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M Z Atassi

Publications and source records attributed to M Z Atassi.

At least 91 records · Page 5Linked to original sources
PubMed1988

T cell response to myoglobin: a comparison of T cell clones in high-responder and low-responder mice.

Mice carrying the H-2b haplotype (e.g., inbred strains C57BL/6 and C57BL/10) are low responders to sperm whale myoglobin when tested in the T cell proliferation assay. Their response is improved by the removal of the Ly-2+ cells from the lymph node population, but it still remains significantly lower than that of cells cells from high-responder strains (e.g., DBA/2, H-2d). To determine whether T cells from the low and high-responder mice recognize the same or different epitopes on the immunizing antigen, we obtained sets of T cell clones from both strains and tested them against peptides representing different regions of the myoglobin molecule, as well as against myoglobins from species other than the sperm whale. Four types of T cell clones were obtained from the DBA/2 mice: 3 types responded to the peptide 107-120 (9 clones altogether), and 1 type responded to the peptide 133-149 (4 clones altogether). The 3 types responding to the peptide 107-120 could be distinguished by their response to horse myoglobin or by the restriction of the response (Ad vs. Ed). Similarly, 5 types of T cell clones were obtained from the C57BL/6 mice: 2 types responded to the peptide 10-22 (1 type, but not the other, responded to horse myoglobin); 1 type responded to the peptide 133-149; and 2 types did not respond to any of the peptides used (1 type, but not the other, responded to dog myoglobin). All 5 types (13 clones altogether) were presumably Ab restricted. These results demonstrate the diversity of epitopes in single antigenic regions and show equivalent heterogeneity of T cell repertoires in high and low responder mice. Attempts to demonstrate specific T cell suppression in the low responder mice failed; only partial, nonspecific suppression was observed.

Animals↗
PubMed1988

Mapping by synthetic peptides of the binding sites for acetylcholine receptor on alpha-bungarotoxin.

A set of seven peptides constituting the various loops and most of the surface areas of alpha-bungarotoxin (BgTX) was synthesized. In appropriate peptides, the cyclical (by a disulfide bond) monomers were prepared. In all cases, the peptides were purified and characterized. The ability of these peptides to bind Torpedo californica acetylcholine receptor (AChR) was studied by radiometric adsorbent titrations. Three regions, represented by peptides 1-16, 26-41, and 45-59, were able to bind 125I-labeled AChR and, conversely, 125I-labeled peptides were bound by AChR. In these regions, residues Ile-1, Val-2, Trp-28, Lys-26 and/or Lys-38, and one or all of the three residues Ala-45, Ala-46, and Thr-47, are essential contact residues in the binding of BgTX to receptor. Other synthetic regions of BgTX showed little or no AChR-binding activity. The specificity of AChR binding to peptides 1-16, 26-41, and 45-59 was confirmed by inhibition with unlabeled BgTX. It is concluded that BgTX has three main AChR-binding regions (loop I with N-terminal extension and loops II and III extended toward the N-terminal by residues 45-47).

Amino Acid Sequence↗
PubMed1988

The regions of alpha-neurotoxin binding on the extracellular part of the alpha-subunit of human acetylcholine receptor.

A set of 18 synthetic uniform overlapping peptides spanning the entire extracellular part (residues 1-210) of the alpha-subunit of human acetylcholine receptor were studied for their binding activity of 125I-labeled alpha-bungarotoxin and cobratoxin. A major toxin-binding region was found to reside within peptide alpha 122-138. In addition, low-binding activities were obtained with peptides alpha 34-49 and alpha 194-210. It is concluded that the region within residues alpha 122-138 constitutes a universal major toxin-binding region for acetylcholine receptor of various species.

Amino Acid Sequence↗
PubMed1988

Cytotoxic T lymphocyte recognition sites on influenza virus hemagglutinin.

