A new antigranulocyte antibody was evaluated in vitro for the detection of inflammatory foci in man. The specificity for polymorphonuclear cells (PMN) of NCA 102, an anti-NCA 95 monoclonal IgG1, was determined with immunohistochemical and cytofluorometrical tests. Its affinity, assessed by Scatchard analysis, was 1.1 x 10(9) L/mol and the number of epitopes per granulocyte reached about 10(5). The biological properties of PMNs incubated with NCA 102 were not inhibited even when coupled with DTPA. A F(ab)'2 fragment was radiolabelled with 111Indium and incubated in the presence of whole blood. More than 65% radioactivity was selectively taken up by the PMN population. These findings indicated that NCA 102 antibody is suitable for sepsis detection.

Direct labeling involves Tc-99m binding to different donor groups on the protein, giving multiple binding sites of various affinities resulting in an in vivo instability. The stability has been considerably improved by activating the antibody using a controlled reduction reaction (using 2-aminoethanethiol). This reaction generates sulfhydryl groups, which are known to strongly bind Tc-99m. The direct Tc-99m antibody labeling method was explored using whole antibodies and fragments. Analytical methods were developed for routine evaluation of radiolabeling yield and in vitro stability.Stable direct antibody labeling with Tc-99m requires the generation of sulfhydryl groups, which show high affinity binding sites for Tc-99m. Such groups are obtained with 2-aminoethanethiol (AET), which induces the reduction of the intrachain or interchain disulfide bond, with no structural deterioration or any loss of immunobiological activity of the antibody. The development of fast, reliable analytical methods has made possible the qualitative and quantitative assessment of technetium species generated by the radiolabeling process. Labeling stability is determined by competition of the Tc-99m-antibody bond with three ligands, Chelex 100 (a metal chelate-type resin), free DTPA solution and 1% HSA solution.Very good Tc-99m-antibody stability is obtained with activated IgG (IgGa) and Fab' fragment, which makes these substances possible candidates for immunoscintigraphy use.