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R L Modlin

Publications and source records attributed to R L Modlin.

At least 55 records · Page 3Linked to original sources
PubMed1998

IL-15 enhances the response of human gamma delta T cells to nonpeptide [correction of nonpetide] microbial antigens.

Human gamma delta T cells have the ability to rapidly expand and produce IFN-gamma in response to nonpeptide Ags of microbial pathogens, in particular a class of compounds known as the prenyl phosphates. We investigated the ability of IL-15, a T cell growth factor, to modulate prenyl phosphate-induced gamma delta T cell proliferation and cytokine production. IL-15 significantly enhanced the expansion of gamma delta T cells in the peripheral blood after stimulation in vitro with isopentenyl pyrophosphate. Moreover, using gamma delta T cell clones, we determined that IL-15-induced T cell proliferation was dependent on the IL-2R beta chain but not the IL-2R alpha chain. We therefore studied the IL-15R alpha chain expression in human gamma delta T cells in the presence or absence of nonpeptide Ags. We found IL-15R alpha mRNA expression in IL-15-stimulated and Ag-stimulated human gamma delta T cells but not in resting gamma delta T cells. Although IL-15 itself had little effect on the production of IFN-gamma, IL-15 plus IL-12 acted synergistically to augment IFN-gamma production by gamma delta T cells. Moreover, we showed that this increase in IFN-gamma could be explained by the dual activation of STAT1 and STAT4 by IL-15 and IL-12, respectively. Taken together, these results suggest that IL-15 may contribute to activation of human gamma delta T cells in the immune response to microbial pathogens.

Antigens, Bacterial↗
PubMed1998

Isolation of mycobacterium-reactive CD1-restricted T cells from patients with human immunodeficiency virus infection.

Because CD1-restricted T cells lack CD4 but produce IFN-gamma in response to nonpeptide mycobacterial antigens, they could play a unique role in immunity to tuberculosis. We studied CD1-restricted T cells in the context of HIV infection by expanding CD4(-) T cell lines from 10 HIV-infected patients. Upon stimulation with Mycobacterium tuberculosis antigen or upon exposure to macrophages infected with M. tuberculosis, these T cell lines proliferated, produced IFN-gamma, and showed cytolytic T cell (CTL) activity against macrophages pulsed with mycobacterial antigen, findings consistent with a protective role against M. tuberculosis. Anti-CD1b antibodies abrogated T cell proliferation, IFN-gamma production, and CTL activity, demonstrating that these T cells are CD1 restricted. IFN-gamma production in response to M. tuberculosis was enhanced by antitransforming growth factor-beta in 8/10 lines, and by IL-15 in 2/10 lines. IFN-gamma production was augmented in a nonantigen-specific manner by IL-12 in 4/8 lines. When live HIV was cocultured with CD1-restricted T cell lines, p24 antigen and proviral DNA were not detected, indicating that the T cells were not infectable with HIV. Vaccination strategies aimed at activation and expansion of M. tuberculosis-reactive CD1-restricted T cells in HIV-infected patients may constitute a novel means to provide protection against tuberculosis, while minimizing the risk of enhancing HIV replication through stimulation of CD4(+) cells.

Antigens, CD1↗
PubMed1998

Expression of interleukin-12 in synovial tissue from patients with rheumatoid arthritis.

OBJECTIVE: To examine the importance of interleukin-12 (IL-12) as a factor in the interferon-gamma (IFNgamma)-dominant T cell cytokine response in the synovial tissue of patients with rheumatoid arthritis (RA). METHODS: The expression of IL-12 in synovial tissue samples from patients with chronic RA (> or = 2 years) was compared with that in samples from osteoarthritis (OA) patients by detection of IL-12 p40 messenger RNA (mRNA) using reverse transcriptase-polymerase chain reaction, measurement of IL-12 p70 protein in culture supernatants of tissue cells by immunoassay, and immunostaining of tissue sections with anti-IL-12 p70. The production of IFNgamma by RA synovial tissue cells cultured with or without IL-12 was determined. In addition, T cells were obtained 14 days after culturing RA synovial tissue cells with IL-2 alone or with IL-2 plus IL-12, neutralizing anti-IL-12, or IL-4, and cytokine patterns (i.e., IFNgamma and IL-4 levels) were determined by stimulating cells for 24 hours with anti-CD3 plus phorbol myristate acetate. RESULTS: Synovial tissues from RA patients more strongly expressed IL-12 p40 mRNA than did OA tissues. Dissociated tissue cells from 21 of 37 RA patients spontaneously released detectable amounts of IL-12 p70 (> or = 12.5 pg/ml) in culture, whereas production of IL-12 by OA tissues was limited. By immunohistochemical analysis, IL-12-producing cells were localized mainly in the sublining layer of RA synovium, and mostly expressed the CD68 antigen. Levels of IFNgamma production by RA synovial tissue cells were potently and selectively enhanced by IL-12. The ability of IL-2-expanding synovial T cells to produce IFNgamma was augmented by costimulation with IL-12 and diminished by anti-IL-12, while it was not affected by IL-4. CONCLUSION: These data suggest that IL-12, produced mainly by macrophage-lineage cells, may be involved in IFNgamma-dominant cytokine production by infiltrating T cells in joints with chronic RA.

