title: Antigenic specificity and expression of a natural idiotope on human pentameric and hexameric IgM polymers.
abstract: Natural antibodies (NAbs) are present in circulation even before the exposure to antigen and they exert various biological functions. They are polyreactive and mainly represented by immunoglobulin M (IgM), which is the first antibody produced in an ongoing immune response to infection and/or immunization. IgM is always secreted as a polymer with predominant pentameric structure, although other polymeric forms such as hexamer can be also formed. The biological functions of hexameric IgM are still not known and it is proposed that its existence as a NAb could be deleterious. However, the nature of IgM hexamers has not been investigated yet. In this paper, we have tested the expression of natural idiotope and antigenic specificities of pentameric and hexameric IgM polymers originating from sera of patients with Waldenström's macroglobulinemia, as well as patients suffering from recurrent urinary bacterial infections. We demonstrate that although pentameric IgM polymers can exist as natural and immune antibodies, IgM hexamers are exclusively immune and do not exist as NAbs.
authors.affiliation: Department of Research and Development, Institute of Virology, Vaccines and Sera-Torlak, Vojvode Stepe 458, 11221 Belgrade, Serbia. vzpetrusic@gmail.com
authors.forename: Vladimir
authors.initials: V
authors.lastname: Petrušić
authors.forename: Irena
authors.initials: I
authors.lastname: Zivković
authors.forename: Marijana
authors.initials: M
authors.lastname: Stojanović
authors.forename: Ivana
authors.initials: I
authors.lastname: Stojićević
authors.forename: Emilija
authors.initials: E
authors.lastname: Marinković
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Inić-Kanada
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Dimitijević
mesh_terms: D000918:Antibody Specificity / Q000276:immunology*; D001437:Bacteriuria / Q000097:blood / Q000150:complications / Q000276:immunology* / Q000382:microbiology; D005260:Female; D006801:Humans; D007144:Immunoglobulin J-Chains / Q000097:blood / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology*; D008297:Male; D055503:Protein Multimerization / Q000276:immunology*; D008258:Waldenstrom Macroglobulinemia / Q000097:blood / Q000150:complications / Q000276:immunology* / Q000382:microbiology
chemical_list: D007144:Immunoglobulin J-Chains; D007075:Immunoglobulin M