Characterization of the TGF-α–positive granules in monocytes. Monocytes of the peripheral blood were double-labeled for TGF-α and for several components of the granules and vesicles, respectively. In (a) through (c), it is shown that TGF-α is localized in granules other than proteinase-3 (P-3), myeloperoxidase (MPO), and elastase (EL), markers of the peroxidase-positive granules of the monocyte. (d) No colocalization with albumin (AL), marker for a secretory compartment. (e) Colocalization with CD63, a membrane-bound glycoprotein. Bars = 200 nm