We have previously reported that antigens coupled to the surface of liposomes comprised of unsaturated fatty acid are presented to both CD4 + -and CD8 + T cells [23] . Confocal laser scanning microscopic analysis demonstrated that a portion of the liposome-coupled antigens were taken up and processed beyond the MHC class II compartment. In the present study, we confirmed that OVA coupled to oleoyl liposomes was processed at both the MHC class I and class II compartments ( Fig. 1 ). Flow cytometric analysis demonstrated that OVA coupled to oleoyl liposomes was incorporated more efficiently by macrophages than OVA coupled to stearoyl liposomes (Fig. 2) . Furthermore, OVA coupled to oleoyl liposomes was taken up by macrophages even in a 4uC environment, in which antigen entry could only occur via plasma membrane translocation. In general, antigen processing pathways largely depend on the route of antigen uptake, and liposomes with a certain lipid component are known to fuse with the plasma membrane [27] . The uptake of OVA coupled to oleoyl liposomes in a 4uC environment observed in the present study suggested that oleoyl liposome might fuse with the plasma membrane and thereby allow the liposome-coupled antigen direct access to the cytosol. The role of endocytosis in the uptake of the liposomal antigen was further examined by using specific inhibitors for antigen uptake (Fig. 3) . Cytochalasin B treatment of APCs prior to the addition of liposomal antigen in the culture had little effect. However, treatment of APCs with DMA significantly reduced the uptake of liposome-coupled OVA. Consequently, it was suggested that antigens coupled to oleoyl liposomes might be taken up by APCs via at least two pathways, penetration and pinocytosis. The analysis of intracellular pathways of antigens coupled to oleoyl liposomes using confocal laser scanning microscopy demonstrated that a portion of liposomal antigens taken up by APC were translocated to the lysosomal compartments expressing LAMP-1 (Fig. 4) , suggesting that the liposomal antigens processed at lysosomal compartment and beyond lysosomal compartment might be presented to CD4/ CD8 + T cells via MHC class II and class I, respectively. In agreement with the results of antigen uptake shown in Fig. 3 , the treatment of splenic CD11c + cells with DMA significantly reduced antigen presentation of liposomal antigens to both CD4 + -and CD8 + T cells as evaluated by T-cell activation (Fig. 5) .