When influenza virus infection occurs, part of the cytotoxic T lymphocyte responses induced are directed to the major surface molecule of the virus, the hemagglutinin. However, despite their potential use as a peptide vaccine, little information is available concerning the submolecular areas in the hemagglutinin that are responsible for its immunologic recognition by cytotoxic T lymphocytes. The primary goal of this study is to determine whether submolecular areas recognized by antibodies and helper T cells are also important in the virus-specific, T lymphocyte-mediated cytotoxic responses generated towards virus-infected cells. A panel of synthetic peptides representing areas of the hemagglutinin, homologous to those in influenza AX-31 virus which have previously been shown to bind anti-influenza virus antibodies and provoke proliferation of virus-primed T-helper lymphocytes, was tested in two different cytotoxicity assays. In the experiments presented here, it was found that when selected peptides were incubated with appropriate L929 target cells, lysis by virus-specific cytotoxic T cells was observed. In addition, AX-31-primed lymphocytes preincubated with these synthetic peptides (both individually and as an equimolar mixture) exhibited enhanced lysis of virus-infected syngeneic targets. The cytotoxic responses showed dose-response characteristics in all cases, and in each of the two assays used the same patterns of cytotoxic induction were observed. The recognition of peptides was MHC-restricted since virus-specific cytotoxic T cells from C3H/He mice (H-2k) lysed L929 (H-2k) target cells after incubation with peptides or viruses, but did not lyse P815 (H-2d) targets under the same conditions.

Animals↗
PubMed1988

Conformation-dependent recognition of a protein by T-lymphocytes: apomyoglobin-specific T-cell clone recognizes conformational changes between apomyoglobin and myoglobin.

A T-cell clone specific to apomyoglobin was generated. It was prepared from a T-cell culture obtained by in vitro driving of lymph node cells with apomyoglobin from SJL mice that have been primed in vivo with apomyoglobin. In proliferative assays, the T-cell clone responded to apomyoglobin but did not recognize native myoglobin or any of the synthetic peptides corresponding to the six T sites of myoglobin. The demonstration that a T-cell clone can be isolated, whose specificity is directed entirely to apomyoglobin and not to its counterpart myoglobin, with an identical amino acid composition, indicates the importance of the three-dimensional structure in the presentation of the protein to T cells.

Animals↗
PubMed1988

Molecular recognition of human insulin receptor by autoantibodies in a human serum.

Immune IgG was obtained from a patient's serum with autoantibodies against human insulin receptor (HIR). The binding activity of these autoantibodies to seven synthetic peptides of the alpha-subunit of HIR was examined by radioimmuno-adsorbent titrations. Autoantibodies were bound by two of these peptides, namely alpha 277-299 and alpha 705-731, and this binding was not inhibited by a very large (1,000 x) molar excess of normal human IgG. Furthermore, none of the peptides exhibited any binding activity towards 125I-labelled normal human IgG. Therefore, it was concluded that the regions alpha 277-299 and alpha 705-731 contain autoantigenic sites of HIR. In addition, region alpha 655-670 might constitute a minor antigenic site of HIR. Localization of these autoantigenic sites will permit the molecular investigation of the insulin-like activity of anti-HIR autoantibodies.

Amino Acid Sequence↗
PubMed1987

Profile of the alpha-bungarotoxin-binding regions on the extracellular part of the alpha-chain of Torpedo californica acetylcholine receptor.

The continuous alpha-neurotoxin-binding regions on the extracellular part (residues 1-210) of the alpha-chain of Torpedo californica acetylcholine receptor were localized by reaction of 125I-labelled alpha-bungarotoxin with synthetic overlapping peptides spanning this entire part of the chain. The specificity of the binding was confirmed by inhibition with unlabelled toxin and, for appropriate peptides, with unlabelled anti-(acetylcholine receptor) antibodies. Five toxin-binding regions were localized within residues 1-10, 32-41, 100-115, 122-150 and 182-198. The third, fourth and fifth (and to a lesser extent the first and second) toxin-binding regions overlapped with regions recognized by anti-(acetylcholine receptor) antibodies. The five toxin-binding regions may be distinct sites or, alternatively, different 'faces' in one (or more) sites.

