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J R Parnes

Publications and source records attributed to J R Parnes.

At least 55 records · Page 3Linked to original sources
PubMed1991

Enhancement of T-cell responsiveness by the lymphocyte-specific tyrosine protein kinase p56lck.

Lymphocyte-specific tyrosine protein kinase p56lck is physically associated with CD4 and CD8 T-cell surface molecules, suggesting that it may transduce CD4/CD8-triggered tyrosine phosphorylation signals during antigen stimulation. Indeed, antibody-mediated aggregation of CD4 (to mimic interaction with its ligand, major histocompatibility complex (MHC) class II molecules), rapidly elevates the kinase activity of p56lck and is associated with marked changes in tyrosine protein phosphorylation. Genetic analyses suggest that the interaction of CD4/CD8 with p56lck results in a positive signal during antigen-induced T-cell activation. To evaluate directly the role of p56lck in T-cell activation, we introduced a constitutively activated form of Lck protein (tyrosine 505 to phenylalanine 505 mutant); in a CD4-negative, MHC-class II restricted mouse T-cell hybridoma. We report here that, as for transfection of CD4, expression of the Lck mutant enhanced T-lymphocyte responsiveness. This finding provides direct evidence that p56lck can positively regulate T-cell functions and that it mediates at least some of the effects of CD4 and CD8 on T-cell activation.

Animals↗
PubMed1991

Identity of human Lyb-2 and CD72 and localization of the gene to chromosome 9.

We have recently reported the isolation of cDNA clones encoding the human homolog of the mouse B cell differentiation antigen Lyb-2. Expression of Lyb-2 is restricted to B lineage cells and turned off in antibody-secreting plasma cells in both mice and humans. Functional studies with anti-mouse Lyb-2 monoclonal antibodies (mAb) suggest that this protein may be involved in signals for B cell proliferation. We now describe the generation of mAb specific for human Lyb-2. Furthermore, we demonstrate that the human Lyb-2 protein is recognized by a mAb specific for the newly clustered pan B cell surface antigen CD72, which had been defined by mAb. Mouse L(tk-) cells expressing a transfected cDNA encoding human Lyb-2 bind a mAb specific for CD72. We further show that an antiserum and a mAb specific for human Lyb-2 and an anti-CD72 mAb immunoprecipitate the identical protein from human splenic B cells and B cell lines, as well as from transfected L(tk-) cells. These data indicate that CD72 is the human equivalent of mouse Lyb-2. We have additionally localized the gene for human Lyb-2/CD72 on the short arm of chromosome 9. Mouse Lyb-2 had been previously mapped to mouse chromosome 4. Lyb-2/CD72 is now the tenth gene known to be localized on human chromosome 9 and mouse chromosome 4.

Animals↗
PubMed1991

The roles of CD4 and CD8 in T cell activation.

CD4 and CD8 T cell surface molecules play a role in T cell recognition and activation by binding to their respective class II and class I major histocompatibility complex (MHC) ligands on an antigen presenting cell (APC). Though CD4 and CD8 are capable of binding to MHC molecules in the absence of the T cell receptor (TCR), increasing evidence suggests that they may primarily function by complexing with the TCR to form a 'co-receptor' for recognition of antigen-bound MHC. Using gene transfer studies we have demonstrated that CD4 and CD8 can augment antigen-induced IL-2 production through different mechanisms dependent on whether or not they can bind MHC independently of the TCR or complexed with the TCR. Under circumstances where CD4 and CD8 can bind to the same MHC ligand as the TCR, they potentiate antigen-induced IL-2 production maximally by a mechanism in large part dependent on their cytoplasmic tails. Enhancement of antigen-induced IL-2 production can also occur under circumstances where CD4 and CD8 bind on MHC ligand distinct from that recognized by the TCR. In this instance, the magnitude of this enhancement is not as great and appears (at least for CD8) to be independent of the cytoplasmic tail and the associated p56lck. The dependence of co-receptor function on the cytoplasmic tail of CD4 or CD8 may reflect the activity of the associated intracellular tyrosine kinase p56lck.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Identification of a human protein homologous to the mouse Lyb-2 B cell differentiation antigen and sequence of the corresponding cDNA.

