Biomedical subjects

A Chersi

Publications and source records attributed to A Chersi.

82 records · Page 5Linked to original sources

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↗

PubMedDate not supplied

Partial characterization of anti-HLA class II antibodies isolated by aid of sepharose-peptide immunoadsorbents.

Synthetic peptides selected from HLA-DQ and HLA-DP glycoproteins were coupled to Sepharose, and used for the isolation of anti-HLA Class II antibodies from the immune sera of rabbits immunized with human lymphoblastoid cells expressing Class II antigens. Antibodies from early and late bleedings displayed remarkable differences in affinity for peptides and for soluable membrane proteins: these differences might be due to an early immune response directed preferentially against surface linear determinants, and to a late response to assembled (discontinuous) sites. The possibility that such antibodies might be used for the identification of amino acid stretches involved in the formation of the same assembled determinant is considered.

Animals↗

PubMedDate not supplied

Specificities of rabbit antisera to multiple antigen (MAP) peptides.

Two multiple antigen peptides consisting of 6 and 7 aminoa cid residues, respectively, plus a 12-residue fragment, used as a control, all linked to a polylysine core, were used as immunogens in rabbits in order to obtain an immune response. Rabbit antisera against such polymers were then tested in ELISA against a panel of antigens in order to analyze the specificities of the resulting antibodies. The responses were different for all three immunogens, being partially or totally directed, for two of the three compounds, including the 12-residue control MAP peptide, against the polylysyl core, which is considered as non immunogenic. The third MAP polymer was practically unable to elicit an immune response.

Amino Acid Sequence↗

PubMedDate not supplied

Definition of essential amino acid residues in the recognition of a peptide by a mouse monoclonal antibody.

A mouse monoclonal antibody reacting in ELISA with a synthetic peptide representing a linear amino acid stretch of the protein antigen was tested on all overlapping 5-mer to 9-mer fragments of the peptide, as prepared by multi-pin synthesis. Analysis of the binding data suggests that several residues in the peptide might be relatively unrelevant for recognition, while few others seem to play a critical role as key residues. On the basis of such observations, we attempted to reconstruct an alternative essential epitope by introducing multiple amino acid substitutions in the 9-mer peptide exhibiting the best binding activity, and then tested its ability to be recognized by the monoclonal antibody.

Amino Acid Sequence↗

PubMedDate not supplied

Isolation, characterization and comparison of antipeptide and antiprotein rabbit antibodies to the pi-isoform of glutathione S-transferase.

The main linear epitopes of pi-glutathione transferase (pi-GST, EC 2.5.1.18), an enzyme related to cancer progression in a restricted number of tumours, were identified by testing in ELISA the reactivities of polyclonal anti-pi-GST rabbit sera against a panel of 51 overlapping decapeptides, covering the whole 216-residue sequence of the protein. Several major reactivity peaks were detected, each covering two or three adjacent peptides. The most active fragments were then reconstructed by conventional solid-phase synthesis, linked to Sepharose, and used as affinity ligands for isolating specific anti-pi-GST antibody subsets. A second group of antisera was then prepared in rabbits by using as immunogens some of the above described synthetic fragments, linked to a carrier protein, and antipeptide antibodies purified by affinity chromatography. An ELISA test was then performed, using as antigens a panel of peptides and different isoforms of GST, in order to establish whether antibodies isolated from total anti-pi-GST sera would display higher reactivity and specificity, as compared to traditional antipeptide antibodies. Binding data clearly confirm that the formers might be indeed better reagents for the detection and possibly quantitation of pi-GST.

Amino Acid Sequence↗

PubMedDate not supplied

Flexibility of amino acid residues at position four of nonapeptides enhances their binding to human leucocyte antigen (HLA) molecules.

