Function of Fey receptors

Several approaches can be taken to determine the function of the different neutrophil Fey receptors during binding to immune complexes  

In view of the fact that neutrophils isolated from some inflammatory sites have been exposed to agents that selectively activate their gene expression (which may result in the expression of FcyRI see Fig. 7.9 and 8.9), such molecular adaptation of neutrophils to their environment may indeed occur. 

FcyRIII is actively synthesised by blood neutrophils, and its rate of expression can be increased up to twofold after exposure of neutrophils to GM-CSF ( 7.3.3). It is also shed from the membrane during activation by, 

In resting neutrophils, about 50% of the total cellular FcyRIII pool is expressed on the cell surface. There is considerable variation in this value because many methods used to isolate neutrophils can also inadvertently mobilise these subcellular receptors. The remainder of the total cellular FcyRIII that is not expressed on the plasma membrane is present in the subcellular pool. However, if the FcyRIII normally present on the plasma membrane is cleaved (e.g. via the action of elastase or pronase) and the cells subsequently activated, then FcyRIII reappears on the cell surface via the mobilisation of these pools. Thus, the expression can be restored to up to 70% of the resting level within 15 min via such a translocation. During activation (and presumably priming), FcyRIII (together with other plasma membrane markers) is also translocated to the plasma membrane however, because the receptor is also shed from the cell, the total number of receptors on the cell surface remains largely unchanged. There is also some evidence that continued expression of FcyRIII on the cell surface requires de novo biosynthesis of this receptor (see Fig. 7.8). 

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