Amino Acid Sequence↗
PubMed1987

Non-specific peptide size effects in the recognition by site-specific T-cell clones. Demonstration with a T site of myoglobin.

Six regions (T sites) of myoglobin (Mb) were found by a comprehensive synthetic strategy to stimulate Mb-primed lymph-node cells. To define precisely the N-terminal boundary of the immunodominant T site (residues 107-120) with site-specific T-cell clones and to determine the effects of peptide size on their stimulation, two sets of peptides were employed. In one set, the peptides were elongated to the left from His-113 by one-residue increments of the Mb sequence. The other set represented an identical stepwise elongation by one-residue increments of the Mb sequence, but which were extended by additional unrelated ('nonsense') residues to a uniform size of 14 residues. Examination of the proliferative responses of eight T-cell clones, derived from Mb-primed DBA/2 (H-2d) or SJL (H-2s) mice, revealed a dramatic non-specific size requirement. In every clone, the longer nonsense-extended peptides achieved maximum stimulating activity at a lower optimum peptide dose than its natural-sequence, but shorter, analogue. In addition, slight (one-residue) differences in the N-terminal boundaries among the clones was observed. Thus, the fine specificity of each clone was mapped to the region from residue 111 or 112 to about residue 120 of Mb, which coincides with the site of B-cell recognition and resides in a small discrete surface region of the protein chain.

Animals↗
PubMed1987

Immune recognition of human major histocompatibility antigens: localization by a comprehensive synthetic strategy of the continuous antigenic sites in the first domain of HLA-DR2 beta chain.

A comprehensive synthetic approach, previously developed in this laboratory, has been applied to screen the entire first domain (residues 1-95) of the HLA-DR2 beta chain for the full profile of continuous regions that are recognized by human allo-antisera and anti-DR or anti-beta chain antisera raised in other species. Nine consecutive peptides, that were 15 residues each and overlapped by 5 residues, covering the first domain of the DR2 beta chain were synthesized, purified and characterized. The antibody-binding activities of the peptides were determined by radioimmunosorbent titrations. This established the full profile of peptides having specific antibody-binding activity with these various antisera. Three continuous antigenic sites were localized in this domain by all of antisera tested. Peptide 81-95 appeared to be the most immunodominant (i.e. bound the highest amounts of antibodies) in most antisera tested. Although their immunodominance varied with the antisera and boundary shifts were present, the submolecular regions recognized on the first domain of DR2 beta appeared to be similar with antisera against the DR2 (alpha beta I) complex or against the isolated beta chain. Furthermore, recognition was independent of the host species from which the antisera were obtained.

Animals↗
PubMed1987

The continuous antigenic regions in the second domain of the beta chain of human MHC DR2 antigen: antigenic profile of the entire extracellular part of the chain.

Ten consecutive 15-residue peptides (except for peptide 181-198) that spanned the entire second domain of the HLA DR2 beta chain and overlapped by 5 residues were synthesized, purified and characterized. The antibody-binding activities of the peptides with human alloantisera and with antisera raised in other species were determined by radioimmunosorbent titrations. This established the full profile of peptides having specific antibody-binding activity with these various antisera. The continuous antigenic sites in this domain were localized within four regions. The localization of the antigenic regions on the second domain completes the description of the antigenic profile of the entire extracellular part of the beta chain of HLA DR2. Thus, the continuous antigenic sites on the extracellular part of the DR2 beta subunit reside within seven regions with an eighth site being recognized somewhat weakly with some antisera. As was found for the first domain, the immunodominance of a given site varied with the antisera and boundary shifts were present. The submolecular regions recognized on the second domain of the DR2 beta were independent of the host species from which the antisera were obtained.

