Search PubMed⌕ Search

Biomedical subjects

A Vitiello

Publications and source records attributed to A Vitiello.

At least 37 records · Page 2Linked to original sources
PubMed1991

Analysis of the HLA-restricted influenza-specific cytotoxic T lymphocyte response in transgenic mice carrying a chimeric human-mouse class I major histocompatibility complex.

Transgenic murine lines have been constructed that express a chimeric class I molecule composed of the alpha 1 and alpha 2 domains of HLA-A2.1 and the alpha 3, transmembrane, and cytoplasmic domains of H-2Kb. Upon immunization with influenza virus, transgenic mice developed a strong A2.1Kb-restricted cytotoxic T lymphocyte (CTL) response specific for the same matrix protein epitope that serves as the dominant A2.1-restricted determinant in the equivalent human response. Fine specificity analysis of CTL clones using truncated peptides revealed strong similarity between the response repertoire of transgenic mice and that previously reported using influenza-specific A2.1-restricted CTL clones from humans. This suggests that even when considering T cell responses by different species, the alpha 1 and alpha 2 domains of the restriction element play a dominant role in determining the CTL specific repertoire. Thus, substituting the alpha 3 domain of A2.1 with a murine counterpart has permitted development of a transgenic strain that should serve as an excellent model system in studies of HLA-restricted responses.

Animals↗
PubMed1990

The role of beta 2-microglobulin in peptide binding by class I molecules.

Efficient transport of class I major histocompatibility complex molecules to the cell surface requires association of the class I heavy chain with endogenous peptide and the class I light chain, beta 2-microglobulin (beta 2M). A mutant cell line deficient in beta 2M transports low amounts of nonpeptide-associated heavy chains to the cell surface that can associate with exogenously provided beta 2M and synthetic peptide antigens. Normal beta 2M-sufficient cells grown in serum-free media devoid of beta 2M also require an exogenous source of beta 2M to efficiently bind synthetic peptide. Thus, class I molecules on normal cells do not spontaneously bind or exchange peptides.

Abelson murine leukemia virus↗
PubMed1989

Mapping of epitopes recognized by alloreactive cytotoxic T lymphocytes using inhibition by MHC peptides.

To identify epitopes recognized by alloreactive CTL we have examined H-2Kb-specific CTL for their recognition of synthetic peptides with sequences derived from the native Kb class I molecule. Consecutive nested peptides spanning the immunogenic alpha 1 and alpha 2 domains of Kb were tested for their capacity to inhibit CTL clones in their recognition of cells expressing the native Kb molecule. Inhibition by these peptides was found to be an extremely rare event. One peptide (Kb.111-122) did inhibit recognition by one particular CTL clone, clone 13. Upon further investigation it was observed that clone 13 also recognized peptide Kb.111-122 when presented in the context of the syngeneic MHC molecule, Kd. Considering that residues 111 to 122 are located at the base of the antigen groove, and clone 13 is able to recognize Kb.111-122 when presented by syngeneic target cells, we suggest that inhibition of this CTL clone may be due to MHC restricted, self-presentation of peptide rather than to direct binding of free peptide to the TCR. Taken together, these results suggest inhibition of allospecific CTL by MHC peptides is a rare event at least for Kb recognition. Furthermore, they demonstrate the need for caution when interpreting inhibition by peptide as evidence for recognition by the TCR of the corresponding region on the native molecule.

Amino Acid Sequence↗
PubMed1989

Consequences of self-presentation of peptide antigen by cytolytic T lymphocytes.

We have used H-2Db-restricted CTL clones specific for peptide 365 to 380 of the influenza nucleoprotein to seek evidence for interaction between the TCR and peptide Ag. Preincubation of these CTL with peptide 365 to 380 resulted in inhibition of target cell lysis. In addition, CTL lysed allogeneic targets in the presence of soluble peptide Ag. Investigation of the basis of these two phenomena revealed a requirement for expression of H-2Db molecules by the effector cells. Either preincubation with anti-Db mAb or the use of chimera-derived H-2d CTL specific for Db plus peptide ablated both peptide-dependent inhibition and lysis of allogeneic cells, suggesting these activities are a consequence of self-presentation of peptide Ag by CTL. Lysis of allogeneic cells appears to represent bystander lysis by CTL in response to recognition of peptide on other effector cells. Lysis inhibition is attributable to a highly potent form of cold target inhibition in which CTL serve as their own cold targets.

Animals↗
PubMed1989

Cytolytic T-lymphocyte response to isolated class I H-2 proteins and influenza peptides.

