Isolation and functional assay of the membrane complement inhibitors CD55 (DAF) and CD59 (MIRL)

The interaction between the complement system and hemostatic factors

PURPOSE OF REVIEW

To discuss the crosstalk between the complement system and hemostatic factors (coagulation cascade, platelet, endothelium, and Von Willebrand Factor), and the consequences of this interaction under physiologic and pathologic conditions.

RECENT FINDINGS

The complement and coagulation systems are comprised of serine proteases and are genetically related. In addition to the common ancestral genes, the complement system and hemostasis interact directly, through protein-protein interactions, and indirectly, on the surface of platelets and endothelial cells. The close interaction between the complement system and hemostatic factors is manifested both in physiologic and pathologic conditions, such as in the inflammatory response to thrombosis, thrombosis at the inflamed area, and thrombotic complications of complement disorders.

SUMMARY

The interaction between the complement system and hemostasis is vital for homeostasis and the protective response of the host to tissue injury, but also results in the pathogenesis of several thrombotic and inflammatory disorders.

Paroxysmal nocturnal haemoglobinuria: to prednisone or not to prednisone?--a case report of a patient previously treated with steroids for 15 yrs and significant response on eculizumab

BACKGROUND

Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired haematopoietic stem cell disorder characterised by persistent haemolysis and platelet activation, severe end-organ damage, an increased risk of thrombosis and early mortality. We present the case of a 56-year-old male with long-standing PNH and significant disease-related morbidity who underwent steroid therapy for approximately 15 yrs before treatment with eculizumab, a humanized monoclonal antibody that blocks the terminal phase of the complement cascade at the C5 level.

CASE HISTORY

The patient presented with a severely impaired quality of life in 1997 and was diagnosed with PNH 8 months later, soon after which he was commenced on steroid therapy with prednisone. During long-term steroid therapy with progressive increases in prednisone dose, the patient had frequent haemolytic episodes as well as thrombosis and renal complications. He also experienced Cushing's syndrome with arterial hypertension, insulin-dependent diabetes mellitus, osteoporosis, acne and portal fibrosis. Eculizumab therapy was started in late-2009 and led to rapid improvements in haemoglobin and lactate dehydrogenase levels with a complete cessation of haemolytic episodes. Eculizumab has been well tolerated.

CONCLUSIONS

Long-term steroid therapy was not effective in controlling PNH in this patient and was associated with significant comorbidities. Treatment with eculizumab led to major improvements, even after such a long period with relatively uncontrolled disease.

An inter-laboratory comparison of PNH clone detection by high-sensitivity flow cytometry in a Russian cohort

OBJECTIVES

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal stem cell disorder characterized by partial or absolute deficiency of glycophosphatidyl-inositol (GPI) anchor-linked surface proteins on blood cells. A lack of precise diagnostic standards for flow cytometry has hampered useful comparisons of data between laboratories. We report data from the first study evaluating the reproducibility of high-sensitivity flow cytometry for PNH in Russia.

METHODS

PNH clone sizes were determined at diagnosis in PNH patients at a central laboratory and compared with follow-up measurements in six laboratories across the country. Analyses in each laboratory were performed according to recommendations from the International Clinical Cytometry Society (ICCS) and the more recent 'practical guidelines'. Follow-up measurements were compared with each other and with the values determined at diagnosis.

RESULTS

PNH clone size measurements were determined in seven diagnosed PNH patients (five females, two males: mean age 37 years); five had a history of aplastic anemia and three (one with and two without aplastic anemia) had severe hemolytic PNH and elevated plasma lactate dehydrogenase. PNH clone sizes at diagnosis were low in patients with less severe clinical symptoms (0.41-9.7% of granulocytes) and high in patients with severe symptoms (58-99%). There were only minimal differences in the follow-up clone size measurement for each patient between the six laboratories, particularly in those with high values at diagnosis.

CONCLUSIONS

The ICCS-recommended high-sensitivity flow cytometry protocol was effective for detecting major and minor PNH clones in Russian PNH patients, and showed high reproducibility between laboratories.