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A Finnegan

Publications and source records attributed to A Finnegan.

54 records · Page 3Linked to original sources
PubMed1989

A single amino acid mutation in a protein antigen abrogates presentation of certain T cell determinants.

Nase-specific T cell recognize the 86-100 peptide in association with B10.A APC. Clone N40 recognizes the 86-100 peptide in association with B10.A (Ek alpha Ek beta) and B10.A (5R) (Ek alpha Eb beta) APCs. We demonstrate here that a single amino acid substitution in the staphylococcal nuclease protein alters the structure of the processed peptide such that the T cell epitope recognized by clone N40 was only available for recognition in conjunction with B10.A (5R) but not the B10.A APCs. Other Nase-specific T cells recognize the mutant nuclease, and a synthetic peptide corresponding to the immunodominant region of the mutant protein was stimulatory for all the Nase-specific T cells. These results suggest that the mutation either affects the processing of the protein into antigenic peptides or affects the conformation of the processed fragment differently from that of the peptide.

Animals↗
PubMed1989

Sequences outside a minimal immunodominant site exert negative effects on recognition by staphylococcal nuclease-specific T cell clones.

In recent years, synthetic peptides have been utilized extensively to characterize the minimal essential immunodominant sites on model protein Ag. However, little work has focused on the effect that sequences flanking these minimal recognition sites may exert on T cell recognition. Previous work with staphylococcal nuclease (Nase) demonstrated that I-Ek-restricted clones recognize the peptide 81-100, whereas I-Ab-restricted clones recognize the over-lapping but non-cross-reacting peptide 91-110. Further analysis with 15 or 10 residue peptides within the region 81-110 reveals that the minimal sequence capable of stimulating I-Ek-restricted clones is contained within the decapeptide 91-100. Addition of residues 86-90, to give the peptide 86-100, enhanced the recognition substantially, whereas addition of residues 101-105 produced a 91-105 peptide with no stimulatory ability. These results suggest that interactions between the antigenic peptide 91-100 and residues within the flanking 101-105 sequence have negative consequences for presentation of the immunodominant epitope to T cell clones. Introduction of single amino acid substitutions within 91-105 produced peptides that induce responses comparable to those seen with 91-100. These results are consistent with the suggestion of negative interactions between the minimal immunodominant site and flanking sequences in that single residue substitutions may remove these negative interactions and lead to restoration of stimulatory ability. The negative effect of flanking sequences on T cell recognition of immunodominant sites presents new considerations for development of synthetic vaccines as well as for understanding the biology of Ag processing and presentation.

Amino Acid Sequence↗
PubMed1988

IL-1 is an autocrine growth factor for T cell clones.

Activation of Th lymphocytes requires that Ag be presented on the surface of accessory cells displaying Ia Ag. A number of studies have concluded that the T cell also requires IL-1 from accessory cells. However, we recently reported that one murine T cell clone (D10.G4.1) produced its own IL-1-like activity after encountering APC (9). In this report, we demonstrate that 1) IL-1 production is a common property of murine T cell clones, 2) T cell IL-1 activity is blocked by anti-IL-1-alpha antiserum, 3) IL-1-alpha mRNA can be directly visualized in individual cloned T cells using in situ hybridization techniques, and 4) IL-1 appears to serve an autocrine role in the activation of T cell clones inasmuch as anti-IL-1-alpha antiserum blocks cell proliferation when the T cell is the only IL-1 source.

Animals↗
PubMed1987

Induction of IgG2a secretion from mIgG2a+ B-lymphoid tumor cells by BCDF present in several antigen-specific T-helper clones.

In order to study the soluble factor(s) that play an important role for the differentiation of IgG2-secreting B cells, we examined whether membrane IgG2a (mIgG2a)-bearing BALB/c B-lymphoid tumor cells, A20, could be induced to secrete IgG2a after treatment with soluble factors. We detected a potent B-cell differentiation activity inducing the Ig secretion of A20 tumor cells (BCDF-A20) in supernatants of several soluble antigens as well as alloantigen-specific T-cell clones of various genetic backgrounds. Thus, this BCDF-A20 activity was working in an antigen-nonspecific and MHC-nonspecific manner and abundant in many T-cell clones. It was shown that neither interleukin 1, interleukin 2, interferon, T-cell replacing factor, B-cell maturation factor, nor B-cell stimulatory factor-1 alone had any significant effect on the induction of Ig secretion of A20 tumor cells. Using isotype-specific rabbit anti-mouse Ig developers, we showed that mIgG2a+ A20 tumor cells secreted IgG2a after the treatment with soluble factors. The peak of the response of A20 tumor cells to BCDF-A20 was obtained 3 days after the treatment with culture supernatants of T-cell clones. In this study, we have clearly shown that mIgG2a+ A20 tumor cells were able to secrete IgG2a after treatment with T-cell soluble factors.

