Functions of Fc Receptors on Human Dendritic Langerhans Cells

Immature dendritic cells are antigen presenting cells highly specialized for capturing and processing foreign protein antigens. These cells express FcγRII and FceRI which, by their ability to internalize and use the endocytic pathway, increase their capacity to process antigens. Immature dendritic cells, such as epidermal Langerhans cells, also release soluble forms of FcγRII. These latter molecules are likely to compete with the membrane-associated FcγR to diminish or abrogate the capacity of dendritic cells to present immune complexes, as suggested by our in vitro experiments using both human and mouse epidermal Langerhans cells. However, when dendritic cells mature in vitro and become efficient stimulators of resting T cells, they rapidly down-regulate and sometimes completely abolish the expression of their membrane-associated FcγR and FceRI. Consequently, they lose or at least strongly diminish their capacity to capture immune complexes. At this stage, the release of soluble FcγR by dendritic cells i...