Amino Acid Sequence↗
PubMed1987

T lymphocyte recognition of acetylcholine receptor: localization of the full T cell recognition profile on the extracellular part of the alpha chain of Torpedo californica acetylcholine receptor.

A series of eighteen consecutive overlapping synthetic peptides, of uniform size and overlaps, which encompass the entire extracellular part (residues 1-210) of the Torpedo californica acetylcholine receptor alpha chain were examined in vitro for their ability to stimulate lymph node cells from acetylcholine receptor-primed C57BL/6 (H-2b), C3H/He (H-2k), SWR (H-2q) and SJL (H-2s) mice. The recognition sites (T sites) by acetylcholine receptor-primed lymph node cells from these mouse strains resided within six regions on the extracellular part of the alpha chain. Three of the regions recognized by T cells coincided with regions recognized by antibodies (i.e. B cells) and one of these three regions also coincided with an alpha-neurotoxin-binding region. It is noteworthy that, in addition to sites recognized by both T and B cells, the protein has at least two sites which are recognized exclusively by T cells and to which no detectable antibody responses are directed.

Animals↗
PubMed1987

T-cell recognition and antigen presentation of myoglobin.

Determination of the T-cell recognition profile of Mb by the overlapping peptide strategy revealed that the protein has six T sites. Five of these coincide with the antigenic sites while one site was recognized exclusively by T cells and not by any detectable levels of antibody. Recognition of the synthetic T sites by protein-primed T cell lines or clones indicated that T cells display an unusual peptide size requirement beyond the essential contact residues of the T site. The antigen presentation of Mb has been examined with the significant advantage of knowing the full profiles of T- and B-cell recognition of this multi-determinant antigen. Significant differences in the patterns of T-cell recognition were observed following protein-priming as compared to peptide-priming. The absence of a clear relationship between these patterns of recognition presents a strong evidence against a mechanism of antigen presentation which is dependent on the generation of peptide fragments with the latter being the 'presented' species. From this new perspective, the protein molecule must be predominantly presented in its intact form.

Animals↗
PubMed1987

T-cell recognition and antigen presentation of lysozyme.

Several years ago, this laboratory introduced a comprehensive strategy for the systematic localization of all the continuous sites on a protein that are involved in B- and T-cell recognition. The strategy depends on the synthesis of consecutive overlapping peptides that together account for the entire protein chain. Using this approach, the full submolecular profile of continuous regions on hen egg lysozyme recognized by T cells (T sites) were localized. Four major T-cell recognition sites, three of which were subject to individual genetic control, were localized in the six mouse strains examined. In addition to these four continuous T sites, T-cell recognition of lysozyme also involved the three previously defined discontinuous antibody binding sites as demonstrated with lysozyme-specific long-term T cell cultures. Contrary to a long held impression, T-cell recognition, therefore, is not restricted only to sequence features, but can also be directed to protein discontinuous surface areas of high conformational dependency. More recently, we have examined in two mouse strains the proliferative response to peptides and to native protein of lymph node cells from mice primed with synthetic overlapping peptides either individually or as a mixture. It was found that the pattern of T-cell recognition observed after priming with peptides differs from that obtained when the native protein is used as the immunogen. If antigen processing proceeds via fragmentation, then only those regions containing T sites would be expected to be effective in priming for a T-cell response to the intact protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The regions of T-cell recognition on the extracellular part of the alpha chain of Torpedo californica acetylcholine receptor.

A comprehensive synthetic approach was employed to identify the continuous regions of T-cell recognition on the alpha-chain of Torpedo californica acetylcholine receptor (AChR). Eighteen synthetic consecutive overlapping peptides, of uniform size and overlaps, that spanned the entire extracellular part (residues 1-210) of the alpha chain were examined for their in vitro stimulation of lymph node cells from AChR-primed C57BL/6 (H-2b), C3H/He (H-2k), SWR(H-2q) and SJL (H-2s) mice. The T-cell recognition sites (T sites) in the AChR-primed mouse strains resided within six regions on the extracellular part of the alpha-chain. Three of the regions recognized by T cells coincided with regions recognized by antibodies (i.e. B cells) and one of these three regions also coincided with an alpha-neurotoxin binding region. It is noteworthy that, in addition to sites recognized by both T and B cells, the protein has at least two sites which are recognized exclusively by T cells and to which no detectable antibody responses are directed.

