Sheep Erythrocyte Preparation for Hemolytic Tests Exploring Complement Functional Activities.

Sheep erythrocytes (SE) are commonly used in complement functional tests. Non sensitized SE are useful to study the FH activity of cell protection. Indeed, as the cell surface of sheep erythrocytes is rich in sialic acids, Factor H (FH) is able to bind on it and therefore they represent a model of nonactivating surface. Because of their high capacity of complement regulation SE need to be modified to explore other functionality of the complement pathways, like the Complement hemolytic 50 (CH50) or the AP C3 convertase decay assays. For these tests, SE are sensitized with an anti-sheep red blood cell stroma antibody. In presence of serum or plasma complement components, sensitized SE may initiate complement cascade activation via the classic pathway explored in the CH50 assay. Sensitized SE may also be used to prepare C3b-coated SE that, with the use of buffers favoring AP, are suitable for the C3 Nef hemolytic assay and for the hemolytic assay studying the AP decay activity of FH. In this chapter we describe how to prepare SE for these different hemolytic tests.

Temporal correlation between serum CH50 level and symptom severity of myasthenia gravis during eculizumab therapy.

The correlation between serum 50 % hemolytic complement (CH50) level and myasthenic symptom severity has not been known in patients with anti-acetylcholine receptor (anti-AChR)-positive myasthenia gravis (MG) during eculizumab treatment. A patient with anti-AChR-positive MG showed severe bulbar symptoms. Eculizumab administration decreased CH50 level and improved the symptoms. However, shortly after the second administration of eculizumab was postponed due to the development of pneumonia, his serum CH50 level returned almost to the level it was at before the initiation of eculizumab therapy and myasthenic symptoms worsened. Even after his pneumonia was completely cleared in response to an antibiotic, the severe myasthenic symptoms persisted. After eculizumab was resumed, serum CH50 level was reduced to below the limit of detection within 24 h, and the symptom steadily improved. His symptom severity was correlated temporally with serum CH50 level during eculizumab therapy. Our case suggests that serum CH50 level may be a marker of eculizumab-induced complement blockade and an indicator of a potential worsening of myasthenic symptoms during eculizumab treatment.