Biomedical subjects

Randy R Brutkiewicz

Publications and source records attributed to Randy R Brutkiewicz.

27 records · Page 2Linked to original sources

PubMed2003

Defective presentation of the CD1d1-restricted natural Va14Ja18 NKT lymphocyte antigen caused by beta-D-glucosylceramide synthase deficiency.

Va14Ja18 natural T (NKT) cells play an immunoregulatory role, which is controlled by a self glycolipid(s) presented by CD1d. Although the synthetic antigen alpha-D-galactosylceramide (alpha-D-GalCer) stimulates all Va14Ja18 NKT cells, alpha-anomeric D-glycosylceramides are currently unknown in mammals. We have used beta-D-GalCer-deficient mice and beta-D-glucosylceramide (beta-D-GlcCer)-deficient cells to define the chemical nature of a natural NKT cell antigen. beta-D-GalCer-deficient mice exhibit normal NKT cell development and function, and cells from these animals potently stimulate NKT hybridomas. In striking contrast, the same hybridomas fail to react to CD1d1 expressed by a beta-D-GlcCer-deficient cell line. Importantly, human beta-D-GlcCer synthase cDNA transfer, and hence the biosynthesis of beta-D-GlcCer, restores the recognition of mutant cells expressing CD1d1 by the Va14Ja18 NKT hybridomas. Additionally, suppression of beta-D-GlcCer synthesis inhibits antigen presentation to Va14Ja18 NKT cells. The possibility that beta-D-GlcCer itself is the natural NKT cell antigen was excluded because it was unable to activate NKT hybridomas in a cell-free antigen-presentation assay. These findings suggest that beta-D-GlcCer may play an important role in generating and/or loading a natural Va14Ja18 NKT antigen.

Animals↗

PubMed2003

Myeloid marker expression on antiviral CD8+ T cells following an acute virus infection.

CD11b, CD11c, and F4/80 are normally used to define dendritic cell and/or macrophage populations. In this study, the expression of all three markers was observed on CD8(+) T cells following infection of mice with several distinct viruses. Using lymphocytic choriomeningitis virus as a model virus, it was found that relatively more CD11b(+)CD8(+) and CD11c(+)CD8(+) T cells were present in the periphery than in primary lymphoid organs; in contrast, the F4/80(+)CD8(+) T cell population was more prevalent in the spleen. All three myeloid markers were detected on virus-specific CTL. The expression of CD11b and CD11c on CD8(+) T cells correlated with their level of CTL activity, whereas the F4/80(+)CD8(+) T cell population increased after the peak of the CTL response but did not have higher CTL activity. These data suggest that there is a differential induction of CD11b, CD11c, and F4/80 on virus-specific CD8(+) T cells following an acute virus infection.

Acute Disease↗

PubMed2003

CD1d-mediated antigen presentation to natural killer T (NKT) cells.

CD1d molecules are lipid antigen-presenting molecules. They are involved in presenting these antigens to a unique subpopulation of T cells called natural killer T (NKT) cells, which have the capacity to produce both T helper (Th) 1 and Th2 cytokines. Thus, it is possible that the antigens presented by CD1d and/or the level at which they are presented could have profound effects on the immunoregulation of autoimmune and infectious diseases, as well as cancer. Because of the ability of CD1d-binding ligands to modulate NKT cell responses, targeting CD1d-mediated antigen presentation as a novel approach for new therapies in these and other diseases holds great promise.

Amino Acid Sequence↗

PubMed2002

Role of 4-1BB (CD137) in the functional activation of cord blood CD28(-)CD8(+) T cells.

