Radiolabeled antibodies, albumin and antimony sulfide colloid: a comparison as lymphoscintigraphic agents

The kinetics of lymph node and systemic uptake of members of three different classes of lympho-scintigraphic agents were studied in normal laboratory rats. sup(99m)Tc antimony trisulfide colloid (TcSbC), sup(99m)Tc human serum albumin (TcHSA), 125I 5G6.4 (a murine IgG2ak monoclonal antibody), 125I 763.24T (a murine IgG1), and 125I FT166 (a murine IgM monoclonal) all current or potential lymphoscintigraphic agents, were injected subcutaneously into the hind foot pads of healthy rats. Ipsilateral and contralateral popliteal lymph nodes were sampled up to 4 h post-injection. Subcutaneous injection resulted in far higher nodal uptake for all agents than i.v. delivery with ipsilateral popliteal node/blood ratios 1 h post-subcutaneous injection of: for TcSbC (1900) > 125I IgM (497) > TcHSA (72) > 125I Intact IgG2a or 125I IgG1 at approximately 10. Thus, while all agents achieve popliteal node/blood ratios far greater than unity, TcSbC has the greatest absolute and relative nodal accumulation, greater than the 125I IgM monoclonal antibody and TcHSA. Uptake of the intact 125I IgG antibodies is lowest. These data suggest that TcSbC in particular, as well as TcHSA and IgM may be most useful as non-specific nodel imaging agents, while the lower background activity of the IgGs may make targeting specific antigen in nodes more feasible. (author)