Monitoring of multiple sclerosis (MS) requires of molecular markers. Recently, using TCA-precipitation/ extraction and MALDI TOF/TOF mass-spectrometry, we identified in blood serum of multiple sclerosis (MS) patients earlier unknown 46 kDa form of human unconventional myosin IC isoform b (Myo1C) (Myronovskij et al., 2015). During SDS-electrophoresis of TCA-extracted proteins of blood serum of 28 MS patients, 3 additional polypeptides with 55, 50 and 25 kDa molecular masses were detected. Western-blot analysis using monospecific anti-human IgG rabbit HRP-conjugated antibodies showed that 55 and 25 kDa polypeptides belong to heavy and light chains of IgG molecules, while 50 kDa protein corresponds to free heavy chains of IgGs. None of these polypeptides was found in fractions of TCAextracted polypeptides isolated from blood serum of healthy human donors or patients with systemic lupus erythematosis and rheumatoid arthritis.