We have isolated and sequenced cDNA clones encoding the human homolog of the mouse Lyb-2 B cell differentiation Ag. Previous data suggest that Lyb-2 might represent a growth factor or lymphokine receptor. Human Lyb-2 mRNA is expressed in normal human tonsils and bone marrow cells, in the pre-B cell line REH, in three Burkitt lymphoma cell lines, and in some EBV-transformed B cell lines, but not in antibody-secreting myeloma cell lines, T cell lines, or a promyelocytic leukemia cell line. These data indicate that expression of human Lyb-2 is restricted to B lineage cells and turned off in antibody-secreting plasma cells. A polyclonal mouse antiserum was raised against human Lyb-2 and immunoprecipitates a Mr 42,000 protein from REH, Raji, and Daudi cells and from mouse L(tk) cells transfected with the human Lyb-2 cDNA in an expression vector. The human Lyb-2 protein is related to both the asialoglycoprotein receptor and CD23, the B cell-specific FcR for IgE. These data demonstrate that human B cells express a previously undescribed cell surface protein that is homologous to mouse Lyb-2 and has a similar pattern of expression during B cell development.

Amino Acid Sequence↗
PubMed1990

Induction of tolerance in peripheral T cells with monoclonal antibodies.

Our goal has been to develop ways to tolerize the mature immune system to any defined antigen. In this report we show that peripheral (post-thymic) T cells of mice can become tolerant to a range of antigens (human and rat immunoglobulins, and bone marrow and skin grafts that differ at multiple minor transplantation antigens). In the case of human gamma globulin (HGG), this required that the antigen be given under the cover of a short course of non-depleting anti-CD4 antibody, while for tolerance to skin and marrow grafts anti-CD8 antibody was also required. Tolerance to HGG could be reinforced by repeated injections of HGG, but was lost in the absence of any further exposure to antigen. This reversal of tolerance with time was due to new T cells being exported from the thymus, as it was not observed in tolerized, adult thymectomized mice. In contrast, tolerance to marrow and skin grafts was permanent, presumably because the established grafts acted as a continuous source of antigen to reinforce the tolerant state. Tolerance could not be broken by the infusion of unprimed spleen cells and in one example (tolerance to Mls-1a) there was clear evidence that specific peripheral T cells were anergic. We propose that anergic cells may themselves participate in reinforcing the tolerant state by competing at sites of antigen presentation.

Animals↗
PubMed1989

Equivalence of human and mouse CD4 in enhancing antigen responses by a mouse class II-restricted T cell hybridoma.

We have examined the ability of hCD4 to interact functionally with mouse class II MHC molecules using the mouse T cell hybridoma BI-141, specific for beef insulin. We have previously shown that expression of mouse CD4 results in a marked enhancement of IL-2 release by BI-141 cells in response to beef insulin or, in a cross-reactive response, to pork insulin, on the appropriate mouse APCs. We now demonstrate that expression of hCD4 results in an equivalent stimulation of antigen responses by this mouse T cell hybridoma. The specificity of this effect was demonstrated by mAb and gp120 blocking studies. These data provide the first direct evidence for function of hCD4 and in an exclusively mouse system.

Animals↗
PubMed1989

Inability of CD8 alpha' polypeptides to associate with p56lck correlates with impaired function in vitro and lack of expression in vivo.

T-cell accessory molecules, particularly CD4 and CD8, seem to be involved in the control of T-cell activation by antigen. Precisely how such molecules operate is not fully understood, but evidence to date suggests a dual role, as receptors binding ligands on stimulator cells and by direct or indirect involvement in intracellular signalling events. In mouse, truncated 'tailless' CD8 molecules occur naturally (CD8 alpha' polypeptides) and although they are expressed on the surface of thymocytes, they are not expressed on the surface of mature T cells. In this study, we show that truncated CD8 molecules are impaired in their ability to interact with the protein tyrosine kinase, p56lck, and have decreased ability to restore immune responsiveness in vitro. Our data support a dual function for CD8 molecules correlated with expression of external domains and cytoplasmic domains, respectively. Both functions appear to be critical for a competent immune system in vivo.