T cells recognize antigenic peptides in the context of major histocompatibility complex (MHC) proteins. Peptide binding to class II MHC proteins, and T-cell recognition of these complexes at the functional level has been demonstrated. Although considerable evidence suggests that class I-restricted cytotoxic T lymphocytes (CTL) recognize class I-peptide complexes, this has not yet been directly demonstrated. Chen and Parham have recently detected a low level of direct binding of radiolabelled influenza peptides to class I HLA proteins, but the relevance of this binding to T-cell recognition remains uncertain. We report here that purified class I proteins pulsed with influenza peptides can trigger antigen-specific, TCR-mediated degranulation by CTL. Effective pulsing depends on both peptide concentration and time, and can occur within 60 minutes. These results provide strong support for the formation of an antigenic complex that is recognized by CTL in which peptide antigens are bound to isolated class I proteins.

Animals↗
PubMed1986

Lymphocyte subpopulations in the neonate: in vitro proliferation, IL-1 and IL-2 production by a subset of HNK-1-, OKT3-, OKT8+ lymphocytes displaying NK activity.

Neonatal lymphocytes include a subset of E-, OKT3-, OKT4-, OKT8+, HNK-1-, OKM1- cells displaying natural killer (NK) activity. More than 50% of these cells react with the B73.1 monoclonal antibody, moreover most of them bear the DR antigen, the receptor for Peanut agglutinin (PNA) and react with the OKT10 monoclonal antibody. This neonatal subset displays a higher NK activity than unseparated cord blood lymphocytes (CBL) and the present study shows that it is sensitive to boosting effect of IFN-B preincubation. When stimulated with T cell mitogens E-, OKT3-, OKT8+ CBL both produce Interleukin-2 (IL-2) and proliferate. Moreover this neonatal subset produces Interleukin-1 (IL-1) both spontaneously and in response to lipopolysaccharide (LPS). It has been previously suggested that these neonatal cells include a common precursor of NK and T cells. The present study further strengthen this hypothesis.

Antibodies, Monoclonal↗
PubMed1984

Lymphocyte subpopulations in the neonate: a subset of HNK-1-, OKT3-, OKT8+ lymphocytes displays natural killer activity.

It has been recently reported that cord blood lymphocytes (CBL) contain a subpopulation of OKT8+, sheep erythrocyte-rosetting negative (E-) cells not detectable in adult peripheral blood lymphocytes (a-PBL). The present studies were undertaken to characterize this subset of lymphocytes functionally and phenotypically. OKT8+ cells were purified from E-depleted CBL by negative selection on nylon-wool columns as well as by positive selection on plates coated with rabbit antibody to murine IgG (panning). The purified CBL displayed natural killer (NK) activity against K562 erythroleukemic cells. Although most of these CBL were large granular lymphocytes, they lacked typical NK markers such as HNK-1 and OKM1 surface antigens. Most OKT8+, OKT3- cells were also OKT10+, Ia+ and had the receptor for peanut agglutinin. These CBL may represent a stage along the differentiation pathway leading to mature NK or T cells.

Adult↗
PubMed1983

Recognition of influenza-infected cells by cytolytic T lymphocyte clones: determinant selection by class I restriction elements.

The fine specificity of virus recognition by influenza A/PR8/34(H1N1)-specific cytolytic T lymphocyte (CTL) clones was analyzed with the use of a panel of syngeneic target cells infected with five heterologous influenza A strain viruses. Forty-five H-2 D-end-restricted CTL clones from B10.A(5R) responders (Dd,Ld) demonstrated 14 different patterns of recognition. Many of these clonotypes were able to distinguish between closely related viruses of the same subtype. Such discriminatory capacity, however, was often accompanied by cross-reactivity against a distantly related viral subtype. This supports the contention that virus-specific CTL see different structures than do virus-specific antibodies. A similar analysis of the fine specificity of 60 Db-restricted clones from C57BL/6 responders was performed. The vast majority of this response was composed of clonotypes not observed in the B10.A(5R) response. In addition, the hierarchy of relatedness between the virus strain used for immunization and the various heterologous viruses was different in C57BL/6 and B10.A(5R). In contrast, the D-end-restricted response of Balb/c (Dd,Ld) demonstrated clonotypes similar to those found in B10.A(5R). These data suggest that determinant recognition in an anti-viral CTL response is a function of the H-2 restricting elements, and this is discussed in the context of determinant selection by class I molecules.

Animals↗
PubMed1983

Lymphocyte subpopulations in the neonate: identification of an immature subset of OKT8-positive, OKT3-negative cells.

