Autoimmune thyroid diseases are the result of the breakdown of self-tolerance caused mainly by genetic and environmental factors. Retrovirus HTLV-1 has been implied as an important environmental factor causing these diseases. In order to obtain evidences of the participation of this retrovirus, 47 paraffin embedded thyroid tissues from 45 patients with Graves' disease and two with Hashimoto's thyroiditis were studied, together with six normal thyroid tissues obtained from autopsies and lymph node tissue from a patient infected with the HTLV-1, used as negative and positive controls, respectively. All tissues were submitted to immunohistochemistry for the detection of protein p19 (gag) and gp21 (env) of the HTLV-1, using a new antigen retrieval method and anti-p19 and anti-gp21 monoclonal antibodies. The median positivity percentage for proteins p19 and gp21 were, respectively: 30% and 41% (for females), 27% and 52% (for males) and 30% and 41% (for all). Five out of 6 normal thyroid tissues were positive for both proteins, with a median positivity percentage of 17% for p19 and 39% for gp21. Detection of proteins p19 and gp21 in thyroid tissues from patients with autoimmune thyroid diseases and in normal thyroid tissues might indicate the expression of genetic sequences of HTLV-1 integrated into the genome of these individuais or may represent molecular mimicry and cross-reaction caused by the presence of shared antigens between HTLV-1 proteins p19 and gp21 and thyroid follicular epithelial cells.
Graves' disease; Hashimoto's thyroiditis; HTLV-1; Autoimmune thyroid disease; Endogenous retroviruse
