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A Leprini

Publications and source records attributed to A Leprini.

At least 37 records · Page 2Linked to original sources
PubMed1992

The inclusion of the type III repeat ED-B in the fibronectin molecule generates conformational modifications that unmask a cryptic sequence.

We have previously reported an anti-fibronectin monoclonal antibody (mAb) (BC-1) which reacts with an ED-B-containing beta-galactosidase-fibronectin fusion protein but not with an identical beta-galactosidase-fibronectin fusion protein in which the ED-B sequence is omitted. In further experiments aimed at localizing more precisely the epitope recognized by this mAb, we demonstrate that 1) the mAb BC-1 is indeed specific for ED-B-containing fibronectin (FN) molecules even though the epitope recognized by this mAb is localized on the type III homology repeat 7 (the one which precedes the ED-B sequence) and 2) in fibronectin molecules lacking the ED-B sequence, this epitope is masked. We further demonstrate that, to mask the epitope recognized by the mAb BC-1, the presence of at least half of the FN type III homology repeat 9 is necessary. We also report the production of the mAb IST-6 which recognizes only FN molecules in which the ED-B sequence is lacking. These data clearly demonstrate that the presence of the ED-B sequence within FN molecules generates conformational modification in the central part of the molecules that unmasks previously cryptic sequences and masks others.

Amino Acid Sequence↗
PubMed1991

Human tenascin: primary structure, pre-mRNA splicing patterns and localization of the epitopes recognized by two monoclonal antibodies.

By sequencing cDNA clones which cover the complete coding region of human tenascin (TN), we have established its primary structure. This confirms that, as in the case of chicken, TN is mainly made up of three groups of sequences with a high homology to Epidermal Growth Factor (EGF) fibronectin (FN) type III repeat and fibrinogen. Furthermore, we have determined the amino-terminal sequence of the mature peptide directly on purified TN. The main differences with respect to the chicken TN molecule are that in the human there are 14 and half EGF-like repeats compared to 13 and half in the chicken and that, as previously reported, there are 15 FN-like repeats compared to 11 in the chicken. By Polymerase Chain Reaction (PCR) amplification we have also studied the different splicing patterns of the TN pre-mRNA in cultured cells. The results show the presence of at least four different isoforms containing different numbers of FN-like type III repeats. Using purified human TN as immunogen, we have obtained numerous monoclonal antibodies (Mabs) to TN. By screening a human melanoma cDNA library in the expression vector lambda gt11 with these Mabs and subsequently sequencing the insert of the positive clones, we have been able to localize, within the TN molecule, the epitopes recognized by two of these Mabs: BC-4, which recognizes an epitope within the EGF-like sequence and BC-2 which recognizes an epitope within the FN like type III repeats whose expression is regulated by alternative splicing of the TN pre-mRNA. Thus, while the Mab BC-4 may be useful in studies on TN distribution (since it recognizes all different TN isoforms) BC-2 may be useful in the study of the expression of particular TN isoforms generated by the alternative splicing of the TN primary transcript.

Amino Acid Sequence↗
PubMed1991

Procedure for the purification of the fibronectin proteolytic fragments containing the ED-B oncofetal domain.

Fibronectin (FN) is the blend of structurally different molecules (isoforms) whose makeup varies depending on the FN sources. Fibronectin polymorphism is caused by three sequences (called ED-A, ED-B, and IIICS) which may be included or excluded from the FN molecule depending on the alternative splicing patterns of a single primary transcript. The sequence ED-B, which is a complete type III repeat of 91 amino acids, presents some interesting peculiarities: it is the most conserved FN region and, in normal adult tissues, the ED-B-containing FN has an extremely restricted distribution while having a much greater expression in fetal and tumor tissues (Carnemolla et al., 1989, J. Cell Biol. 108, 1139-1148), suggesting that the ED-B sequence may confer to the FN molecules specific biological activities required during ontogenesis and oncogenetic processes. Here we describe a detailed procedure to purify fibronectin fragments containing the ED-B sequence. These purified fragments are useful reagents in the study of the biological function(s) of the ED-B-containing FN molecules.

Amino Acid Sequence↗
PubMed1991

Autoreactive lymphocytotoxic IgM antibodies in highly sensitized dialysis patients waiting for a kidney transplant: identification and clinical relevance.

