Technetium-99m-labeled proteins for imaging inflammatory foci.

Polyclonal human IgG (IgG), antinuclear antibody (TNT-1), and human serum albumin (HSA), were labeled with 99mTc by a method recently developed in our laboratory, and administered i.v., each to a separate group of five mice, bearing inflammatory foci induced by an i.m. injection of 40 microL turpentine or 5 x 10(8) E. coli and 5 x 10(8) Entercocci. TNT-1 labeled with 125I served as a control and 67Ga-citrate as a "gold standard". At 4 or 24 h post injection, animals were imaged and sacrificed for tissue distribution studies. At 4 h in the turpentine group, the abscess-to-muscle ratios were: 67Ga, 4.8 +/- 2.1, 125I-TNT-1, 4.3 +/- 1; 99mTc-TNT-1, 3.5 +/- 1.8; 99mTc-IgG, 3.9 +/- 0.6; and 99mTc-HSA, 4.3 +/- 1. In the microorganism group, these ratios were 2.6 +/- 0.6, 3.3 +/- 0.5, 3.4 +/- 0.08, 3 +/- 1.1 and 4.1 +/- 0.6, respectively. Autoradiographic examination of infected tissues indicated that leakage of labeled proteins into interstitial space due to increased capillary permeability may be one of the major mechanisms of uptake.