Animals↗
PubMed1986

The T cell repertoire for recognition of a phylogenetically distant protein antigen. Peptide specificity and MHC restriction of staphylococcal nuclease-specific T cell clones.

Previous studies (1) have indicated that the repertoire of murine T cells specific for a potentially complex protein antigen is in fact specific for a limited number of antigenic epitopes on that antigen in association with a given Ia molecule. Since those studies generally analyzed responses to antigens that differ in only a few amino acids from homologous murine molecules, it was possible that tolerance to self proteins was responsible for the limited T cell repertoire seen in responses to closely related proteins. It was therefore of interest to determine whether T cell recognition of a structurally and phylogenetically more distant protein molecule would also show specificity for a limited number of immunodominant peptides on that molecule. A series of experiments was designed to study the antigen fine specificity and MHC restriction of T cell clones specific for the bacterially derived antigen staphylococcal nuclease (Nase). T cell clones generated in (H-2b X H-2a)F1 (B6AF1) T cells were shown to be specific for Nase and to be restricted by either Ab alpha Ab beta or Ek alpha Ek beta. The fine specificity of these clones was then analyzed using cyanogen bromide and tryptic fragments and a series of overlapping 20-amino-acid synthetic peptides corresponding to and spanning the entire sequence of the Nase molecule. Two Ab alpha Ab beta-restricted clones were highly responsive to peptide 91-110, and not to other synthetic Nase peptides. In contrast, seven Ek alpha Ek beta-restricted clones were consistently responsive to peptide 81-100 and not to 91-110 or to other Nase peptides. Certain of these Ek alpha Ek beta-restricted T cells expressed an interesting crossreactivity, in that they responded to peptide 51-70 as well as to 81-100, although the response to 51-70 was characterized by a markedly shifted dose-response curve, indicating a reduced efficiency of activation by this peptide. Analysis of the amino acid sequences of these regions indicates that this unexpected crossreaction may have a structural basis. A single Nase-specific T cell line generated from BALB/c T cells was, in contrast to any of the B6AF1 clones studied, responsive only to peptide 61-80 and not to other peptides, including 81-100 or 91-110. Collectively, these findings show that Nase-specific T cells are responsive to discrete Nase peptides. Moreover, the present findings suggest that in T cell recognition of a complex and highly foreign protein antigen, a limited number of peptide epitopes are preferentially recognized by T cells in association with a given Ia molecule.

Amino Acid Sequence↗
PubMed1986

Antigen-induced T suppressor cells regulate the autoreactive T helper-B cell interaction.

The T suppressor (Ts) cell population that functions to regulate antigen-specific MHC-restricted T helper (Th)-B cell interactions also regulates the activation of B cells by cloned autoreactive Th cells. Activated Ts cells were generated by in vivo priming and restimulation in vitro with high concentrations of the specific priming antigen. Once generated, this Ts population inhibits the Th-dependent activation of primed B cells by both antigen-specific and autoreactive T cells in an antigen-nonspecific manner. This suppression requires the participation of both Lyt-1+2- and Lyt-1-2+ T cells. It was also demonstrated that accessory cells were required for the induction of Ts cells. Moreover, the generation of suppression was MHC-restricted and required the recognition by T cells of Ia antigens on accessory cells. These studies demonstrate that the same or a very similar Ts cell population can function to inhibit the activation of B cells by antigen-specific as well as autoreactive T cells.

Animals↗
PubMed1986

Studies of glomerular mesangial uptake and processing of macromolecules. I. Effect of polyvinyl alcohol-induced macrophages on uptake of iron dextran.