Animals↗
PubMed1989

Sequence of the Lyb-2 B-cell differentiation antigen defines a gene superfamily of receptors with inverted membrane orientation.

Lyb-2 is a mouse B-cell differentiation antigen expressed on the surface of pre-B cells and B cells but not on terminally differentiated antibody-secreting plasma cells. Lyb-2 has been shown to play a role in B-cell activation and differentiation and may be a receptor for a B-cell growth factor or lymphokine. We have isolated and sequenced cDNA encoding the Lyb-2.1 allele. Lyb-2 mRNA is expressed only in B-lineage cells and is absent from antibody-secreting cell lines. The predicted protein contains 354 amino acids and is lacking an amino-terminal signal peptide. The protein is shown to be oriented with its carboxyl terminus external to the cell. Sequence comparisons demonstrate that Lyb-2 is homologous to the asialoglycoprotein receptor and to CD23, the B-cell-specific Fc receptor for IgE, both of which are oriented with their carboxyl termini external to the cell. These molecules, therefore, constitute a gene superfamily of cell surface receptors with inverted membrane orientation.

Amino Acid Sequence↗
PubMed1988

A second chain of human CD8 is expressed on peripheral blood lymphocytes.

Human CD8 has been thought to consist of disulfide-linked homodimers and homomultimers of a single polypeptide chain homologous to mouse and rat CD8 alpha. In contrast, mouse and rat CD8 are composed of disulfide-linked heterodimers of alpha and beta chains. We have now isolated and sequenced cDNA clones encoding a human homologue of mouse and rat CD8 beta. One such clone was inserted into an expression vector and its encoded product was shown to be expressed on the cell surface after cotransfection into L cells with the human CD8 alpha gene. A second form of human CD8 beta cDNA encoding a protein with an altered cytoplasmic tail was similarly transfected, but its product could not be demonstrated on the cell surface. CD8 beta was further shown to be expressed on the surface of almost all CD8+ human peripheral blood T cells. These data provide the first evidence that human CD8 is a heterodimeric protein.

Amino Acid Sequence↗
PubMed1988

Molecular linkage of the Ly-3 and Ly-2 genes. Requirement of Ly-2 for Ly-3 surface expression.

We have isolated the Ly-3 gene by chromosomal walking from the previously cloned Ly-2 gene. These genes are shown to be 36 kb apart and in the same transcriptional orientation. Transfection of the Ly-3 gene into mouse L cells results in cell surface expression of Ly-3 protein only in the presence of Ly-2 (or its human homolog, CD8), although Ly-2 surface expression is not similarly dependent on Ly-3. cDNA clones encoding Ly-3 have been isolated and sequenced and show little sequence similarity to Ly-2, whereas both Ly-2 and Ly-3 are homologous to Ig variable regions. One cDNA clone encodes a form of Ly-3 lacking a transmembrane region. Although two alleles of Ly-3 have been previously defined serologically, Northern blot analyses of Ly-3 mRNA from a series of inbred mouse strains show unusual polymorphisms in the lengths of Ly-3 mRNA species defining at least three allelic variants of this gene.

Alleles↗
PubMed1988

Acquisition of an additional antigen specificity after mouse CD4 gene transfer into a T helper hybridoma.

We have transfected the mouse CD4 gene into a beef insulin (BI)-specific murine T helper hybridoma that lacks CD4 surface expression. The CD4-expressing transfectants have acquired an additional reactivity for pork insulin (PI), which was not detectable in the original recipient cell. The transfectants' response to PI can be completely abrogated by anti-CD4 antibodies. The transfected clone showed a 50-fold increased sensitivity towards BI in comparison to the same CD4- hybridoma. These experiments suggest that CD4 may be important in determining the antigen fine specificity and, therefore, may also play a role in altering the T cell repertoire.

