Initiation of systemic autoimmunity and sequence specific anti-DNA autoantibodies.

Antibodies to double-stranded DNA (dsDNA) are a defining feature of Systemic Lupus Erythematosus (SLE). The molecular characterization of anti-dsDNA autoantibodies reveals that they are actively selected for binding to antigen. Evidence for antigen selection includes the use of suitable rearrangement products, the switching of IgM isotype to IgG, and the acquisition of somatic mutations that raise the affinity for dsDNA. Through a process of specificity maturation, anti-dsDNA antibodies can arise from anti-single stranded DNA (ssDNA) antibodies that also occur in nonautoimmune individuals. To clarify circumstances leading to the initiation of systemic autoimmunity, we compare features of immune responses to nucleic acids that operate before and after disease develops. Evidence indicating that anti-dsDNA antibodies bind with DNA sequence preference is highlighted to propose that sequence-specific anti-dsDNA antibodies may be induced by an infectious agent and in turn may extend the response to endogenous nuclear antigens. Thus, sequence-specific anti-dsDNA B cells may provide an important stimulus to break the tolerance to self.

A monoclonal antibody, 3A10, recognizes a specific amino acid sequence present on a series of developmentally expressed brain proteins.

Immunoblotting showed that a monoclonal antibody, 3A10, binds to a series of rat brain-specific antigens with molecular masses of 150-, 120-, 118-, 106-, 104-, 79-, and 77-kDa. The expression of 3A10 antigens is dependent on the developmental stage of the brain; only the 106-kDa antigen is detected during embryonic stages of rat brain development, while the expression of the remaining 6 antigens starts after birth and reaches a maximum during postnatal days 15-21. Detection of the 3A10 antigens in cultured neuronal and glial cells derived from cerebral cortices of rat brain at embryonic day 18 showed that the 77-, 79-, 106-, and 150-kDa antigens are specifically expressed in neuronal cells. The 77-kDa antigen was purified and identified as synapsin I by amino acid sequence analyses of the peptide fragments isolated after Achromobacter protease I treatment. During the isolation of 3A10-reactive proteins by immunological screening of cDNA libraries constructed from adult rat brain, we found that all of the 3A10-reactive clones contain nucleotide sequences encoding the unique amino acid sequence TRSP(S, R,G)P. Analyses of 3A10-binding to various synthetic peptides showed that the monoclonal antibody recognizes a specific conformational structure formed by either the TRSPXP sequence or similar amino acid sequences that are expressed on a series of developmentally expressed brain proteins.

Helical epitopes determined by low-stringency antibody screening of a combinatorial peptide library.

Combinatorial phage display peptide libraries are routinely used to map epitopes of specific monoclonal antibodies. In this study we illustrate that these libraries can be used in the analysis of protein structure. By screening libraries at low stringency, a collection of phages can be obtained. These are characterized by the fact that they are recognized by a given monoclonal antibody yet with various affinities. Comparing the random peptides of these phages indicates the common essential residues necessary for antibody recognition. Aligning the inserts based on the detected homology has revealed structural motifs that correspond to secondary protein structures. The envelope protein of HIV-1 has been studied using this approach. A combinatorial phage display library containing a 20 mer random peptide in protein III of the filamentous phage fd-tet has been used to analyze two different monoclonal antibodies directed against gp120. Our results provide experimental evidence that indicate that the C1 domain of gp120 contains an alpha helix.

Um antígeno espécie e estágio-específico para o schistosoma haematobium. Identificaçäo através de anticorpos monoclonais a partir de imunizaçäo de camundongos Balb/C com antígenos ovulares solúveis / Species-specific-antigens for schistosoma-haematobium: Identification by monoclonal antibodies produced of Balb/C mice immunized with soluble egg antigens

No presente estudo, relata-se a identificaçäo e caracterizaçäo imunoquímica parcial de antígenos específicos do Schistosoma haematobium reconhecidos através de anticorpos monoclonais murinos. Os anticorpos monoclonais foram produzidos em camundongos Balb/C imunizados com antígenos ovulares solúveis por via intraperitonial. Este trabalho contribui para a identificaçäo de antigenos do S. haematobium que säo espécie-específicos e que tambem só foram detectados nos ovos dos parasitas, sendo também estágio-específicos. A comparaçäo da sequência parcial de aminoácidos de dois peptídeos tripticos de banda antigenica reconhecida pelo anticorpo monoclonal 2D14E8 em membrana de nitrocelulose com outras sequências de proteínas conhecidas revelou, nos dois peptídeos, uma homologia com a proteína "heat-shock" ou proteína de estresse 70 presente em várias espécies animais, incluindo o homem e o S. mansoni