Catalytically active artificial and natural antibodies (Abs) or abzymes (Abzs) have been studied intensively (see reviews [1][2][3][4][5][6][7]). The first example of a natural Abz was an IgG found in bronchial asthma patients which hydrolyzes intestinal vasoactive peptide (VIP) [8], the second was an IgG with DNase activity in SLE [9], and the third was an IgG with RNase activity in SLE [10].Catalytic IgGs and/or IgMs hydrolyzing RNA and DNA [9][10][11][12][13][14][15][16][17], polysaccharides [18][19] or peptides and proteins [20][21][22][23][24][25] AbstractVarious catalytic antibodies or abzymes have been detected recently in the sera of patients with several autoimmune pathologies, where their presence is most probably associated with autoimmunization. Recently we have shown that DNase, RNase, and polysaccharide-hydrolyzing activities are associated with IgGs from the sera of patients with multiple sclerosis (MS). Here we present evidence demonstrating that highly purified MS IgGs (but not Igs from the sera of healthy individuals) catalyze specifically hydrolysis of human myelin basic protein (hMBP). In contrast to many known proteases, IgGs do not hydrolyze many other different proteins. Specific inhibitors of acidic and thiol proteases have no remarkable effect on proteolytic activity of IgGs. However, specific inhibitor of serine (PMSF, AEBSF, and benzamidin) and metal-dependent (EDTA) proteases significantly inhibit activity of proteolytic abzymes. Interestingly, the ratio of serine-like and metal-dependent activities of MS IgGs varied very much from patient to patient. The findings speak in favor of the generation by the immune systems of individual MS patients of a variety of polyclonal anti-MBP IgGs with different catalytic properties.

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Human myelin basic protein (hMBP)-hydrolyzing activity was recently shown to be an intrinsic property of antibodies (Abs) from multiple sclerosis (MS) patients. Here, we present the first evidence demonstrating a significant diversity of different fractions of polyclonal IgGs (pIgGs) from MS patients in their affinity for hMBP and in the ability of pIgGs to hydrolyze hBMP at different optimal pHs (3–10.5). IgGs containing λ- and κ-types of light chains demonstrated comparable relative activities in the hydrolysis of hMBP. IgGs of IgG1–IgG4 sub-classes were analyzed for catalytic activity. IgGs of all four sub-classes were catalytically active, with their contribution to the total activity of Abzs in the hydrolysis of hMBP and its 19-mer oligopeptide increasing in the order: IgG1 (1.5–2.1%) < IgG2 (4.9–12.8%) < IgG3 (14.7–25.0%) < IgG4 (71–78%). Our findings suggest that the immune systems of individual MS patients generate a variety of anti-hMBP abzymes with different catalytic properties, which can attack hMBP of myelin-proteolipid shell of axons, playing an important role in MS pathogenesis.