A general theory for the precipitin reaction--based on Fc-mediated precipitation.

Fc-mediated immune precipitation is studied theoretically by computer simulation of precipitin curves and of zonal profiles of soluble immune complexes. Comparison with experiments indicates that Fc-mediated immune precipitation is caused by Fc-Fc interactions with association constants ranging from 10(5) to 10(7) liters/mole. The Langmuir adsorption isotherm is used for evaluation of these interactions. A general theory for the precipitin reaction is formulated, assuming it to be a three-stage process: 1st stage Formation of immune complexes, 2nd stage Precipitation due to coalescence of antibody-rich immune complexes, and 3rd stage Fc-mediated immune precipitation.