Do infections induce monoclonal immunoglobulin components?

The incidental finding of monoclonal immunoglobulin components (MC) in some infections prompted us to study this phenomenon more systematically. Using isoelectric focusing with immunoblotting (detection limit for MC 0.1 mg/ml), the following infections were studied for the presence of MC: visceral leishmaniasis, cytomegalovirus (CMV) infection, echinococcosis and infectious mononucleosis. MC were found in 16 of 20 leishmania patients and in eight of 18 CMV patients, but in only one of 20 echinococcosis patients and in none of 30 infectious mononucleosis patients. The MC were mostly transient, where tested. A minority of the MC found in the leishmaniasis patients was shown to bind to leishmania antigens. The specificity of the majority of the MC remains unknown. Further study is required to explain the high incidence of MC in CMV infection and visceral leishmaniasis.