The contribution of different families of lymphocytotoxic antibodies in the serologic reactivity of 45 highly sensitized dialysis patients (HSDP) (panel reactivity antibody value-PRA greater than 80%) was assessed by analyzing patients' sera for the presence of auto- and alloreactive IgM and alloreactive IgG antibodies. A total of 220 sera was screened at different incubation temperatures, before and after treatment with the reducing agent dithiothreitol, against a large variety of cell targets by means of complement dependent cytotoxicity (CDC) and antiglobulin augmented (AHG) CDC assays. The results allowed to subdivide the HSDP under study into four groups: Group 1 consisted of 13 untransplanted patients and 14 patients with a prior failed graft whose PRA values did not change following DTT treatment. Alloreactive IgG antibodies alone, with anti-HLA specificity, were present in the sera of this patient group. Group 2 consisted of 3 untransplanted patients whose sera did not contain any autolymphocytotoxic antibody but appeared completely unreactive to panel lymphocytes following DTT treatment, thus confirming the presence of alloreactive IgM only endowed with antiHLA reactivity. Group 3 consisted of 4 untransplanted and 4 patients with a prior failed graft whose sera were found to contain in addition to autoreactive IgM also alloreactive IgG antibodies. Their PRA values declined after DTT treatment on average from 96.2% to 45% and from 95% to 52.5%, respectively. Group 4 consisted of 6 untransplanted patients whose PRA reactivity to both autologous and panel lymphocytes completely disappeared following DTT treatment, thus indicating that their sera contained exclusively autolymphocytotoxic IgM antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Transforming growth factor-beta regulates the splicing pattern of fibronectin messenger RNA precursor.

Fibronectin (FN) polymorphism is caused by alternative splicing patterns in at least three regions (ED-A, ED-B and IIICS) of the primary transcript of a single gene. Using monoclonal antibodies, we previously demonstrated that transforming growth factor-beta (TGF-beta) preferentially increases the accumulation of the FN isoforms containing the ED-A sequence in cultured normal human fibroblasts [Balza et al., (1988) FEBS Lett. 228, 42-44]. To determine the basis of this effect, we have examined through S1 nuclease analysis, the levels of ED-A- and ED-B-containing mRNAs in cultured normal human skin fibroblasts before and after TGF-beta treatment. These experiments have shown that TGF-beta increases the relative amount of m-RNA for ED-A- and ED-B-containing FN isoforms. These data demonstrate that a growth factor may regulate the splicing pattern of a pre-mRNA.

Cell Line↗
PubMed1990

[Hematic infiltrates and the expression of HLA-DR antigens in naso-sinusoidal polyps of the fibrous type].

In this study fibrous nasal polyps, obtained from four patients, were analyzed by means of immunocytochemical methods for the presence of interstitial hematic cell infiltrate and HLA-DR molecule expression. This histologic type accounted for 36.4% of nasal polyps studied. Our results demonstrated that cells belonging to monocyte-macrophage lineage were mainly detected within fibrous and edematous zones (greater than 50%), whereas T cells were found within the subepithelial peripheral connective tissue (greater than 60%). Surface and gland epithelial cells appeared to be more intensely stained for HLA-DR molecules than nasal epithelium of normal subjects, thus indicating that the intensity of HLA-DR molecule expression correlated with the presence of a hematic cell infiltrate. Nasal polyps are a frequent pathology whose etiology has not yet been completely clarified. The present study provides additional information about the fibrous polyp structure and can support some speculations on the nasal polyp etiology.

Blood Cells↗
PubMed1990

[Pancreatic passenger leukocytes in organs obtained from cadaver donors for allotransplantation].

In previous studies we have demonstrated that human normal pancreata were populated by interstitial mononuclear cells constituted by dendritic cells (70%), macrophages (30%) and few B cells (less than 1%). Furthermore, the endocrine parenchyma and the centroacinar cells appeared negative for the detection of HLA-A,B,C molecules. In the present report, 15 pancreata from cadaver donors were studied by means of immunohistochemical methods. 5 out of 15 organs were found to contain a larger amount of interstitial hematic cells that were constituted mainly by macrophages and B cells, together with a small percentage of granulocytes and T cells. In such "infiltrated" pancreata both endocrine parenchyma and centroacinar cells displayed a positivity for HLA-A,B,C antigens. As HLA-class I antigens have importance in allo-recognition and rejection responses, our data suggest that pre-transplant biopsies may be useful for a better evaluation of the pancreatic tissue immunogenicity.

Cadaver↗
PubMed1990

[Anti-HLA antibodies (Ab1) and anti-idiotypic antibodies (Ab2) directed against Anti-HLA Ab1 in various preparations of polyspecific immunoglobulins for intravenous use].

In this study, different intravenous immunoglobulin infusions (I.V. Ig.), were analyzed for the presence of either anti-HLA antibodies (Ab1) or anti-idiotypic antibodies (Ab2) directed against Ab1 anti-HLA. No evidence of either antibody types was found in tested I.V. Ig. preparations. Because of the absence of Ab1 anti-HLA, prophylactic and/or therapeutic use of I.V. Ig. appears safe in patients waiting for organ graft or in transplanted patients. The lack of Ab2 anti-Ab1 anti-HLA makes worthless the utilization of such preparations for neutralization of Ab1 present in highly sensitized dialysis patients or suppression of their production in transplanted patients in contrast with the previous reports suggesting this possibility.

