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the fate of immune complexes is determined by certain properties:
| • | valence of the antigen (multivalent = multiple binding sites for antibody) |
| • | IgM and IgG (subclasses 1 to 3) activate classic complement pathway |
| • | IgA only activates the alternative complement pathway |
| • | molar ratio of antibody to antigen |
| • | large immune complexes are rapidly removed from the circulation by the reticuloendothelial system (especially the liver) |
| • | immune complexes formed at moderate antigen excess are maximally pathogenic (large enough to activate complement, but small enough to remain in circulation for long periods of time) |
| • | the RES can become saturated by large amounts of immune complexes, allowing prolonged circulation of larger immune complexes |
| • | ability of the antigen-antibody complex to activate complement |
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