The formation of soluble heat IgG aggregates for immunological studies.

The structural alteration associated with the aggregation of heated immunoglobulin molecules and the triggering of their effector reactivity was studied using soluble aggregate derivatives. Large but still soluble aggregate species were obtained by the formation of complexes of heated immunoglobulin molecules with azo dyes - Congo Red or Trypan Blue. Exposed peptide fragments in the area rearranged on heating were identified by short-lasting proteolysis. The altered area was in this way localized in the Fab portion of the heavy chain. The heavy chain fragment bordered by disulphides which stabilize the domains V and CH1 was indicated as a most probable peptide portion forming the link between the aggregating molecules. The obtained dye-aggregate species retain their effector activity. The effect of structural alterations in the Fab fragment on the Fc remains unclear.