Specimen Information

Type

Gold, SST

Volume

3.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

CRITICAL FROZEN – Separate samples must be submitted when multiple tests are ordered

Fasting Required?

False

Clinical Significance

Many autoimmune disorders, chronic infections and malignancies are associated with circulating immune complexes. Quantitation of immune complexes assists in staging immunologic disorders. Immune complexes bind to Raji Cells via their complement receptors. The immunoglobulin portion of the immune complex is then detected by flow cytometry with anti-human IgG-FITC.

A variety of diseases are associated with circulating immune complexes (CIC). Quantitation of CICs assists in staging immunological disorders. CICs are formed by the interaction of antibodies with specific antigen. This normal process of the immune response results in the rapid clearance of CICs by the reticuloendothelial system. However, in some cases there is desposition of CICs in tissues with associated inflammatory-mediated damage. Elevated CICs have been detected in a variety of autoimmune diseases (e.g., systemic lupus erythematosus [SLE], rheumatoid arthritis [RA], etc.), certain cases of glomerulonephritis, infectious diseases (e.g., Lyme disease, chronic HBV infection, HIV infection, endocarditis, etc.), and some malignancies. Some authors believe that immune complex determinations may be useful in monitoring disease activity in certain autoimmune disorders, particularly RA and SLE. A positive CIC assay, however, does not necessarily implicate immune complexes in disease pathogenesis, nor does it necessarily correlate well with disease activity. There are two general categories of CICs: antigen-specific (e.g., to HBsAg) and antigen-nonspecific. In most clinical circumstances, the nature of the specific antigen is unknown. Therefore, most assays are designed to detect antigen-nonspecific CICs. These include Raji cell, C1q binding, conglutinin, and anti-C3 assays. Immune complex detection with Raji cells and flow cytometry is sometimes preferred by clinicians over other available assays. In the Raji cell assay, CICs bind to cell-associated complement receptors and are then detected by flow cytometry with fluorescein isothiocyanate (FITC)-labeled anti-human IgG. Raji cell CICs have been particularly noted in patients with necrotizing systemic vasculitis and in sarcoidosis.