Monoclonal cryoimmunoglobulin with anti-cytomegalovirus activity associated with T cell chronic lymphocytic leukaemia.

A patient with chronic T cell lymphocytic leukaemia developed a monoclonal immunoglobulin (IgG3 kappa = 14 g/l) which was in part cryoprecipitable. At the same time, a subclinical CMV infection occurred which was associated with a neutropenia and thrombocytopenia, and which led to a rise in anti-CMV antibodies. The F(ab')2 fragment of IgG3 kappa, obtained by enzymatic cleavage, was examined for several antiviral activities and it was found to have a strong anti-CMV activity using the immunofluorescence test with anti-kappa conjugate. This is one of the few examples of a cryoglobulin with specific antiviral activity. The leukaemia, possibly together with immunosuppressive therapy, may have been responsible for the uncontrolled proliferation of the clone producing the cryoimmunoglobulin.