T cell subpopulations of lymphocytes from cord blood (CBL) of 24 newborns and from peripheral blood (a-PBL) of 24 healthy adult volunteers were assessed in T cell-enriched, T cell depleted and unseparated lymphocyte fractions by using OKT3, 4, 6, and 8 monoclonal antibodies. The results show that T cell-enriched CBL include adult numbers of OKT3+, OKT4+, OKT6+ and OKT8+ lymphocytes whereas the T cell-depleted fraction consists of a high percentage of OKT8+, OKT3-, non-E rosette-forming cells bearing a PNA receptor. The presence of the PNA receptor and the lack of the OKT3+ antigen strongly support the hypothesis that the subset of OKT8+ cells in cord blood includes immature T lymphocytes that may represent an intermediate stage between thymocytes and mature peripheral T cells.

Adult↗
PubMed1982

Cell-mediated immunity in children with chronic cholestasis.

Cell-mediated immune response was evaluated in 14 children with long-lasting intra- or extrahepatic cholestasis. Cell-mediated immunity was clearly depressed in children with intrahepatic cholestasis while children with extrahepatic biliary obstruction had a more modest and variable degree of impairment. This finding may be related to the longer duration of cholestasis and the higher total bile acid level in the intrahepatic compared to the extrahepatic group. In particular, in children with Byler disease, long-lasting, severe intrahepatic cholestasis was associated with depressed cell-mediated immunity and recurrent severe infections.

Adolescent↗
PubMed1980

Activation of human peripheral blood lymphocytes: effect of concanavalin A and lipopolysaccharide on in vitro synthesis of DNA and immunoglobulins.

We studied the interaction of lipopolysaccharide (LPS) and concanavalin A (Con A) with regard to IgM and IgG production in in vitro cultures of human peripheral blood lymphocytes (PBL). In our system LPS alone over a wide range of concentrations did not stimulate detectable IgM or IgG production, while Con A at optimal (6 microgram/ml) and suboptimal (0.6 microgram/ml) mitogenic concentrations induced synthesis of small amounts of Ig. A marked enhancing effect was present when both Con A and LPS were added to the cultures. The different doses of LPS has similar effects on both classes of Ig, and typical dose-response curves were obtained. To evaluate the cellular basis of this synergism, the effect on cell proliferation was studied under identical experimental conditions in normal subjects and patients with X-linked agammaglobulinaemia (X-LA). Parallel cultures were set up after monocyte depletion by adherence on Petri dishes. On day 3, increasing doses of LPS were associated with progressive decreases in 3H-thymidine (3H-TdR) incorporation. Similar results were obtained with normal lymphocytes and those from X-LA patients. Monocyte depletion did not substantially alter the lymphocyte response pattern. The preferential induction of helper activities, either directly by helper stimulation or indirectly by suppressor inhibition, is suggested as a possible mechanism of the interaction observed.

Agammaglobulinemia↗
PubMed1980

Concanavalin A induces a T-cell dependent activation of human tonsil B cells in vitro.

Tonsillar lymphocytes cultured for 7 days in serum-supplemented RPMI-1640 medium were stimulated with Con A or PWM. IgM production was assessed by a hemagglutination inhibition assay. IgM was produced after Con A as well as PWM stimulation. Our data show that T-cell irradiation and/or addition of small numbers of T cells to the responding B-cell population facilitate(s) IgM synthesis. In particular in Con A-stimulated cultures the T-cell number is critical in regulating the appearance of suppressor effects. The results are discussed in terms of the various subpopulations possibly involved in the response to these mitogens.

B-Lymphocytes↗
PubMed1979

Plaque assay with protein A-coated erythrocytes for the evaluation of human immunoglobulin-secreting cells induced by pokeweed mitogen.

Cells secreting IgM, IgG and IgA were evaluated in cultures of human peripheral blood lymphocytes stimulated in vitro with pokeweed mitogen by a haemolytic plaque assay using protein A-coated erythrocytes in the presence of class-specific antisera. Kinetic study revealed that immunoglobulin-secreting cells appeared after 3 days of culture and peaked between days 5 and 7. IgM-secreting cells predominated throughout the culture period. This plaque assay is a useful and sensitive in vitro test for the evaluation of polyclonal B-cell activation in humans and may provide a good approach to the study of disturbances in the synthesis of the various classes of immunoglobulins.

Adult↗
PubMed1978

Polyclonal activation of human B lymphocytes in vitro by pokeweed mitogen: a simple technique for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production.

A simple technique has been worked out for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production from single cultures of 1 X 10(6) human peripheral blood lymphocytes stimulated with pokeweed mitogen (PWM). Kinetic studies showed that number of cells, thymidine incorporation rate, number of plaque-forming cells against fluorescein-isothiocyanate-haptenated sheep erythrocytes and concentration of IgM and IgG in the supernatant peaked on the average between day 5 and 7 of culture. This technique is particularly suitable for the analysis of hypogammaglobulinaemias in infancy.

Adult↗