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H R MacDonald

Publications and source records attributed to H R MacDonald.

At least 199 records · Page 11Linked to original sources
PubMed1988

Antigen recognition by H-2-restricted cytolytic T lymphocytes: inhibition of cytolysis by anti-CD8 monoclonal antibodies depends upon both concentration and primary sequence of peptide antigen.

While it is generally agreed that the specificity of the interaction between cytolytic T lymphocytes (CTL) and their target cells is controlled mainly by antigen-specific T cell receptors (TcR), the molecular role of cell surface CD8 molecules in this interaction is less well understood. In the present study we have reinvestigated the apparent contribution of CD8 molecules to the overall avidity of interaction between CTL and their targets by using a recently developed system of major histocompatibility complex (MHC) class I-restricted CTL clones that recognize defined peptide antigens. We demonstrate that under conditions where the density of MHC, TcR and accessory molecules remains constant, the susceptibility of CD8+ CTL to inhibition of cytolysis by anti-CD8 antibodies is highly dependent upon the concentration and primary structure of the peptide antigen. Although the precise role of the CD8 molecule remains unknown, our results are compatible with models that suggest its contribution to the overall avidity of the CTL-target cell interaction particularly in cases where the affinity between the TcR and antigen-MHC is low.

Animals↗
PubMed1988

Two monoclonal rat antibodies with specificity for the beta-chain variable region V beta 6 of the murine T-cell receptor.

Two rat monoclonal antibodies (mAbs), 44-22-1 and 46-6B5, which recognize an alloreactive cytotoxic clone, 3F9, have been further tested on a panel of T hybridomas and cytotoxic T-cell clones for binding and functional activities. The mAbs recognized only those cells sharing the expression of the T-cell receptor beta-chain variable region gene V beta 6 with 3F9. All V beta 6+ cells were activated by these mAbs under cross-linking conditions and their antigen-specific activation was blocked by soluble mAb. Furthermore, depletion of 46-6B5+ normal lymph node T cells eliminated all cells expressing the epitope recognized by 44-22-1 and V beta 6 mRNA.

Animals↗
PubMed1988

Macrophage activation in vitro by lymphocytes from Leishmania major infected healer and non-healer mice.

Peritoneal macrophages from CBA/T6 (healer) and BALB/c (non-healer) mice were infected with Leishmania major (LV39) in vitro. The microorganism replicated at the same rate in macrophages from either strain. Exposure of infected cells to lymph node cells (LNC) from infected syngeneic animals led to intracellular killing of the parasite by macrophages from both strains, provided LPS was present in the incubation medium. In vitro-propagated L.major-specific T-cell blasts activated macrophages from either strain in the absence of LPS. On a per cell basis, lymphoid cells from BALB/c mice were less efficient, however, than cells from CBA/T6 mice. Lysis of parasitized macrophages was also more marked in CBA/T6 than in BALB/c cell mixtures. LNC exposed to parasite antigen or to infected macrophages secreted macrophage-activating factor (MAF); incubation with antigen also induced lymphocyte proliferation. MAF production and LNC proliferation decreased with progression of the infection of BALB/c mice, but always remained significant. The reduction in relative T-cell numbers in the lymph nodes of infected animals was moderate; the absolute number of T-cells increased markedly in the lymphoid organs of both strains, however. These results suggest that failure to heal may coexist together with active cell-mediated immune response in non-healer mice.

Animals↗
PubMed1988

Appearance of granule-associated molecules during activation of cytolytic T-lymphocyte precursors by defined stimuli.

Lysis of target cells by cytolytic T lymphocytes (CTL) is associated with the exocytosis of cytoplasmic granules. Purified granules from CTL cell lines contain a pore-forming protein (perforin), tree serine esterases, granzyme A (60,000 MW), granzyme B (29,000 MW), and granzyme C (27,000 MW). We have compared the kinetics of appearance of cytolytic activity with that of perforin and granzyme A activity during activation of lymphocytes from normal animals with leukoagglutinin (LA) and recombinant interleukin-2 (rIL-2). Unstimulated lymph node cells do not express any of these activities, which appear between Day 3 and Day 4 of stimulation and increase rapidly to reach a pronounced peak on Day 6. On Day 7 all the activities are considerably lower, even though the cells still proliferate exponentially. There is a good correlation between the kinetics of appearance of all of these activities. Using antisera against perforin and against granzyme C, one can detect positive cytoplasmic granules in a small fraction of cells on Day 3; by Day 5, 80-90% of the cells are stained. This proportion decreases again on Day 7.

