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Biomedical subjects

F Celada

Publications and source records attributed to F Celada.

At least 37 records · Page 2Linked to original sources
PubMed1988

Differential activation of T cell clones stimulated by macrophages exposed to antigen complexed with monoclonal antibodies. A possible influence of paratope specificity on the mode of antigen processing.

We have used the enhanced uptake by FcR-bearing cells observed when Ag is administered as an immune complex to investigate the possible impact of specific antibodies on processing and presentation of antigen by accessory cells. The Ag Escherichia coli beta-galactosidase alone or bound to different mAb was incubated with peritoneal macrophages. These were subsequently exposed to a battery of Ag-specific T hybridoma clones. The resulting production of IL-2 was taken as a measure of effective presentation. The results of 43 mAb-T clone combinations showed a potentiation of presentation of Ag at substimulatory concentration in the majority of the cases, indicating that each mAb is conducive to FcR-mediated uptake by macrophages, and that each T clone can be stimulated by properly presented Ag. In contrast, nine combinations yielded a lower response, two of them falling to baseline values. We attribute these results, which corroborate our previous evidence of directional help in the beta-galactosidase system, to a modulation in enzymatic processing of Ag and its subsequent presentation imposed by the paratope of the mAb binding to the relevant epitope.

Antibodies, Monoclonal↗
PubMed1988

Detection of parasite related antigens associated with conglutinin binding immune complexes in patients with Schistosoma haematobium.

An ELISA assay was designed to detect the presence of parasite related antigens associated with circulating immune complexes in patients affected by urinary schistosomiasis. The assay makes use of bovine conglutinin as the immune complex recognition unit and of human anti-Schistosoma antibody as the antigen recognition unit. Using this method we showed that 10 of 15 (67%) patients with a positive polyethylene glycol assay had circulating immune complexes in which parasite antigens could be detected.

Antigen-Antibody Complex↗
PubMed1988

Preferential pairing of T-B specificities in the same antigen: the concept of directional help.

It is important for an effective planning of the new generation of vaccines to consider that the eventual response is regulated by the interplay of stimulating and suppressing epitopes, resulting in dominance of certain sites over others, and that in order for a molecule to be crossimmunogenic with the outside invader both B and T epitopes must be present. However, T-B cooperation is not random but is guided by preferential pairing of sites within a single macromolecule; this situation can be explained by antigen processing by B cells and paratope mediated interference with endosomial degradation.

Antibodies↗
PubMed1988

Effect of cyclosporine on the antigen-presenting function of human and murine accessory cells.

Recent reports have challenged the belief that accessory cells are resistant to cyclosporine. Such a tenet was based on the observation that several functions of accessory cells, such as IL-1 production and phagocytosis, are resistant to the drug. On the other hand, when a less primitive, more refined function of accessory cells was examined--i.e., the capacity to take up, process, and present antigen in an MHC-restricted fashion to antigen-specific T lymphocytes, CsA proved to be an effective inhibitor. In contrast to this finding, when antigen was provided in the form of an immune complex prepared with a monoclonal antibody, uptake of antigen--likely mediated by the Fc receptors--and subsequent processing and presentation were not affected by CsA. These results suggest that, depending on whether the antigen is taken up by constitutive or by receptor-mediated endocytosis, accessory cells can be functionally defined as resistant or sensitive to CsA.

Animals↗
PubMed1987

Methods for the selection and growth of antigen-specific cytolytic T lines and clones bearing a defined T cell receptor beta chain marker.

