An immunochemical method for quantitative determination of latent antithrombin, the reactive center loop-inserted uncleaved form of antithrombin.

• Antithrombin (AT) is a serine protease inhibitor that has thrombin, factors IXa and Xa as target proteases. In addition to active native AT, two other forms have been identified in plasma: the reactive center loop inserted cleaved and latent, uncleaved forms. Both have been shown to be present in normal human blood. Latent AT forms a dimer with native AT in vitro, thus inactivating the native form. Here we describe a mouse monoclonal antibody, 8C8, that is specific for latent AT. The affinity of 8C8 was found to be 500-fold higher for latent than for native AT and 5000-fold higher for latent than for cleaved AT. A sandwich assay was developed to measure the concentration of latent AT in plasma, which was found to be similar to 4.8 mg L-1 in healthy individuals. The K-D of the interaction between native and latent AT was found to be 51 mu M, i.e. far above the plasma concentration of both native and latent AT, indicating a negligible complex formation in blood.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kardiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cardiac and Cardiovascular Systems (hsv//eng)

Nyckelord

latent antithrombin

immunochemical sandwich assay

antithrombin

monoclonal antibody

native-latent antithrombin dimer

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