Animals↗
PubMed1988

Retargeting of cytolytic T lymphocytes by heteroaggregated (bispecific) antibodies.

The specificity and efficiency of tumor cell lysis by the retargeting of murine and human cytolytic T lymphocytes (CTL) with heteroaggregated (also known as bispecific or hybrid) antibodies were examined. Both murine and human CTL were capable of lysing various tumor cell targets in the presence of low concentrations of an appropriate heteroaggregated antibody. However, CTL (excluding clones) were lytic only when activated using reagents such as concanavalin A and interleukin 2 (IL2) with murine effector cells and with mitogenic mAb with human effector cells. The addition of IL2 (at 50-100 U/ml) did not cause enhanced lysis of the target cells used in the presence of heteroaggregated antibody with the murine effector cells. Furthermore, the lysis of target cells by heteroaggregated antibodies and CTL did not cause the lysis of bystander cells (cells not expressing an antigen recognized by the antibody that are mixed with the target cells). The efficient CTL-mediated lysis observed with these antibodies makes this a promising approach for the immunotherapy of human cancer.

Animals↗
PubMed1987

T cell lineages in the thymus of lpr/lpr mice. Evidence for parallel pathways of normal and abnormal T cell development.

Autoimmune mice homozygous for the lpr/lpr (lpr) gene develop a profound lymphadenopathy resulting from the accumulation of immature Thy-1+ Lyt-2- L3T4- cells in peripheral lymphoid tissues. The source of these cells is not known although the presence of a thymus is necessary to manifest both the lymph node enlargement and the autoimmunity. For this reason and the fact that the abnormal lpr cell phenotypically resembles immature thymocytes, we studied the thymus in lpr mice. Adult lpr thymuses were found to contain an immature population phenotypically identical to the peripherally accumulating cells, including the expression of B220 and Pgp-1 antigens as well as the presence of surface T cell receptor molecules as defined by the antibody KJ16-133. Evidence is presented that some of these lpr precursor T cells are capable of intrathymic differentiation, whereas the vast majority are exported unchanged to the lymph nodes where a portion differentiate further into mature T cells. This lpr-specific lineage could be distinguished from a normal component of the lpr thymus by surface phenotype and immunohistology. The results suggest that the massive accumulation of cells in lpr lymph nodes is not so much the result of abnormal proliferation of T cells as abnormal intrathymic differentiation. In addition, a minor subpopulation of normal Lyt-2- L3T4- thymocytes was identified that resembles the phenotype of the lpr cell and similarly expresses surface T cell receptor molecules. The presence of two parallel lineages in the lpr thymus thus also provides insight into normal T cell development.

Animals↗
PubMed1987

Lysis of tumor cells by the retargeting of murine cytolytic T lymphocytes with bispecific antibodies.

The specificity and efficiency of tumor-cell lysis by the retargeting of murine cytolytic lymphocytes (CTL) with bispecific antibodies was examined. Bispecific antibodies (also known as heteroaggregated or hybrid antibodies) were produced by the chemical coupling of monoclonal antibodies (MAbs) against H-2 antigens and the murine T-cell receptor (TCR). Murine tumor cell lines which expressed on their plasma membrane an antigen reactive with one component of the bispecific antibody were efficiently lysed in the presence of polyclonal murine CTL. CTL capable of lysis were generated by stimulating spleen or lymph-node cells with ConA and IL-2, while unstimulated cells or cells incubated only with IL-2 showed no lysis of target cells with bispecific antibodies. Furthermore, the lysis of target cells by bispecific antibodies and CTL did not cause the lysis of bystander cells (cells not expressing an antigen recognized by the antibody which are mixed with the target cells). The efficient CTL-mediated lysis observed with these antibodies makes this a promising approach for the immunotherapy of human cancer.

