**5.1 Tc-99m labelled Anti-granulocyte antibody: Pharmacological and physiochemical characteristics**

Three anti-granulocyte antibodies have been used including anti-NCA-95 immunoglobulin IgG, fanelosomab (a monoclonal murine M class immunoglobulin), sulesomab (a murine monoclonal antibody fragment anti-NCA-90 Fab) and anti-CD15. Presently most routinely sulesomab (Leukoscan ®) is used in clinical practice.

Leukoscan consists of a small murine monoclonal antibody fragment, sulesomab, labelled with Tc-99m. The radiolabelled antibody fragment (Fab) reacts with the normal cross reacting antigen (NCA-90) present on the surface of virtually all neutrophils. Therefore areas where neutrophils have accumulated can be detected and this proves useful in determining the location and extent of infection and inflammation. Uptake at sites of infection is therefore related to migration of antibody labelled circulating granulocytes and non-specific non-antigen related uptake of free antibody. The use of radiolabelled monoclonal antibodies against surface antigens as present on granulocytes has the advantage that labelling procedures are easier and do not require handling of potentially contaminated blood. Since the leukocytes are not removed from the patient, it is considered as in-vivo labelling process. Mounting of an immune response and production of human anti-mouse antibodies (HAMA) may pose a concern; however, in our experience and available published data the level of adverse events and probability of HAMA response are both low.