Murine cytolytic T lymphocyte (CTL) clones specific for type A influenza virus antigens were generated by in vitro stimulation with syngeneic virus-infected cells in the presence of T cell growth factor (TCGF). All CTL clones recognize viral determinants shared by PR8 and X31 influenza viruses in association with a class I antigen, coded either by the H-2K or H-2D end of the appropriate haplotype. All clones express the Lyt2 antigen marker. Two of five clones also express an antigenic determinant of the V beta chain of the T cell receptor (TCR) identified by F23.1 monoclonal antibody. To effectively generate F23.1+ and antigen-specific CTL clones, heterogenous CTL lines were expanded with F23.1 coated Sepharose beads in the presence of TCGF and then stimulated with PR8 virus-infected cells. Thus, both the proliferative activity to PR8 and the expression of the F23.1 marker was increased significantly. Alternatively, F23.1+ T cells were sorted from in vivo primed mice and expanded with PR8 virus-infected stimulator cells in the presence of TCFG. This F23.1+ T cell line exhibited antigen-specific cytotoxicity for PR8 virus-infected target cells. Additionally, in an 'FcR-focused killing' assay only the F23.1+ CTL line and F23.1+ clones lysed Fc receptor bearing target cells in the presence of F23.1 antibody. These findings indicate that antigen-specific and F23.1+ clones can be selected with high efficiency by alternating stimulation with influenza virus-infected cells and with F23.1-coated Sepharose beads or through the use of a cytofluorograph. The usefulness of antigen-specific and F23.1+ CTL clones and other possible strategies for their selection are discussed.

Animals↗
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↗
PubMed1987

Identification of autoreactive lymphocytotoxic antibodies in sensitised dialysis and kidney transplant patients.

Autoreactive lymphocytotoxic antibodies, which have been found in sensitised dialysis patients, are generally not considered to be harmful to a renal allograft. In this work the presence of such autoreactive antibodies was investigated in the following groups of sensitised endstage renal disease patients: (a) dialysis patients waiting for a first kidney transplant, (b) kidney transplanted patients, and (c) dialysis patients with a previous failed graft. Only sera from the above patients which showed high reactivity (greater than 30%) against peripheral blood lymphocytes of a random cell panel (R-PBL), were screened for the presence of autoreactive lymphocytotoxic antibodies, by testing at different temperatures against autologous T lymphoblasts (PHA-ATL) and EBV-induced autologous B lymphoblasts (EBV-ABL). The results showed that both blood transfusions, and viral infections such as cytomegalovirus (CMV), correlated with the presence of autoreactive antibodies, and that in addition, by using PHA-ATL and/or EBV-ABL as absorbing reagents, it was possible to remove the antibodies. These absorption procedures allowed the identification of the presence of autoreactive antibodies alone or in combination with other alloantibodies.

Adolescent↗
PubMed1986

Difference in sensitivity to cyclosporine in vitro of human alloreactive lines and clones.

The effectiveness of cyclosporine (CsA) as immunosuppressive agent in human kidney graft rejection is well established. However, in spite of efforts to maintain optimal plasma levels, a fraction of transplanted patients undergo rejection episodes and/or irreversible chronic rejection. This suggests that immunosuppression by CsA cannot control the alloreactive response if there is a high degree of histoincompatibility for HLA or non-HLA antigens, or it has little effect on the "high responder" patient. Both possibilities are difficult to test in the human system. A third hypothesis, the existence of individual CsA resistance, was tested by evaluating the in vitro inhibitory activity of CsA on alloreactive T cell lines from several individuals. A different degree of in vitro sensitivity to the drug was observed among alloreactive lines generated from different individuals and among clones obtained from the same bulk line. The variability at the individual level and at the clonal level may account for the onset of CsA-resistant rejection assuming that in vivo a positive selection in the presence of the drug occurs and allows for the resistant clones, if present, to dominate the sensitive ones.

Cell Line↗
PubMed1985

The serum capacity to solubilize immune complexes (ICSC) measured by an enzyme-anti-enzyme complex probe.

