Robert S. Greenfield

ADAMTS13-binding IgG are present in patients with thrombotic thrombocytopenic purpura.

Functional assays are commonly used to measure the antibodies of ADAMTS13 found in patients of thrombotic thrombocytopenic purpura (TTP). In this study we used an enzyme-linked immunoassay to analyze the ADAMTS13-binding IgG levels in six groups of individuals: normal, random hospitalized patients, acute TTP, TTP after receiving plasma therapy, TTP in remission, and other types of thrombotic microangiopathy (TMA). The results showed that ADAMTS13-binding IgG levels were elevated in 100% of the acute TTP group, 75% of the TTP group after receiving plasma therapy, and 40% of the remission group. Overall, the ADAMTS13-binding IgG levels correlated with the inhibitory activity levels againstADAMTS13 (r = -0.69, P < 0.0001). The assay also detected elevated IgG binding levels in 5% - 15% of the normal, random, and other TMA control groups. Addition of purified ADAMTS13 protein to the plasma samples suppressed the IgG binding in each of the acute TTP patients, but in none of the non-TTP groups. Serial measurement in a patient that had two exacerbations of TTP within the first three weeks revealed that the ADAMTS13 activity levels remained <0.1 U/ml during this period, and the ADAMTS13-binding IgG remained elevated, suggesting that ADAMTS13 analysis may provide valuable insight to the disease status during the course of therapy. Analysis of ADAMTS13-binding IgG is helpful for the diagnosis and management of TTP.

Seminal thrombin-activatable fibrinolysis inhibitor: a regulator of liquefaction.

Several active components of the haemostatic system have been identified in human semen. Here we investigated the presence of thrombin-activatable fibrinolysis inhibitor (TAFI) in seminal plasma. Using an enzyme-linked immunosorbent assay, TAFI levels were measured in 36 semen specimens obtained from subfertile, normally fertile, fertile sperm donor and vasectomized individuals. TAFI was detectable in human semen. Its levels were highest in vasectomized individuals compared with the other groups, including a pooled normal semen parameter stratification group (by World Health Organization criteria). This elevation in the vasectomy group was found to be statistically significant in comparison with the normally fertile (P < 0.01) and the pooled normal semen parameter groups (P < 0.05). Seminal TAFI levels showed a significant positive correlation with total sperm count and sperm density. In contrast, a negative association was observed with semen volume, days of sexual abstinence and liquefaction time. The highly motile sperm group showed low TAFI levels. Our results establish the presence of TAFI in seminal plasma with a probable role in the protection of the seminal clot against lysis. It also suggests a downstream (post-testicular) source for its production. This reinforces the involvement of the conventional haemostatic system in the coagulation and liquefaction properties of human semen.

Detection and quantification of thrombomodulin in human semen.

The presence of fibrin degradation products, thrombin-like enzyme, prothrombin fragments, thrombin-activatable fibrinolysis inhibitor, plasmin and other active components of blood coagulation and fibrinolysis in seminal plasma has been reported. In the present study we investigate the presence of thrombomodulin in human semen. Using an Imubind thrombomodulin enzyme-linked immunosorbent assay (American Diagnostica Inc., Stamford, Connecticut, USA), seminal thrombomodulin levels were measured in 47 semen specimens obtained from subfertile individuals, normally fertile individuals, semen donors as well as vasectomized individuals, and in a further group defined by normality in several parameters derived from the World Health Organization fertility criteria. Conventional semen parameters were analysed in all semen samples. Thrombomodulin is quantifiable in human semen at a concentration lower than that normally found in citrated blood plasma samples. Slightly higher levels were seen for fertile stratifications compared with infertile individuals but without significant difference, given the numbers accrued. A vasectomized group showed the lowest value. In conclusion, our results establish the presence of thrombomodulin in human semen and suggest its production both upstream and downstream from the level of a vasectomy lesion.