Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Circulating Intermediate Monocytes Produce TARC in Sarcoidosis

Abstract

Sarcoidosis is a systemic granulomatous disorder, but its mechanism is largely unknown. Chemotactic molecules may contribute to granuloma formation by immobilizing leukocytes at affected sites.1 We have recently found that thymus- and activationregulated chemokine (TARC), also known as CCL17, was elevated in the sera of patients with sarcoidosis, and TARC was abundantly expressed in the epithelioid cells of cutaneous granulomas.2 Peripheral monocytes have been classified into 3 subsets according to the expression of CD14 and CD16. Based on this nomenclature, approximately 90% of human peripheral monocytes express high levels of CD14, but not CD16, and have been categorized as classical monocytes (CD14þþCD16-). Two minor populations include intermediate monocytes (CD14þþCD16þ) and nonclassical monocytes (CD14þ CD16þþ).3 Among them, intermediate monocytes reportedly expand in a number of inflammatory conditions, including sarcoidosis.4e7 Because monocytes were reported to be a source of TARC in peripheral blood,8 we sought to evaluate the role of intermediate monocytes