Antibodies, Anti-Idiotypic↗
PubMed1989

[The Leu 7+ cell population of the human pancreas: preferential distribution and morphology].

Anti-Leu 7 is a monoclonal antibody which recognizes an antigenic determinant present on the surface of a subset of human large granular lymphocytes and on central and peripheral neural elements. Furthermore it cross-reacts with an intracellular protein of secretory granule matrix in neuroendocrine cells. The presence of Leu 7+ cells has been studied in lymphoid and non-hemopoietic organs. We have analyzed the Leu 7 positivity in six pancreata from cadaver donors by means of immunocytochemical methods. Leu 7+ cells were found to be also present in the exocrine portion of the organ in which they represent a nonhomogeneous cellular population. In fact, two different types of Leu 7+ elements populate the exocrine pancreas: a, Leu 7+ cells showing an intracellular granule positivity; b, Leu 7+ cells showing surface positivity. The endocrine pancreas, in contrast, contains the majority (85%) of Leu 7+ elements, belonging to the intracellular positive type only.

Antibodies, Monoclonal↗
PubMed1989

[Modulation of the expression of histocompatibility antigens class I (HLA-A,B,C) in the human pancreas].

In this study the expression of HLA class I molecules was analysed on caudal portions of ten pancreata from cadaver donors by means of indirect immunoperoxidase and immunophosphatase techniques. In 7 out of ten pancreata the results showed that islets tissue was almost negative for the expression of HLA Class I antigens as opposed to exocrine tissue that appeared positive. Within exocrine tissue and large sized islets strongly positive interstitial cells were also detected. Double stainings showed that the strongly positive interstitial cells expressed also Leu M1 antigens. Preliminary studies on the remaining three pancreata demonstrate an increase of hematic interstitial cells together with a parallel increase of HLA class I antigens by endocrine parenchyma. The above data suggest that an increase of interstitial cells within pancreas may influence islets antigenicity.

Antigens, Differentiation, Myelomonocytic↗
PubMed1989

[Characterization with dithiothreitol (DTT) of IgM auto-lymphocytotoxic antibodies in dialyzed patients awaiting kidney transplants].

A group of 42 sensitized dialysis patients showing high reactivity (81%-100%) against a random panel of peripheral blood lymphocytes (PBL), were analyzed for the presence of autoreactive lymphocytotoxic antibodies. The test was performed at different temperatures (4 degrees C, 22 degrees C, 37 degrees C) with dithiothreitol (DTT) against autologous PBL, EBV-induced autologous B lymphoblasts (A-BCL), K562 cells and T lymphocytes. Thirteen of 42 patients had IgM auto-lymphocytotoxic antibodies. The broadly reactive IgM autoantibodies could be inactivated by treatment with DTT 5 mM and allowed the identification of the presence of autoantibodies alone or in combination with anti-IgG alloantibodies.

Autoantibodies↗
PubMed1987

Morphology, cytochemical features, and membrane phenotype of HLA-DR+ interstitial cells in the human pancreas.

The morphology, histological distribution, surface, and enzymatic phenotype of pancreatic HLA-DR+ cells were studied on seven human pancreata, removed from cadaver donors. Frozen and paraffin-embedded pancreas sections were stained with a battery of monoclonal antibodies by indirect immunofluorescence, immunoperoxidase, and immunophosphatase techniques. Two type of cells were found to express HLA-DR surface molecules: endothelial cells and nonfibroblastic non-B and non-T interstitial elements. The latter cells, which were localized both in the exocrine and endocrine portions of the organ, were distinguished in two main families (macrophagic and dendritic) according to their morphology, surface phenotype, and lysosomal enzymatic activities. The phenotype of cells belonging to macrophagic cell family was the following: Leu M1+, Leu M2+, Leu M3+, OKM1+, and OKT6-. In addition these cells were positive for the expression of lysosomal enzymes such as alpha-naphthyl acetate esterase (ANAE) and acid phosphatase (AP). The "dendritic" cell family comprised, among others, cells that were characterized by the presence of numerous finger-like projections, the absence of Leu M1, Leu M2, Leu M3, OKM1, OKT6 surface antigens, and by the negativity for ANAE and AP. These "dendritic looking cells" (DLC) constituted the most represented DR+ cell type within pancreatic islets. The demonstration of dendritic cells within human islets may justify, in humans also, in vitro procedures of intra-islet dendritic cell removal prior to transplantation, in the attempt of islet rejection prevention.

Dendritic Cells↗