In the present paper the distribution of peripheral blood CD5+/CD19+ (
CD5+B) and CD5-/CD19+ (CD5-B) B-lymphocytes in Graves' disease (GD) pa
tients is analyzed in order to correlate them with disease activity, i
nterleukin-2 (IL-2) and IL-6 binding to T and B cells as well as with
anti-thyrotropin (TSH) receptor antibodies and the thyroid hormone ser
um levels. The combination of flow cytometry and 3-color immunofluores
cence revealed a remarkable increase in the absolute numbers of CD5+ B
cells in hyperthyroid-untreated GD patients (218 +/- 137 x 10(6)/l vs
. 66 +/- 69 x 10(6)/l in healthy subjects, p < 0.01) that gradually fe
ll to normal values once hyperthyroidism had been controlled by methim
azole. However, relative numbers of CD5+ B cells persisted at a relati
vely stable but increased level in GD patients in long term remission
of an average of 3.1 years. This was also confirmed in a follow-up stu
dy of a group of 12 newly diagnosed patients during the first 90 days
of anti-thyroid drug therapy with methimazole. No correlation was obse
rved between either CD5+ B cells or CD5- B cells acid the serum levels
of pathogenic anti-TSH receptor antibodies. Increased numbers of CD5 B cells were related to the increased free thyroxine and total triiod
othyronine serum levels. In addition, a strong correlation between bot
h the absolute levels of B cells binding to exogenous IL-2 and IL-6 an
d the absolute number of CD5+ B cells in hyperthyroid GD patients (LR
= 0.798, p < 0.001; LR = 0.569, p < 0.01, respectively) was observed.
These results suggest that CD5+ B cells in GD are partly regulated by
thyroid hormone serum levels as well as by IL-2 and IL-6 binding to B
cells. Nevertheless, they are not involved, at least directly, in the
production of anti-TSH receptor antibodies.