Animals↗
PubMed1987

Profile of the continuous antigenic regions on the extracellular part of the alpha chain of an acetylcholine receptor.

Reaction of overlapping synthetic peptides spanning the extracellular part (residues 1-210) of the alpha chain of the Torpedo californica acetylcholine receptor (an alpha 2 beta gamma delta pentamer) with anti-receptor antibodies produced the profiles of the continuous antigenic regions of the correlate segment. Essentially similar profiles were recognized by rabbit and outbred mouse antibodies against isolated receptor or mouse antibodies against membrane-bound receptor. The antigenic sites reside within eight continuous regions: residues 1-14, 25-36, 41-53, 63-75, 102-114, 128-138, 172-182, and 188-198. Five of these regions (the second and the fifth through the eighth) appeared to be immunodominant. Significantly, two of these antigenic regions (i.e., those residing within residues 128-138 and 188-198) coincided with known toxin-binding regions. The antigenic profile suggests that recognition is directed to the intact molecule and only very slightly to the processed (fragmented) protein.

Animals↗
PubMed1987

Antigenic regions on the beta chain of human chorionic gonadotropin and development of hormone specific antibodies.

Five peptides corresponding to four regions of the beta chain of human chorionic gonadotropin (hCG), were synthesized, purified and characterized. The four regions studied were selected on the basis of sequence differences between the beta chain of hCG (beta hCG) and the beta chains of related hormones. The peptides were found to bind rabbit and mouse anti-hCG antibodies as well as rabbit anti-beta chain antibodies, but did not bind antibodies against the alpha chain or against other hormones. All the peptides, even in their free form, were able to elicit high titer antisera in both rabbits and mice. In all cases, anti-peptide antisera bound to the immunizing peptide as well as to the native hCG and the isolated beta chain. These anti-peptide antisera did not bind to unrelated peptides, the alpha chain of hCG or to other hormones with very similar beta chains such as human luteotropic hormone (hLH), ovine luteotropic hormone (oLH) and equine chorionic gonadotropin (eCG). Since the areas represented by these peptides elicit antibodies that are specific for human beta hCG, they can formulate the basis for the development of discriminatory reagents for the beta chain of hCG.

Antibody Specificity↗
PubMed1987

Localization of the functional sites on the alpha chain of acetylcholine receptor.

A comprehensive synthetic approach, previously developed in this laboratory, has been applied to systematically screen the entire extracellular part (residues 1-210) of the alpha chain of the Torpedo californica acetylcholine receptor (AChR) for the profiles of the continuous regions that are recognized by antibodies against free, or membrane-sequestered, AChR; the regions recognized by AChR-primed T cells; the regions that bind alpha-bungarotoxin and cobratoxin; and an acetylcholine-binding region. Eight continuous antigenic sites were localized in this part of the alpha chain by all of the antisera tested. The sites were independent of the host species from which the antisera were obtained and were also similar to antisera against the isolated pentameric AChR or against the membrane-sequestered AChR. Six regions were found to stimulate AChR-primed T cells (T sites). Three of the T sites coincided with regions recognized by antibodies. At least two T sites had no detectable antibody responses directed to them. Five toxin-binding regions were localized, and may constitute distinct sites or, alternatively, different faces in one (or more) sites. Some of these regions coincided with regions recognized by anti-AChR antibodies. One of the toxin-binding regions bound acetylcholine, and immunization with this peptide induced experimental autoimmune myasthenia gravis.

Acetylcholine↗