[Monoclonal immunoglobulins and serum viscosity: contribution of the idea of activation energy to the paraprotein concept (author's transl)].

The simultaneous study of dynamic and cinematic viscosity in 34 control sera and 49 paraprotein sera showed that there was a simple relationship between the viscosity and the total serum protein content both in normal sera and in paraprotein sera. When the ratio of monoclonal immunoglobulins/total proteins is less than 55%, the viscosity is little or not modified in the case of the IgGk paraproteins studied, whereas it was increased in the case of IgA, IgM and IgG LAMBDA SERA. Beyond 2 cSt, it is not however possible to incriminate a particular type of heavy chain nor even a light chain. The measurement of the viscosity in relation to the temperature permitted us to show that the IgA, IgG, and IgM sera studied all presented an activation energy of outflow (E in Kcal) higher than that of normal sera and the highest rise is due to IgA paraproteins. The concept of energy activation permits us to say that paraproteins have a different behaviour from normal proteins, probably due to disorders in their structural arrangement.