Recognition and response in mononuclear and granular phagocytes
Wilkinson, P.C.
Clinical and Experimental Immunology 25(3): 355-366
1976
ISSN/ISBN: 0009-9104 PMID: 786516 Document Number: 99185
Mononuclear phagocytes and neutrophils migrate towards or ingest a wide variety of extracellular materials but do not respond to intact, native, homologous cells or molecules. This discrimination suggests that they can recognize differences between different materials in their environment and that recognition is followed by an appropriate response. Recognition by phagocytes may be non-specific and due to physicochemical affinities between the cell and the recognized material which do not require spatial complementarity or fit between the 2 reactants. This would provide an economical explanation for recognition of the wide range of materials which excite responses in phagocytes. Hydrophobic interactions would probably play a major role in such non-specific binding. The attachment sites on phagocytes for Fc and for complement enormously extend the capacity of these cells for recognition, since they allow them to use immune recognition, and thus to distinguish self from non-self. Attachment of Ig and complement molecules to the phagocytic cell is probably non-specific. Activation of cell function by cell-bound antibody probably follows clustering by polyvalent antigen and may require a conformational change in the membrane-bound Fc portion of the antibody molecule. Clear evidence that phagocytic functions can be activated upon binding of extrinsic molecules to stereospecific integral cell-membrane receptors is still awaited. Transduction probably involves an increase in membrane permeability, possible to ions, but it is not clear how this operates. Cytoplasmic actin-myosin microfilaments and microtubules probably play a role in mediating the cytoplasmic movements necessary for chemotaxis and phagocytosis; microfilaments provide the motor mechanism while microtubules act as a cytoskeletal scaffolding.