The influence of prior glomerular mesangial uptake of a macromolecule that induces the infiltration of macrophages (M phi) into the mesangium on the uptake of a second macromolecule by the mesangium was studied in inbred Lewis rats. Renal transplantation of kidneys from rats previously injected with polyvinyl alcohol (PVA) was performed to avoid the potential influences of ongoing uptake of PVA and altered host milieu on the glomerular uptake of iron dextran (ID), a macromolecule that localizes primarily in the intrinsic mesangial cells of unmodified rats. In contrast to that in the recipient's native kidney, the uptake of ID was markedly increased in the glomeruli in kidneys previously exposed to PVA. This enhanced uptake was the consequence of the phagocytic activity of mesangial M phi elicited by and containing PVA since the site of increased ID content was shown by ultrastructural studies to be within mesangial M phi. Isogeneic renal transplantation per se did not influence mesangial function since the glomerular uptake of ID in donor and recipient kidneys was the same when donors were normal rats. In addition to the enhanced uptake of ID into lysosomes by mesangial M phi these cells were also much more active in the further processing of ID to ferritin particles within the cytoplasm than were intrinsic mesangial cells. These studies demonstrate that M phi attracted to the mesangium by a stimulus such as PVA may have important effects on the consequences of additional challenges to the mesangium.

Animals↗
PubMed1985

Antigen processing requirements for T cell activation: differential requirements for presentation of soluble conventional antigen vs cell surface MHC determinants.

The present studies were undertaken to characterize the antigen-processing requirements involved in the responses to T cells to soluble antigen (antigen specific), to allogeneic cell surface MHC determinants (alloreactive), and to syngeneic MHC determinants (autoreactive). T cell clones were used that have dual cross-reactive specificities either 1) for self MHC plus soluble antigen and for allogeneic MHC products or 2) for syngeneic MHC and for allogeneic MHC, in order to permit comparison of the processing requirements for responses of the same T cell to distinct antigenic stimuli. The proliferative responses of antigen-specific, Ia-restricted T cell clones to soluble antigens were sensitive to treatment of antigen-presenting cells (APC) with 125 to 250 microM chloroquine, a lysosomotropic agent previously shown to inhibit the processing of soluble antigens. In contrast, the same T cell clones were only minimally affected in their ability to respond to similarly chloroquine-treated APC expressing allogeneic MHC products. The responses of autoreactive T cell clones to syngeneic stimulating cells and their cross-reactive responses to allogeneic cells were both resistant to chloroquine treatment of stimulating cells. The failure of chloroquine to inhibit antigen presentation to autoreactive T cell clones suggests that these clones are specific for self Ia not associated with in vitro processed foreign antigen. Thus, chloroquine sensitivity distinguishes the in vitro antigen-processing requirements for presentation of the soluble antigens tested from the requirements for presentation of syngeneic or allogeneic cell surface MHC determinants to the same T cells.

Animals↗
PubMed1984

Activation of B cells by autoreactive T cells: cloned autoreactive T cells activate B cells by two distinct pathways.

Although the existence of autoreactive T cells has been widely reported, the functional capacities of these populations have been less well defined. Studies were therefore carried out to characterize the relationship of autoreactive T cells to antigen-specific major histocompatibility complex (MHC)-restricted T cells in their ability to act as helper cells for the induction of immunoglobulin synthesis by B cells. A number of autoreactive T cell lines and clones were isolated from antigen-primed spleen and lymph node cell populations. Autoreactive T cells were found to proliferate in response to direct recognition of syngeneic I-A or I-E subregion-encoded antigens in the absence of any apparent foreign antigen. It was shown that cloned autoreactive T cells were capable of activating B cell responses through two distinct pathways. After appropriate stimulation by syngeneic cells, autoreactive T cells polyclonally activated primed or unprimed B cells to synthesize IgM antibodies. These activated T cells functioned in these responses through an MHC-unrestricted pathway in which polyclonal responses were induced in both syngeneic and allogeneic B cells. These cloned autoreactive T cells were also able to activate IgG responses by primed B cells through a different activation pathway. In contrast to the polyclonal activation of IgM responses, the induction of IgG antibodies by the same cloned T cells required primed B cells and stimulation with the priming antigen. The activation of B cells to produce IgG was strongly MHC restricted and required the direct recognition by the autoreactive T cells of self MHC determinants expressed on the B cell surface, with no bystander activation of allogeneic B cells. These results indicate that cloned autoreactive T cells resemble antigen-specific MHC-restricted T cells in their ability to function as T helper cells through distinct MHC-restricted and MHC-unrestricted pathways.

Animals↗
PubMed1984

An analysis of functional T cell recognition sites on I-E molecules.

