Adhesion molecules and lymphocyte recruitment in lymphocytic thyroiditis, thyroid papillary carcinoma and parotid adenolymphoma.

Lymphocytic infiltrates are usually present in chronic lymphocytic thyroiditis, thyroid papillary carcinoma and parotid adenolymphoma. We selected these conditions to investigate the mechanisms of recruitment and organization of lymphocytic infiltrates in extranodal tissues. MoAbs in immunoperoxidase were used to identify the expression of ICAM-1 and VCAM-1 on endothelial cells (EC), and of their ligands LFA-1 and VLA-4 on lymphocytes and accessory cells. VCAM-1 positive EC were rarely observed in thyroids devoid of lymphocyte infiltration. Conversely, EC in chronic lymphocytic thyroiditis and in papillary carcinoma showed positive immunostaining for VCAM-1 and ICAM-1. These findings were associated with the presence of lymphocytes positive for the ligands VLA-4 and LFA-1. The upregulated expression of VCAM-1 on perifollicular capillaries was co-distributed with an accumulation of VLA-4 positive lymphocytes. In adenolymphoma, all EC were ICAM-1 positive, whereas the majority of vessels were VCAM-1 negative. Consequently the majority of lymphoid cells were LFA-1 positive and VLA-4 negative. We suggest that ICAM-1 and VCAM-1 expression on EC play a role in the recruitment of lymphocyte infiltration in chronic lymphocytic thyroiditis and papillary carcinoma. Furthermore, the upregulation of VCAM-1 and VLA-4 in thyroid reactive and neoplastic conditions may be linked to an immune response possibly related to thyroid tissue antigens.