Differences in Thyroid-Infiltrating B Lymphocytes in Patients with Graves' Disease: Relationship to Autoantibody Detection

Objective: Thyroid-infiltrating B (Thyr-B) lymphocytes are thought to play an important role in the pathogenic mechanisms underlying Graves' disease. Design and methods: In this study, a broad phenotypic analysis of these cells has been performed in 15 consecutive patients who underwent thyroidectomy. Results: Data reveal the occurrence of two distinct types of Thyr-B cell infiltrates. Type 1 was present in most of the cases (10/15) and consisted of a combination of IgM+ IgDlow to- B lymphocytes showing features of marginal zone B cells, and IgG+ classic memory B cells. In contrast, in 5 of the 15 cases, a second type of Thyr-B cell infiltrate occurred, exhibiting the profile IgM- IgD- CD44low to- CD38++ CD71+ CD95+. This phenotype is highly suggestive of germinal center (GC) B cells, a finding not always anticipated from routine histologic examination. The presence of these ectopic GC was closely associated with the elevated serum level of anti-thyroid peroxidase (TPO), but not with anti-thyrotropin rece...