Fc receptors for IgG and antigen presentation on MHC class I and class II molecules.

Antigens internalized through specific membrane receptors are presented to helper CD4(+) T cells at antigen concentrations 10(3) to 10(4) fold lower than antigens internalized by fluid phase. B lymphocyte antigen receptors, mannose receptors and receptors for the Fc region of immunoglobulins, promote both internalization and efficient presentation at low antigen concentrations. Thus, binding to specific membrane receptors concentrate antigens on antigen presenting cells and mediates efficient uptake. Is this 'quantitative' concentration of antigens on antigen presenting cells the end of the story? Or may 'quality', i.e. selective intracellular antigen targeting, somehow influence the efficiency or specificity of MHC class I and class II-restricted antigen presentation?