GRO-alpha in normal and pathological thyroid tissues and its regulation inthyroid-derived cells

Thyroid glands affected by Graves' disease (GD) show striking leukocytic in filtration, mainly by T-cells. The mechanisms by which the various leukocyt es are maintained in the thyroid are unknown. Growth-regulated oncogene-alp ha (GFO-alpha) in interaction with its receptor CXCR2 is a chemoattractant for both T-cells and neutrophils and may be one of the chemokines involved in the cell maintenance. GRO-alpha and CD18 mRNA as a marker of leukocytic infiltration were quantif ied in thyroid tissue using competitive RT-PCR. We found very high GRO-alph a mRNA levels in all thyroid tissues. In GD patients (n=16), the GRO-alpha mRNA did not correlate with the CD18 mRNA level or thyroid peroxidase and T SH-receptor antibodies in patients' sera. In thyroid autonomy (n=10), the G RO-alpha mRNA levels were significantly lower in autonomous single adenomas compared with the corresponding normal tissue. In order to define the cellular source of GRO-alpha mRNA and protein, we ex amined various thyroid-derived cells. Thyrocytes, thyroid-derived leukocyte s and fibroblasts showed basal GRO-alpha mRNA and protein expression, which was remarkably upregulated by different stimuli in vitro. The expression o f GRO-alpha by thyroid carcinoma cell lines confirms that thyrocytes may ac tually produce GRO-alpha. As shown by flow cytometry and immunohistology, C D68(+) monocytes/macrophages are the only cell population strongly expressi ng CXCR2 in the thyroid.