Incorporation of monoclonal antibodies in living rat pheochromocytoma PC12 cells. Evidence for the intracellular formation of immune complex between the incorporated antibody and a target protein.

PC12 cells permeabilized with a low concentration of digitonin (5 microM) under controlled conditions were loaded with monoclonal antibodies (MoAb) against the regulatory subunit type II (RII) of cAMP-dependent protein kinase. After digitonin removal from the nutrient medium (DMEM) the loaded cells repaired within 20-30 min and recontinued growth. The inserted MoAb stayed in the repaired cells at least for several hours. MoAb inhibiting the cAMP binding activity of neural RII [Grozdova et al. (1992) Biochem. Int. 27, 811-822; Sveshnikova et al. (1996) Biochem. Int. 39, 1063-1070] were shown to bind the target antigen inside the cells and influence the properties of intracellular protein kinases.