Multiple sclerosis (MS), a leading cause of physical disability in young adults, is a chronic autoimmune neuroinflammatory disease characterized by axonal injury and demyelination. In this study, denaturational heat capacity profiles of blood plasma from MS patients were recorded by DSC and used to monitor the effect of therapeutic plasma exchange. The results brought out certain, so far unknown correlations of the MS clinical status with the plasma heat capacity profiles and protein oxidation levels. Severe MS cases were accompanied by remarkably large deviations of the heat capacity profiles from the norm, manifested, in particular, in a strong suppression of the albumin peak. These deviations appear to result, at least partially, from plasma protein oxidation. Sequential plasma exchange procedures shifted plasma thermograms and protein oxidation levels towards norm, implying a beneficial plasma exchange effect. An indicator of the MS severity and plasma exchange effects based on the albumin denaturation enthalpy was introduced.