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Abstract
Intact immunoglobulin molecules contain unique junctional epitopes across the heavy chain and light chain constant regions that are the target of heavy + light chain isotype assays (Hevylite, HLC). HLC assays quantify the different light chain types of each immunoglobulin class, i.e. IgGκ, IgGλ, IgAκ, IgAλ, IgMκ and IgMλ. These molecules are measured in pairs, e.g. IgGκ/IgGλ, to produce ratios in the same manner as serum free light chain κ/λ ratios. As with Freelite® sFLC immunoassays, polyclonal antibodies raised in sheep provide the most attractive method of recognizing polymorphic immunoglobulin molecules. There are theoretically four HLC epitope regions per immunoglobulin molecule - one on each side of each heavy/light chain contact region. Multiple HLC epitopes enable immune complexes to form readily, allowing homogeneous immunoassays to be produced that are suitable for turbidimeters.
The main clinical applications of serum free light chain and Hevylite® measurements are for patients with monoclonal gammopathies.
This article presents an overview of the use of sFLC and HLC measurements in MM and related disorders; from pre-malignant MGUS and smoldering multiple myeloma (SMM), to the symptomatic disorders MM and others.
References
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