Some exogenous antigens, such as heat shock proteins or apoptotic bodies, gain access to the MHC class I processing pathway and initiate CTL responses, a process called cross-priming. To be efficient in vivo, this process requires endocytosis of the antigen by dendritic cells via receptors which remain unidentified. Here, we report that scavenger receptors are the main HSP binding structures on human dendritic cells and identify LOX-1 as one of these molecules. A neutralizing anti-LOX-1 mAb inhibits Hsp70 binding to dendritic cells and Hsp70-induced antigen cross-presentation. In vivo, to target LOX-1 with a tumor antigen using an anti-LOX-1 mAb induces antitumor immunity. Thus, the scavenger receptor LOX-1 is certainly a promising target for cancer immunotherapy.

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Phorbol myristate acetate (PMA)-induced superoxide radical (O(2)(-))-production in guinea pig peritoneal polymorphonuclear leukocytes (PMNs) was significantly lower than that in peripheral cells. To determine the role of phosphotyrosine proteins in the lower O(2)(-) production, the effect of ST638 and genistein, tyrosine kinase inhibitors, on PMA-induced O(2)(-) production in peritoneal PMNs was examined. PMA-induced O(2)(-)-production of the cells was increased by the pretreatment with ST638 or genistein, the increment depending on the inhibitor concentration. The p47phox level in the plasma membrane of PMA-stimulated PMNs was increased by the pretreatment with ST638, although the phosphorylated p47phox level in the cells was not altered by ST638. On the other hand, PMA-induced O(2)(-)-production of peripheral PMNs was not affected by the pretreatment with ST638, but that of cytochalasin B (CB)-primed peripheral PMNs significantly increased by further treatment with ST638. The phosphotyrosine protein level of peritoneal PMNs was higher than that of the peripheral cells, especially in cytosolic proteins including 50-60 and 70-85 kDa proteins, and that of the CB-primed peripheral cells was also higher than that of the intact cells in similar cytosolic proteins to those above. Further treatment of CB-primed peripheral cells with ST638 resulted in a lower level of phosphotyrosine proteins. These findings suggest that phosphorylation of some protein(s) at specific tyrosine residues inhibits the translocation of p47phox to the plasma membrane from the cytosol, resulting in lower O(2)(-)-generation in casein-induced peritoneal exudate PMNs.