Animals↗
PubMed1988

Rescue of Daudi cell HLA expression by transfection of the mouse beta 2-microglobulin gene.

The Daudi cell line is a B-lymphoblastoid line derived from a Burkitt lymphoma. Daudi cells lack cell surface expression of class I HLA molecules despite the presence of intracellular class I heavy chains. They have a defect in the gene encoding beta 2-microglobulin (beta 2m), resulting in lack of translatable mRNA for this protein. It has been thought that this deficiency is responsible for the lack of cell surface class I expression. However, data have recently been presented demonstrating that at least one mouse class I heavy chain can be expressed on the cell surface in the absence of beta 2m. These results raised the questions of whether the lack of beta 2m is the only defect in Daudi and whether transfer of this single gene could restore surface class I expression. We found that transfection of the mouse beta 2m gene into Daudi indeed rescued cell surface expression of class I HLA molecules, and that these molecules could be recognized both by monomorphic and allospecific mAbs. CTL clones specific for HLA-B17 or a determinant shared by HLA-B17 and HLA-A2 killed the Daudi cells transfected with the beta 2m gene, but not untransfected Daudi or Daudi transfected with vector alone. Mouse beta 2m on the transfected Daudi cells could exchange with human beta 2m when the cells were incubated in human serum. This exchange did not alter the ability of the cells to be killed by the specific CTLs. These results demonstrate that the lack of beta 2m is the sole reason for lack of surface class I molecules in Daudi cells, and that beta 2m is required for cell surface expression of the specific class I heavy chains of Daudi.

Animals↗
PubMed1988

A CD8 polypeptide that is lost after passing the Golgi but before reaching the cell surface: a novel sorting mechanism.

The murine CD8 T cell differentiation antigen is a glycoprotein expressed on the cell surface as a heterodimer comprising the products of two closely linked genes, Ly-2 and Ly-3. The Ly-2 gene encodes, through a mechanism of alternate splicing, two polypeptide chains, alpha and alpha', that differ from one another in the lengths of their cytoplasmic tails. All T cells transcribe and translate both the alpha and alpha' polypeptides of Ly-2 and form heterodimers of each of these polypeptides disulphide-bonded with the Ly-3 polypeptide. However, there is very specific, developmentally controlled regulation of the expression of these heterodimers on the cell surface. Namely, immature T cells show no discrimination of CD8 molecules and express on their cell surface heterodimers containing the Ly-3 polypeptide linked to either the alpha or alpha' chain of Ly-2. In contrast, mature T cells express on their cell surface predominantly the heterodimer containing the Ly-2 alpha chain, the species which has a cytoplasmic tail. Moreover, in mature T cells the complexes which contain the alpha' chain are retained within the cell late in processing. These data emphasize the importance of the CD8 accessory molecule in the development of the functional T cell repertoire and uncover a novel protein sorting mechanism in mature T cells.

Amino Acid Sequence↗
PubMed1987

Reconstitution of MHC class I specificity by transfer of the T cell receptor and Lyt-2 genes.

The T cell receptor alpha and beta chain genes donated by an H-2 class I-specific, CD8-dependent cytotoxic T cell clone were transferred, alone or in combination with the Lyt-2 gene, into a class II-restricted, CD4+ T cell hybridoma. Two important points emerged. First, the alpha and beta T cell receptor genes endowed the recipient with the H-2 class I specificity of the donor only if the same cell had also been transfected with the Lyt-2 gene. Second, the functional Lyt-2 molecule was expressed on the transfected cells in the absence of the Lyt-3 polypeptide. These results demonstrate that, besides the T cell receptor, the Lyt-2 polypeptide is the only subset-specific molecule required to retarget a class II-reactive, CD4+ T cell line toward H-2 class I molecules.

Animals↗