Animals↗
PubMed1987

A urine inhibitor of interleukin 1 activity that blocks ligand binding.

Urine from febrile patients was found to contain a novel inhibitor of interleukin 1 (IL-1) bioactivity that blocked the specific binding of radioiodinated IL-1 to its receptor in a dose-dependent fashion. Strong inhibition of IL-1 binding was still obtained when cells were preincubated with the inhibitor and washed, thus suggesting that the inhibitor binds to a surface structure (possibly the IL-1 receptor itself). The inhibitor was distinct from IL-1 as determined by both physical parameters (size and antigenicity) and receptor-binding characteristics (apparent affinity and dissociation rate). These data provide evidence for a physiologic regulator of IL-1 activity that functions in vivo via direct interference with ligand binding.

Animals↗
PubMed1987

Developmentally regulated expression of T cell receptor beta chain variable domains in immature thymocytes.

A minor subset of immature (CD4-,8-) thymocytes that lack expression of the B2A2 antigen was found to express low levels of surface TCR protein as detected by mAbs F23.1 and KJ16 (reacting with protein products of the V beta 8 gene family). Interestingly, F23.1/KJ16 determinants were expressed on a two- to three-fold higher proportion of B2A2- thymocytes than mature lymph node T cells in four independent haplotypes. When expanded in short-term culture with PMA and calcium ionophore, B2A2- thymocytes retained their overexpression of F23.1/KJ16 determinants and showed a fivefold elevated level (relative to lymph node) of V beta 8-specific mRNA. Taken together, these findings suggest that expression of TCR V beta genes, like Ig genes, is developmentally regulated.

Animals↗
PubMed1987

Identification of the plasma membrane receptor for interleukin-1 on mouse thymoma cells.

The plasma membrane receptor for interleukin-1 (IL-1) has been characterized from mouse EL4-6.1 thymoma cells. Following binding of IL-1 to surface labeled EL4-6.1 cells, the IL-1 binding molecule was immuno-precipitated using a rabbit antiserum against the hormone. The putative IL-1 receptor is a membrane-associated glycopeptide of Mr = 82,000 containing probably two or three N-linked glycan units as indicated by its conversion into a Mr = 60,000 polypeptide upon deglycosylation with endo-beta-N-glycosidase F.

Animals↗
PubMed1987

T cell antigen receptor expression in athymic (nu/nu) mice. Evidence for an oligoclonal beta chain repertoire.

The expression of T cell antigen receptors (TCR) in congenitally athymic (nude) mice has been investigated. Lymph node T cells from 4-5-mo-old athymic mice expressed full-length transcripts for the TCR alpha and beta chains at a level two-to three-fold lower than normal littermate (nu/+) controls. Low levels of expression of TCR protein at the surface of a proportion of nude T cells was demonstrated by staining with monoclonal antibodies KJ16-133 and F23.1 (directed against protein products of a family of TCR beta chain variable region genes known as V beta 8). Immunoprecipitation studies confirmed that F23.1 reacted with a similar molecular species on nude and nu/+ T cells. Studies with individual nude mice revealed a striking heterogeneity in the proportion of T cells expressing KJ16/F23.1 that was not seen in normal animals. This heterogeneity correlated with the expression of mRNA specific for V beta 8 but not with total expression of full-length beta chain transcripts. Analysis of Lyt-2+ and L3T4+ T cell subsets in individual nude mice further demonstrated that F23.1 expression was frequently associated with only one subset, and several cases were seen in which all L3T4+ cells expressed F23.1. In contrast, a similar (and constant) proportion of Lyt-2+ or L3T4+ T cells expressed F23.1 in control mice. Southern blotting of Hind III-digested DNA from nude T cells with a C beta probe revealed a more restricted pattern of TCR beta chain rearrangements than was seen for normal T cells. Taken together, these data provide compelling evidence that TCR gene rearrangement and expression can occur extrathymically. Furthermore, they suggest a model according to which the restricted functional repertoire of T cells previously observed in individual nude mice results from an oligoclonal expansion of T cells that have randomly rearranged and expressed TCR beta chain genes.

