Role of B cells in presentation of autoantigens to CD4(+) T cells in patients with autoimmune thyroiditis.

The antigen-presenting activity of B cells and expression of molecules involved in antigen presentation by B cells have been studied in patients with autoimmune thyroiditis (AIT). The disease is characterized by enhanced expression of the costimulatory molecule CD80 in naive B cells (CD19(+)CD27(-) cells) both ex vivo and under the conditions of polyclonal cell activation in a culture. Under in vitro conditions, antigen-loaded B cells have been shown to be capable of inducing proliferation of autologous CD4(+) cells, in particular, proliferation of autospecific T cells in patients with AIT. Given that an intense infiltration of thyroid tissue by B cells is a typical sign of AIT, the antigen-presenting activity of B cells appears to contribute to this pathology.