Chemical and genetic characterization of a monoclonal IgA(lambda) protein with both cryo- and pyro-precipitability.

Studies of a monoclonal IgA (lambda) protein with both cryo- and pyro-precipitability show that it belongs to the IgA2 subclass and is positive for the A2m(2) allotypic marker. Like other cryoglobulins, this protein also has an unblocked light chain, and its heavy chain belongs to the VHI subgroup. The first 22 N-terminal amino acids of the lambda chain of this protein showed less than 65% homology with those of other human lambda chains but showed 86% identity with that of an amyloid fibril protein reported by others. The alpha chain of this protein appears to have more glutamic acid or glutamine, or both, and less isoleucine residues than other human alpha chains.