversely the absolute number was in the normal range. Patients affected by HD did not show any significant modification in B cells and their subsets in comparison with controls. In TA, CD5+ B were 7.6 /- 4.4% and 14.3 /- 10.9/cmm. Our results demonstrated a marked increase in both percentage and absolute number of CD5+ cells, only in active GD. The expansion of CD5+ B cells could play a role in the immune imbalance present in this disease.