Animals↗
PubMed1987

Distinction of virgin and memory T lymphocytes. Stable acquisition of the Pgp-1 glycoprotein concomitant with antigenic stimulation.

The Pgp-1 glycoprotein was identified on a minor (27%) subset of peripheral Lyt-2+ or L3T4+ T cells. In contrast, mature medullary-type thymocytes (Lyt-2+ L3T4-, Lyt-2- L3T4+) were nearly devoid of cells expressing detectable surface Pgp-1. The appearance of peripheral Pgp-1- T cells was found to be thymus dependent, as demonstrated by the diminished proportion of Pgp-1- T cells after thymectomy and their virtual absence in athymic nude mice. The subsequent acquisition of surface Pgp-1 was found to be a stable differentiation event occurring concomitantly with primary antigenic stimulation; selected Pgp-1- mature T cells from thymus or periphery acquired constitutive expression of Pgp-1 after stimulation in vitro with alloantigen or mitogens. These observations were extended by studies in vivo showing that immunization with various antigens augmented the percentage of Pgp-1+ spleen cells within the Lyt-2+ subset. Furthermore, the frequencies of antigen-specific CTLp, after immunization by any of three different antigens tested, were greatly enriched in the Pgp-1+ compared with the Pgp-1- subpopulations. Peritoneal exudate Lyt-2+ cells, after a localized allograft rejection, demonstrated a particularly prominent Pgp-1+ subpopulation (78%) that contained virtually all the allospecific cytolytic activity. A model consistent with all of these data proposes that mature thymocytes lacking surface Pgp-1 upon emigration to the periphery acquire its expression at the time of primary antigenic stimulation. Hence, expression of Pgp-1 among peripheral T cells is an important differentiation marker for identifying antigen-stimulated memory T cells.

Animals↗
PubMed1987

N-terminal-methionylated interleukin-1 beta has reduced receptor-binding affinity.

The receptor-binding affinity of recombinant-derived interleukin-1 beta containing unprocessed N-terminal methionine (MAPV-) was 10-fold lower than protein containing the authentic N-terminal sequence (APV-). Structural analysis of the methionylated and non-methionylated proteins by NMR spectroscopy detected no (or minor) conformational differences. The differences in binding affinity, therefore, suggest that the additional N-terminal methionine causes a small, direct or indirect, perturbation of the receptor-binding region.

Escherichia coli↗
PubMed1987

Abnormal expression of T cell receptor genes in Lyt-2- L3T4- lymphocytes of lpr mice: comparison with normal immature thymocytes.

The autoimmunity and lymphoproliferation characteristic of lpr mice are age and thymus dependent. The accumulating Lyt-2- L3T4- T cells express only minimal cell-surface antigen receptor. After stimulation with phorbol myristic acetate (PMA) and interleukin 2, essentially normal levels of surface antigen receptor were expressed by the lpr Lyt-2- L3T4- subpopulation but remained undetectable in the corresponding normal immature thymocyte population. We have found near normal T cell receptor (TCR)-alpha and -beta mRNA expression by these lpr cells. The phenotypically comparable Lyt-2- L3T4- subset of normal thymocytes expressed approximately 10-fold less TCR-alpha mRNA than normal lymph node cells and somewhat higher TCR-beta mRNA. After cultivation of this immature thymocyte subpopulation with PMA and interleukin 2, TCR-alpha mRNA levels remained low, and TCR-beta transcripts were found to be subnormal. By using the same culture conditions, the corresponding mRNA levels of the lpr subset tended to resemble those of Lyt-2- L3T4- thymocytes. Fresh and cultured Lyt-2- L3T4- normal thymocytes showed comparably high levels of full-length TCR-gamma transcripts. In contrast, the fresh lpr subset had barely detectable levels of TCR-gamma mRNA. Upon cultivation, however, these levels increased over 200-fold to within the range observed in the Lyt-2- L3T4- thymocyte subset. No induction of the gamma gene was observed in similarly cultured normal lymph node T cells. The lpr cells may therefore correspond to an as yet undefined stage of normal T cell differentiation.

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