The hemolytic activity of (Fab-Fc) recombinant immunoglobulins with specificity for the sheep red blood cells.

Antibody-like molecules were formed by artificial recombination of proteolytic IgG fragments (Fab' with anti-SRBC activity, and Fc) and used for studies concerning the complement fixation. Such molecules, when composed of single Fab' bound to Fc fragment appeared inactive, while species containing two Fab' fragments revealed the hemolytic activity. The results were discussed and interpreted, assuming that the interaction of Fab domains with CH2 domains in the Fc fragment is a main structural effect influencing the binding of the complement.