C3b Deposition Assay

Thrombotic microangiopathy (TMA) describes a group of life-threatening multi-systemic diseases characterized by microvascular thrombosis, consumptive thrombocytopenia and microangiopathic hemolytic anemia, often leading to renal failure, cerebral ischemia and end-organ damage.  While TMAs are often caused by infections, cancers, pregnancy, drugs, trauma, malignant hypertension and cobalamin deficiency, complement-mediated TMAs, such as atypical hemolytic uremic syndrome (aHUS) are triggered by over-activity of the complement alternative pathway on the cell surface.  We have developed a simple, reliable and quick method to detect C3b deposition secondary to fluid-phase complement dysregulation.  Images are numerically scored (normal, 1+ to 5+) using predesignated images (refer to C3 Deposition images below).

Indications for screening
Screening is appropriate only for patients with aHUS.

MORL screening methodology
C3b deposition measures complement-mediated C3b deposition on cell surfaces secondary to activation of the alternative pathway (AP).  Briefly, patient sera is diluted in AP activation-permissive buffer and added to cultured MES-13 cells which are incubated at 37°C for 20 minutes.  C3b deposition on cell surfaces is visualized using Alexa-488 labeled anti-C3 antibody (7C12).  Reference range: negative.


Turnaround time
Turnaround time is ~ 4 weeks

Sample Required
1 ml frozen serum (see testing requisition for specimen handling).

Cost & CPT Codes

The Clinical Diagnostics Service of the Molecular Otolaryngology & Renal Research Laboratories is a CLIA-approved, Joint Commission-accredited diagnostic laboratory.