The capacity to solubilize immune complexes can be readily measured by incubating the test serum with a suspension of an immune precipitate formed by beta-galactosidase and anti-beta-galactosidase antibody, and then reading the enzyme units (EU) liberated in the clear supernatant. Our method is rapid and inexpensive; it can be performed in plates and read in scanning colorimeters. Although on large numbers of observations the ICSC is significantly correlated with the CH50, a few discordant cases suggest that solubilization and haemolysis are functions of the alternative and classical pathways of complement respectively.

Antigen-Antibody Complex↗
PubMed1985

Constraints in T-B cooperation related to epitope topology on E. coli beta-galactosidase. I. The fine specificity of T cells dictates the fine specificity of antibodies directed to conformation-dependent determinants.

Experiments to test the relationship between the epitopes on a protein antigen recognized by T and B cells in their collaboration to produce antibody cannot rely solely on hapten-carrier models. In the present work we used E. coli beta-galactosidase, a molecule whose tertiary and quaternary epitopes have been well characterized, as the model antigen. T helper cells were raised by stimulating mice with the intact or the denatured molecule or with any of several beta-galactosidase cyanogen bromide peptides. In a series of in vitro helper T cell assays we confronted the various T populations with B cells preimmunized with the native antigen, and we tested their capacity to help production of (a) binding antibodies and (b) antibodies directed to single conformational epitopes, characterized by their capacity to protect the enzyme from heat denaturation or to activate defective beta-galactosidase. According to our results, (a) equivalent T cell help can be provided by T helper cells primed with native or denatured antigen, even for the production of "conformational" antibodies; (b) one of the peptides (CB-18) is most efficient in raising help for binding antibodies; and (c) two peptides (CB-20 and CB-21) rank highest in priming T helper cells for the eventual production of protecting and activating antibodies, respectively. Thus, not every beta-galactosidase-specific T helper cell is useful in providing help to B cells specific for any particular epitope on the molecule, but rather preferential pairings exist, possibly governed by a proximity rule.

Animals↗
PubMed1985

Inhibition of the accessory function of murine macrophages in vitro by cyclosporine.

The accessory function of macrophages, which is strictly related to the induction of T cell activation, has been studied to determine whether it is affected by cyclosporine (CsA). Irradiated spleen cells, used as a source of macrophages, were pulsed overnight with beta-galactosidase (GZ) in the presence of CsA. After washing of the pulsed macrophages, cells from a GZ-specific T cell line were added to cultures and 3H-thymidine incorporation was measured 72 hr later. We found that 500 ng/ml CsA present during macrophage pulsing with GZ reduced T cell proliferation to 5%. On the other hand, 100 ng/ml CsA almost completely abrogated the proliferative response when present for the duration of the culture. Similar results were also obtained using antigen-pulsed peritoneal-adherent macrophages to stimulate the T cell line to proliferate, or a T hybridoma clone to produce interleukin-2 (IL-2). The possibility that CsA actually affects interleukin-1 (IL-1) production by macrophages by inhibiting uninvolved T cells could be ruled out. We conclude that CsA-induced inhibition of T cell functions (proliferation and IL-2 production) is partially due to the effect of the drug on the accessory function of macrophages. This immunosuppressive mechanism of action of CsA on macrophages has not been previously described.

Animals↗
PubMed1984

Follow-up of circulating immune complexes in the course of acute viral hepatitis, and correlation with serologically relevant parameters.

Type A, type B and type non-A, non-B hepatitis patients were followed up. Several parameters were checked at ten day intervals. Circulating immune complexes (CIC) were detected in a large percentage of patients by using the PEG test and an assay that makes use of bovine conglutinin (K) as recognition unit, and an enzymatically labelled immune complex as the probe. The decrease in the mean level of CIC in the patients correlated with the decrease in serum transaminases and bilirubinaemia in type A and type B hepatitis. Although the pattern of the mean values of the two assays was similar for type A and type B hepatitis, when the two CIC assays were compared for each patient, no significant correlation was found. In light of these and previous results, the necessity for performing CIC monitoring with more than one assay is also discussed.

Acute Disease↗