The recognition of I-E molecules by antigen-specific T cells was studied to determine if one or multiple topographic sites on the I-E molecules can function as restricting elements for T cells. A panel of 14 I-Ek-specific monoclonal antibodies (mAb) was used to inhibit T cell proliferation induced by antigens, the recognition of which was restricted by I-E-encoded determinants. These antibodies gave patterns of inhibition that were similar for three long-term antigen-specific T cell lines. Multiple distinct patterns of inhibition, however, were observed when a series of antigen-specific I-E-restricted T cell clones was studied. Differences were identified even among clones expressing apparently similar antigen specificities and MHC restriction. The observed inhibition by these antibodies appeared to be caused by specific steric or allosteric interference with T cell recognition of antigen and Ia. Based on the differences in patterns of inhibition, it was possible to infer the existence of distinct sites or conformations on the I-E molecule that are functionally involved in antigen-specific T cell recognition.

Animals↗
PubMed1981

Ly-18, a new alloantigen present on cytotoxic T cells and controlled by a gene(s) to the Igh-V locus.

Antiserum raised in allotype-congenic mice recognizes a T cell differentiation antigen designated Ly-18. This antiserum was raised by immunization of (CB.20 x CBA-Igh-1b)F1 mice with secondary BALB/c anti-CBA allospecific cytotoxic cells. This antigenic specificity is expressed on cytotoxic T cells but not on cells proliferating in an MLR, plaque-forming cells specific for SRBC, or resting lymphoid cells. The expression of Ly-18 is controlled by gene(s) linked to the VH gene complex of Igh-1 allotype strains. There is no evidence at present for MHC gene control. Unlike other putative antibodies against antigen receptors, anti-Ly 18 does not block cytotoxicity. In addition, Ly-18 expression is not altered by the antigenic specificity of the Igh-1 effector. We conclude Ly-18 is a differentiation antigen present on a subpopulation of activated T cells. The gene(s) that codes for expression of Ly-18 is linked to the expression of Igh-1 genes.

Animals↗
PubMed1979

A mature T lymphocyte subpopulation marker closely linked to the Ig-1 allotype Ch locus.

An antiserum raised in BALB/c AnN mice against selected CAL.20 T cells reacts with a cell surface antigen in virgin animals that is found on 25% of mature thymocytes and Lyt-2-bearing T cells, but not on prothymocytes, Lyt-1 T cells or B cells. The antigen is restricted to strains carrying the Ig-1d or Ig-1e heavy chain allotype haplotypes. It is expressed in F1 mice. The antiserum blocks the binding of suppressor T cells to the cross-reacting idiotype for arsonate while reagents specific for Fab, Fc or Ig were ineffective. We suggest that the antigen described represents a determinant on the product of a new locus coding for a heavy chain-linked polypeptide found on a subpopulation of T cells.

Animals↗
PubMed1978

Enhancement of cardiac allografts in rats. Comparison of host responses to different treatment protocols.

Immunological responses to heterotopic (L X BN)F1 cardiac allografts placed in untreated L rats were compared with those grafts enhanced by different treatment regimens. Host pretreatment by antigen and antibody (Ag-Ab) 11 and 10 days before transplantation, respectively, was the most effective treatment regimen for prolongation of graft function; active or passive immunization alone increased survival only modestly. A late dose of antiserum administered to Ag-Ab-pretreated animals significantly shortened graft survival. Patterns of cellular responsiveness were measured serially by lymphocyte-mediated cytotoxicity; humoral immunity by Ab-lymphocyte-mediated cytotoxicity, capillary hemagglutination, and complement-dependent cytotoxicity. Allograft rejection in animals of all groups was heralded in vitro by increasing immunological activity. All cellular and humoral responses were depressed consistently in Ag-Ab-pretreated recipients. Cellular but not humoral responses were decreased in Ag-pretreated hosts, while humoral but not cellular responses were decreased in Ab-treated animals. The results suggest that the in vitro determinants of immunological activity used in this study generally followed clinical patterns of rejection or enhancement of cardiac allografts in the rat. Recipient pretreatment with Ag and Ab is more effective in graft prolongation than treatment with Ag or Ab alone, and in vitro data suggest an additive effect of these two regiments.

Animals↗
PubMed1976

A procedure for the bulk preparation of brain microsomes with low speed centrifugation.

A method is described for the rapid isolation of microsomes from brains of various species. The method depends on the interaction of calcium with microsomes. The procedure is limited because calcium inhibits certain microsomal enzymes. Magnesium and manganese may be substituted for calcium. However, the substitutions decrease the reliability and efficiency of the procedure.

Animals↗