Rabbit antibodies against small peptides may be composed by subpopulations recognizing different epitopes made likely by few amino acids. This explains the frequent crossreactivity of antipeptide antibodies with unrelated peptides. A suitable use of immunoadsorbents is suggested to obtain truly specific antibodies able to react with restricted amino acid sequences.

Animals↗

PubMedDate not supplied

Recognition of HLA class II molecules by antipeptide antibodies elicited by synthetic peptides selected from regions of HLA-DP antigens.

Repeated immunizations of rabbits with chemically synthesized peptides from selected regions of HLA-DP histocompatibility antigens resulted in the production of specific antibodies that were then isolated from the immune sera by chromatography on Sepharose-peptide immunoadsorbents. The purified antibodies, when tested with an enzyme-linked immunosorbent assay, specifically bound to the inciting fragments; moreover, two of them recognized glycoproteins extracted by nonionic detergents from human chronic lymphocytic leukemia cells, as revealed by binding assays. The results suggest that amino acid stretches 51-61 of the alpha chain and 80-90 of the beta chain of HLA-DP histocompatibility antigens are likely exposed on the surface of the protein molecule. The specific recognition of DP regions is strongly suggested by the difference in the binding of those antibodies to soluble membrane proteins, as compared to the binding of monomorphic anti-Class II monoclonal antibodies to the same antigens.

Amino Acid Sequence↗

PubMedDate not supplied

Do monoclonal antibodies recognize linear sequential determinants?

A group of 19 anti-class II monoclonal antibodies produced in different laboratories were tested in ELISA for their ability to bind to a panel of synthetic peptides selected from HLA-DQ alpha and beta chains. No one of the antibodies tested was found to react with the synthetic fragments, thus confirming the common finding that MoAbs generally fail to recognize fragments of the native antigen. The possibility that this result might be partly due to the procedure used for screening hybridoma supernatants is discussed.

Antibodies, Monoclonal↗

PubMedDate not supplied

Preparation and isolation of antibodies to human MHC class II alpha chains by aid of synthetic peptides.

Antibodies against HLA Class II alpha chains were prepared by using as immunogens synthetic peptides selected from the HLA-DQ1 alpha chains sequence. Antibodies raised against peptide E2, a 15-residue fragment of the polymorphic first domain, reacted preferentially with cells with the DQ1 phenotype; however, despite the low sequence homology of this fragment with corresponding segments in DQw2 and DQw3 alpha chains, a partial crossreactivity with cells not expressing the DQw1 specificity was detected. Antibodies to peptide H, selected from the monomorphic frame, might be specific for DQ alloantigens, and presumably do not react with DR antigens. The two peptides, in addition, bind anti-Class II antibodies from the serum of a rabbit immunized with human cells, and appear to represent immunogenic linear determinants in the native glycoprotein molecule.

Amino Acid Sequence↗

PubMedDate not supplied

Specificity of anti-MHC class II antibody binding to synthetic peptides.

This study indicates that antibodies raised against a DR4,w6; DQw1,3 positive cell line may bind to synthetic peptides selected from the polymorphic amino acid sequences 51-59 and 63-79 on the DQw2 beta chain. This cross-reaction may be explained by the relatively high sequence homology of these sequences in the beta chains of class II histocompatibility antigens, and suggests that antibody binding to small peptides may be scarsely selective. Based on the observations of the reactivity of the antibodies with several cell lines, and comparison of the amino acid sequences of beta chains of DR and DQ molecules, an attempt to identify the cross-reacting epitope is presented.

Amino Acid Sequence↗