The Reticuloendothelial System
The reticuloendothelial system (RES) is a heterogeneous population of phagocytic
cells in systemically fixed tissues that play an important role in the clearance of
particles and soluble substances in the circulation and tissues. Substances that are
cleared include immune complexes, bacteria, toxins, and exogenous antigens. These
molecules may be internalized by non-specific endocytosis, non-immune
receptor-mediated phagocytic action, or by immunocytophagic effects mediated by
binding to Fc or complement receptors. The composition of the reticuloendothelial
system includes Kupffer cells of the liver, microglia of the brain, alveolar
macrophages and bone marrow lymph nodes, and macrophages in the intestine and
other tissues. Reticuloendothelial block is a hypothetical mechanism for preventing
platelet damage by idiopathic thrombocytopenic immunoglobulin (1VGG). The
binding of Ig of G-Fc receptors on reticuloendothelial cells to Ig of G-sensitive
platelets, especially in the liver and sputum, can cause phagocytic action and platelet
destruction in ITP. The IgG-Fc receptor mechanism can be "blocked" or inhibited by
high doses of IVGG immersion, and the IgG-Fc receptor is lost during phagocytic cells
but can be expressed again after only a few days.
