An abnormal adherence of monocytes to fibronectin in thyroid autoimmunity has consequences for cell polarization and the development of veiled cells.

Blood monocytes of patients with thyroid autoimmune disease (TAID) display defects in rearranging their cortical actomyosin cytoskeleton ('polarize') in response to chemoattractants. Such rearrangements also take place after the adherence of monocytes to the extracellular matrix (ECM). It is therefore not surprising that monocytes are primed after fibronectin (FN) adherence, displaying an enhanced polarization toward chemoattractants. We investigated the integrin expression and chemoattractant-induced polarization of monocytes of TAID patients before and after FN adherence. Since cytoskeletal rearrangements are also required during the transition of monocytes into veiled antigen-presenting cells (VCs), we investigated such transition of FN-adherent monocytes of TAID patients. Adherent and nonadherent monocyte populations from TAID patients and healthy controls were subjected to a polarization test with the chemoattractant fMLP (or MCP-1), FACS analyses (FITC-labelled FN, CD29, CD49e, d, b and a) and tested for their capability to develop into veiled APC. Monocytes of healthy individuals showed an improved chemoattractant-induced cell polarization after FN adherence, not reflected by TAID monocytes, in which chemoattractant-induced polarization worsened. Monocytes of healthy individuals up-regulated CD49e and d integrins and their capability to bind FITC-labelled FN after adherence to a FN-coated plate, as well as enhancing their capability to generate T cell-stimulatory VCs. Monocytes of TAID patients did not. These data indicate that integrin- (and chemokine-) mediated functions are hampered in monocytes of TAID patients. Because integrin action is pivotal to processes such as monocyte adherence to endothelial cells, uropod formation, migration into tissues and differentiation into APC and macrophages, these defects might underly immune dysbalances important in thyroid autoimmune development.