Native PAGE analysis followed by immunoblotting indicated that Phe229Leu AT spontaneously polymerized in the proband's plasma. (A) AT migration profile with a control plasma (lane 1), a heterozygous parent (lane 2), and the homozygous proband (lane 3) compared with purified human latent AT (lane 4), native AT (lane 5), and heat-polymerized AT (lane 6). (B) Analysis of the proband's plasma sampled after (lane 1) and during (lane 2) the sepsis-associated thromboembolic event; note the fall in the monomeric AT species during the acute phase.