Immunohistochemical localization of somatostatin receptor sst2A in sarcoid granulomas

In a previous study, we demonstrated the presence of receptors for somatostatin, a neuropeptide with immunoregulatory properties, in the inflammatory lesions of patients suffering from sarcoidosis and other granulomatous diseases by in vivo somatostatin receptor scintigraphy and in vitro autoradiography. However, it was not possible to identify exactly which cell types expressed the somatostatin receptors and which subtype was expressed. In this study we used a polyclonal antiserum directed against the sst2A receptor to identify more accurately the sst2A-expressing cells in sarcoidosis and other granulomatous diseases.

Tissue biopsies from 12 patients with sarcoidosis, one patient with giant cell arteritis and one patient with Wegener's granulomatosis were studied by immunohistochemistry with the sst2A-specific antiserum. Two of the sarcoidosis patients were treated with the somatostatin analogue octreotide (100 microg t.i.d.).

Epithelioid cells, multinucleated giant cells and a subset of CD68+ macrophages stained positive for sst2A in 9 out of 12 of the sarcoid biopsies and in both non-sarcoid granuloma biopsies. Treatment with octreotide resulted in clinical improvement in one out of two treated patients.

The identification of somatostatin receptors on granuloma macrophages, epithelioid cells and giant cells, and the successful treatment of one patient with sarcoidosis with a somatostatin analogue, may offer new possibilities for treatment of granulomatous diseases.