Some factors affecting precipitation and complex formation of an IgG cryoglobulin.

A patient with a monoclonal IgG kappa cryoglobulin presented with the purpura-arthralgia syndrome but showed no evidence of plasma cell myeloma. Cold exposure provoked hypocomplementaemia and increased urinary histamine excretion. A papular lesion provoked by cold exposure showed a vasculitis type lesion on biopsy. The cryoglobulin had a higher sedimentation rate, twice as many sulphydryl groups and a markedly lower content of sialic acid, than the non-cryo IgG from the same patient. On cryoprecipitation the monoclonal cryoglobulin preferentially interacted with autologous non-cryo IgG forming intermediate type, 9S IgG–11S IgG complexes. This was thought to depend in part on rheumatoid factor activity of the cryoglobulin. The effect on cryoprecipitation of various low molecular weight substances was studied.