Ultrastructural study of human IgG and IgG-IgM crystalcryoglobulins.

Thirty human cryoglobulin precipitates obtained from 21 patients were fixed and examined by electron microscopy; following biochemical isolation and identification. This study showed that the fine structure of cryoprecipitates depends on the involved immunoglobulins and on their respective quantities. Monoclonal IgG kappa 1 or 3 cryoglobulins with antibody activity form crystalling precipitates of 22-nm diameter rods and annuli. When polyclonal, they form 6-nm-wide filaments. Mixed IgG and IgM cryoprecipitates appear as cylindric and annular bodies with an internal diameter of 12 nm and a total diameter of 62 nm. When IgM predominates over IgG, globular condensations with a diameter of 30 nm are seen. Mixtures in which the IgG is more abundant than the IgM include fingerprint-like periodic condensations.