Unconjugated Antibodies

8 Strategies for Specific Drug Targeting to Tumour Cells 

IgG2a is the one which is most efficient in mediating human ADCC, whereas IgG3 can mediate potent C-dependent cytolysis [39]. 

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This antibody is raised against the protein-based CD3 antigen, present on the cell surface of most T-lymphocytes. I.v. administration of (unconjugated) antibody appears to block normal functioning of such T-cells and promote their clearance from the blood. However, upon cessation of antibody administration, CD3 positive cell numbers rapidly revert to normal values. Therefore, maintenance immunosuppressives (e.g. with cyclosporine) must subsequently be restored. 

AP- and/or horseradish peroxidase (HRP)-conjugated antibodies for the haptens used for labeling probes (a direct detection method) or unconjugated antibodies for the haptens and AP- and/or HRP-labeled anti-species antibodies (an indirect detection method) (Vector Laboratories, Inc., Bnrlingame, CA, USA) (see Note 8). 

Pool fractions according to the determined content of conjugate and unconjugated antibody (see Note 21). 

The reaction must be driven to completion by a large excess of RNase, because it is very difficult to separate free unconjugated antibody from the RNase-antibody conjugate. The molecular weights of free antibody (160,000 kDa) and RNase-modified antibody differ only by 10-30 kDa (170,000-200,000 kDa) resulting in... 

F(ab) fragments of both conjugated and unconjugated antibodies are preferred in frozen section immunohistochemistry of lymphoid tissues in order to avoid nonspecific binding of antibodies through their FC fragments to Fc receptors (present on B lymphocytes) (17). 

Ward RL, Hawkins NJ, Smith GM. Unconjugated antibodies for cancer therapy lessons from the clinic. Cancer Treat Rev 1997 23 305-319. 

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