The CD28(-) subset of CD8(+) T cells is associated with cytotoxic T lymphocyte (CTL) effector function. We investigated a potential role for 4-1BB, a costimulatory molecule structurally related to members of the tumor necrosis factor (TNF) receptor family, in the generation and functional activation of CD28(-) CTLs by using human cord blood (CB) cells composed exclusively of naive CD8(+) T cells with few or no CD28(-) CTLs. The 4-1BB was induced preferentially on the CB CD28(-)CD8(+) T cells when CD28 down-regulation was induced by interleukin 15 (IL-15) and IL-12 stimulation. Anti-4-1BB costimulation induced dramatic phenotypic changes in the CD28(-) CTLs, including restoration of CD28 expression as well as that of memory markers such as CD45RO and CC chemokine receptor 6 (CCR6). Anti-4-1BB costimulation also promoted long-term survival of CD28(-) CTLs, which were sensitive to activation-induced cell death upon anti-CD3 stimulation. The memory-type CD28(+) CTLs induced by anti-4-1BB costimulation acquired a greatly enhanced content of granzyme B, a cytolytic mediator, and enhanced cytotoxic activity as compared with CD28(-) CTLs. Strong cytotoxicity of memory-type CTLs to a 4-1BB ligand-expressing Epstein-Barr virus (EBV)-transformed B-cell line was almost completely abrogated by 4-1BB-Fc, a soluble form of 4-1BB, suggesting involvement of 4-1BB in cytolytic processes. Taken all together, our results suggest that 4-1BB plays a role in the differentiation of effector memory CTLs.

Antigens, CD↗

PubMed2002

Evidence for immune responses to a self-antigen in lung transplantation: role of type V collagen-specific T cells in the pathogenesis of lung allograft rejection.

We have reported that lung allograft rejection involves an immune response to a native protein in the lung, type V collagen (col(V)), and that col(V)-induced oral tolerance prevented acute and chronic rejection. In support of these findings col(V) fragments were detected in allografts during rejection, but not in normal lungs. The purpose of the current study was to isolate and characterize col(V)-specific allograft-infiltrating T cells and to determine their contribution to the rejection response in vivo. Two col(V)-specific T cell lines, LT1 and LT3, were isolated from F344 (RT1(lv1)) rat lung allografts during rejection that occurred after transplantation into WKY (RT1(l)) recipients. Both cell lines, but not normal lung lymphocytes, proliferated in response to col(V). Neither LT1 nor LT3 proliferated in response to alloantigens. LT1 and LT3 were CD4(+)CD25(-) and produced IFN-gamma in response to col(V). Compared with normal CD4(+) T cells, both cell lines expressed a limited V-beta TCR repertoire. Each cell strongly expressed V-beta 9 and 16, but differed in expression of other V-betas. Adoptive transfer of each cell line did not induce pathology in lungs of normal WKY rats. In contrast, adoptive transfer of LT1, but not LT3, caused marked peribronchiolar and perivascular inflammation in isograft (WKY) lungs and abrogated col(V)-induced oral tolerance to allograft (F344) lungs. Collectively, these data show that lung allograft rejection involves both allo- and autoimmune responses, and graft destruction that occurs during the rejection response may expose allograft-infiltrating T cells to potentially antigenic epitopes in col(V).

Animals↗

PubMed2002

Inhibition of glycolipid shedding rescues recognition of a CD1+ T cell lymphoma by natural killer T (NKT) cells.

Neoplastic transformation of cells is accompanied by an aberration of cell surface glycolipid composition. These tumor-associated, altered glycosphingolipids are often shed into the tumor cell microenvironment and mediate immunosuppressive activity. The nature and form of glycolipids shed by a variety of tumor cell lines and the mechanism(s) of shedding have been well characterized. The murine T cell lymphoma line, L5178Y-R, is known to shed a tumor-associated glycolipid, gangliotriaosylceramide, into the culture medium. We analyzed the effect of glycolipids from L5178Y-R on antigen presentation by murine CD1d1 molecules. CD1d1 molecules present glycolipid antigens to a specialized class of T cells called natural killer T (NKT) cells that mainly express a T cell receptor alpha chain (Valpha14Jalpha281) associated with Vbeta chains of limited diversity. In the current report, we found that L5178Y-R cells express CD1 on their cell surface yet are unable to stimulate CD1d1-specific NKT cells. We hypothesized that the glycolipid(s) shed by L5178Y-R inhibited antigen presentation by CD1d1. Pretreatment of CD1d1(+) cells with conditioned medium from L5178Y-R inhibited CD1-specific stimulation of canonical (Valpha14(+)) but not noncanonical (Valpha5(+)) NKT cells. Exogenous addition of lipids extracted from L5178Y-R cells as well as purified gangliotriaosylceramide mimicked this effect. Inhibition of glycolipid shedding in L5178Y-R cells with d-1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol resulted in the rescue of CD1d1 recognition by canonical (but not noncanonical) NKT cells. These results suggest that one means by which certain tumor cells can evade the host's innate antitumor immune response is by shedding glycolipids that inhibit CD1-mediated antigen presentation to NKT cells.

