113 - Guidelines for cryoglobulin research
Autor(s): M. Ruggeri, I. Brusca, F. Bottan, B. Milanesi, L. Cinquanta, M. Tani, S. Mangraviti,C. Ottomano, M. Gallina
Issue: RIMeL - IJLaM, Vol. 6, N. 3-S1, 2010 (MAF Servizi srl ed.)
Page(s): 113-116
Cryoglobulins are a group of proteins with the commonproperty of forming precipitates when the serum is keptat 4 °C, and then returning to solution when re-heated at37 °C. They may be found as different immunoglobulin(Ig) isotypes in many diseases. After being purified andpassed through an immunochemical process, cryoglobu-lins can be classified as single or mixed.According to the Brouet classification cryoprecipitates areestablished by:- cryoglobulinemia type I: a single complete monoclonalIg (IgG, IgA,IgM) or more rarely by a single light chain. Itcan be found in patients affected by lymphoproliferativedisease, multiple myeloma, Waldenstrom’s macroglobuli-nemia.- cryoglobulinemia type II: a monoclonal IgM and apolyclonal or oligoclonal IgG, linked to lymphoprolife-ractive diseases, autoimmune illnesses or HCV infection.- cryoglobulinemia type III: polyclonal IgG, IgA and IgM,found in patients with autoimmune diseases and chronicinfections.The cryoglobulin result is strictly method dependent. Blo-od is collected without anticoagulant, using a pre-heatedneedle at 37 °C and kept at this temperature until bloodcoagulates. The serum is then separated by centrifugationat 37 °C at 800g for 15 minutes. It is then aliquoted anddispensed into a plain tube and a Wintrobe tube that arekept at 4 °C. Cryoglobulates, if present, will appear after24-72 hours as white precipitates or gel. They, howevermust be kept under observation for at least one week sothat any late cryoglobulin can be noticed. After centrifuga-tion, the amount of cryoglobulin is measured by the per-centage level of cryoprecipate in the Wintrobe tube.Cryoglobulins can be then classified by immunofixationusing total and specific human anti-sera (γ,α,µ,κ,λ). In thepresence of cryoglobulinemia, the laboratory reports shouldinclude the cryocrit, the Ig isotype, and the clonality (mono-or polyclonal), according to the Brouet classification.Key-words: HCV, mixed cryoglobulinemia, immune com-plexes, immunoglobulins, rheumatoid factor.