The binding affinity of synthetic nonapeptides to human leucocyte antigens (HLA) molecules of the A0201 allotype, the most common in Caucasian, is enhanced or reduced by suitable amino acid substitutions at position 4, as a result of increased or decreased chain flexibility. A higher flexibility of the bond at this position correlates with an easier accommodation of the fragment into the HLA groove, while rigidity of the peptide chain appears to interfere. These data are based on two lines of evidence: a) most natural high affinity ligands for HLA-A0201 possess, at position 4, flexible residues b) substitutions of such residues by rigid amino acids results in a decrease of binding affinity.

Amino Acid Sequence↗

PubMedDate not supplied

Polyclonal antibodies against gp185HER2 peptides: their putative role in the identification of a particular HER2 status in patients with breast cancer.

The HER2 oncogene and its relative oncoprotein, gp185HER2, a transmembrane glycoprotein belonging to the epidermal growth factor receptor family, are overexpressed in a wide range of solid tumors including breast and ovarian cancer. In patients with breast cancer, both humoral and cell-mediated HER2 immune responses have been found as well as in some patients with gp185HER2 nonoverexpressing tumors. To establish whether peptide sequences identified as HLA-A2-restricted T-cell epitopes are expressed in breast tumor cell lines and tissues, we produced and characterized by different methodologic approaches polyclonal antibodies raised against four gp185HER2 peptides. Two of the antibodies recognized peptides eluted from the HLA-A2 groove of the mDAmB231 breast cancer cell line expressing a basal level of gp185HER2. Paraffin-embedded primary and metastatic breast tumors were specifically immunostained by all four reagents, thereby showing an overlapping reactivity. When this immunoreactivity was compared with that obtained using two different monoclonal antibodies, in 105 breast primary tumors and 36 corresponding lymph node metastases, we identified a subset of tumors that were negative with anti-gp185HER2 monoclonal antibodies and positive with the four antipeptide antibodies. Our novel observations provide in vivo evidence of the complexity involved in evaluating HER2 expression, and open a new path for understanding the biologic significance of HER2 status in breast tumors.

Amino Acid Sequence↗

PubMedDate not supplied

Differential denaturation of a crystalline Bence-Jones type cryoprotein as monitored by fluorescence.

1) A Bence-Jones type protein (Cryo-Ver) showing the cold precipitation phenomenon has an extremely low intrinsic fluorescence when excited at 280-295 nm. 2) This fluorescence increases considerably upon denaturation of the molecule by heat or guanidine hydrochloride. Guanidine is about twice as effective as heat in terms of fluorescence yield. 3) The heat-denatured protein is still reactive with anti-cryoVer antibodies, at variance with the guanidine-treated samples. 4) Since the protein contains two tryptophans per mole, one in the constant portion of the molecule, the other in the variable region, it is proposed that heat treatment affects only the variable region, which seems involved in the cryoprecipitation phenomenon.

Bence Jones Protein↗

PubMedDate not supplied

Specificity of rabbit antibodies elicited by related synthetic peptides.

Three 17-residue peptides, presenting from 65% to 70% sequence homology, and one endecapeptide, with no apparent homology with the first three, were chemically synthesized and investigated in their ability to elicit rabbit antipeptide antibodies. The complex cross reactivities of the antisera were investigated by testing the binding of the antibodies to the intact peptides, to their enzymatic fragments, and by the use of specific immunoadsorbents. Antipeptide antibodies may or may not crossreact with related "parent" peptides, this depending upon number, distribution, and localization of amino acid differences in low or high antigenicity regions of the immunogen. Related peptides may elicit antibodies that crossreact almost completely, and therefore not specific for one or the other "parent" peptide. Those antibodies may therefore be of little use for the selective recognition of closely related structures.

Amino Acid Sequence↗

PubMedDate not supplied

Antipeptide antibodies: do they distinguish HLA-alloantigens?

Three immune sera, raised in rabbits against synthetic peptides corresponding in sequence to predetermined regions of the HLA-DQ histocompatibility antigens, were tested for their ability to recognize phenotypically distinct human lymphoblastoid cell lines. The immune sera readily recognize the immunogen. When tested on the cells, they react poorly but seem to exhibit a certain degree of specificity. The possibilities in developing true selective reagents for HLA-alloantigens are considered and discussed.

Alleles↗