Animals↗

PubMed2002

Recycling CD1d1 molecules present endogenous antigens processed in an endocytic compartment to NKT cells.

Mouse CD1d1 molecules present endogenous glycolipids to NKT cells. Although glycolipid presentation requires CD1d1 transport through the endocytic pathway, the processing requirements for such endogenous Ag presentation by CD1d1 molecules are undefined. We examined CD1d1 Ag presentation to NKT cells by disrupting endocytic trafficking and function in cells expressing normal and mutated CD1d1 expressed by recombinant vaccinia viruses. Consistent with previous studies, we found that preventing CD1d1 localization to endosomes by altering its cytoplasmic targeting sequences abrogated recognition by Valpha14Jalpha281(+) NKT cells without affecting recognition by Valpha14(-) NKT cells. Increasing the pH of acidic compartments by incubating cells with chloroquine or bafilomycin A1 blocked CD1d1 recognition by Valpha14(+) (but not Valpha14(-)) NKT cells without reducing levels of cell surface CD1d1. Similar results were obtained with primaquine, which interferes with the recycling of cell surface glycoproteins. These results suggest that the loading of a subset of glycolipid ligands onto CD1d1 molecules entails the delivery of cell surface CD1d1 molecules and an acidic environment in the endocytic pathway.

Animals↗

PubMed2002

Lipid protein interactions: the assembly of CD1d1 with cellular phospholipids occurs in the endoplasmic reticulum.

CD1d1 is a member of a family of lipid Ag-presenting molecules. The cellular ligands associated with CD1d1 were isolated and characterized by biochemical means as an approach to elucidate the mechanism by which CD1 molecules assemble in vivo. Natural ligands of mouse CD1d1 included cellular phosphatidylinositol and phosphatidylinositol-glycans that are synthesized in the endoplasmic reticulum. Further biochemical data revealed that the two CD1d1 mutants, one defective in recycling from-and-to the plasma membrane and the other in efficiently negotiating the secretory pathway, associated with phosphatidylinositol. Thus phosphatidylinositol associated with CD1d1 in the early secretory pathway. Phosphatidylinositol also associated with CD1d1 in Pig-A-deficient cells that are defective in the first glycosylation step of glycosylphosphatidylinositol biosynthesis. Moreover, cellular phosphatidylinositol-glycans are not Valpha14Jalpha15 natural T cell Ags. Therefore, we predict that cellular lipids occlude the hydrophobic Ag-binding groove of CD1 during assembly until they are exchanged for a glycolipid Ag(s) within the recycling compartment for display on the plasma membrane. In this manner, cellular lipids might play a chaperone-like role in the assembly of CD1d1 in vivo, akin to the function of invariant chain in MHC class II assembly.

Animals↗

PubMed2002

Natural killer T (NKT) cells and their role in antitumor immunity.

Natural killer T (NKT) cells have become a major focus for those who study the innate immune response to tumors and infectious diseases, as well as autoimmunity. These novel T lymphocytes produce both Th1 and Th2 cytokines, recognize phospholipid and glycolipid antigens presented by CD1 molecules in a similar manner as peptides are recognized by cytotoxic T lymphocytes (CTL), and kill tumor cell targets by a perforin-dependent mechanism like NK cells and CTL. These ascribed functions thus demonstrate that NKT cells are a unique cytotoxic effector cell subpopulation with a kaleidoscope of activities. Because they can mediate antitumor effects in vivo with or without the collaboration of NK cells, the study of NKT cells in antitumor immunity may lead to novel treatments based on the ability to manipulate the generation and/or activity of these multifunctional lymphocytes.

Antigens, CD1↗