The use of flow calorimetry in antigen-antibody reactions

The binding of anti-IgM IgG to human monoclonal IgM has been studied calorimetrically and results have been compared with parallel turbidity measurements of the same reaction. In the first series of experiments using the flow calorimeter equipped with a mixing cell, varied flow rates gave identical values for the thermic contribution, indicating that the same quantity of heat was evolved in the different time intervals in which the reaction mixture was in the calorimetric cell. In the second set of experiments a flow-through cell was used. Reactants were mixed outside the calorimeter and no heat was detected upon entry of the pre-mixed reactants into the calorimetric cell. Results suggest that heat is evolved instantaneously upon mixing and no heat is produced during aggregation. Antibody-antigen binding can be followed in the absence of precipitation, as may occur in reactions involving monoclonal antibodies.