Arthritis, Rheumatoid↗
PubMed1998

Cytotoxic T lymphocytes in resistance to tuberculosis.

Recent experimental evidence has suggested T cells recognizing antigens in the context of both classical MHC class I and nonclassical class I-like molecules contribute to protective responses against Mycobacterium tuberculosis (MTB) infection. Our aims were to characterize both types of T cells, and to explore the basis of communication between the tubercle bacilli and the MHC class I pathway of the host macrophage. A model system was developed using exogenously added ovalbumin as a surrogate antigen to study presentation by MTB-infected macrophages. Viable, virulent MTB and closely related mycobacterial species facilitated the presentation of ovalbumin on MHC class I molecules to CD8+ cytolytic T cells that was dependent upon the cytosolic transport of peptides, implying communication between the MTB phagosome and the host cell cytoplasm. MHC class I presentation of soluble antigens was mimicked by Listeria monocytogenes, which grows within the host cell cytoplasm, as well as its purified hemolysin. We have also characterized T cells that recognize nonpeptide MTB antigens presented by CD1 molecules. CD1-restricted T cells demonstrated to lyse macrophages infected with virulent MTB were divided into distinct subsets based on surface phenotype (CD4-CD8- versus CD8-) and cytotoxicity mechanism (Fas receptor-mediated versus granule exocytosis). A functional consequence of these two mechanisms was observed that while both subsets lysed infected macrophages, only those T cells utilizing the granule exocytosis pathway were able to reduce viability of intracellular MTB.

Animals↗
PubMed1998

CD1-restricted T-cells influence IgG subclass and IgE production.

BACKGROUND: Human CD1 has recently emerged as a third family of antigen-presenting molecules that is distinct from either major histocompatibility complex class I or class II. OBJECTIVE: We investigated whether the CD1b-restricted T-cell interaction with antigen alters human IgG subclass and IgE isotype production. METHODS: CD1b-restricted antigen-specific T cells derived from the skin lesion of a patient with leprosy were stimulated with their cognate antigen, lipoarabinomman (LAM) of Mycobacterium leprae, in the presence of CD1+ antigen-presenting cells and tested for their ability to alter IgG subclass and IgE production from IgD+ B cells. RESULTS: CD1-restricted T cells cultured with CD1+ antigen-presenting cells in the absence of LAM induced IgG1, IgG3, IgG4, and IgE, whereas CD1b-restricted T cells cultured in the presence of LAM induced IgG1 and IgG3 and inhibited production of IgG4 and IgE. Production of IgG4 and IgE was rescued in the CD1-restricted system by the addition of anti-interferon-gamma. IgG2 production was not induced under any circumstances. CONCLUSION: In this study we demonstrated that a specific CD1b-restricted T-cell line can behave similarly to classically-restricted Th1-type T cells. CD1b-restricted T-cells of this type may regulate immune responses to microbial pathogens by simultaneously enhancing cell-mediated immunity and downregulating IgG4 and IgE responses.

Antigen-Presenting Cells↗
PubMed1998

Cytotoxic T cell responses to intracellular pathogens.

Host defense against intracellular pathogens is thought to require cytotoxic T cells. Recent studies have investigated the impact of host cell lysis and cytokine production by cytotoxic T lymphocytes on the fate of intracellular pathogens. The identification of two mechanisms of lysis induced by cytotoxic T lymphocytes--the granule exocytosis pathway and the Fas-FasL interaction--have provided new insight into the role of cytotoxic T lymphocyters in immunity to infection.

Animals↗
PubMed1998

Molecular interaction of CD1b with lipoglycan antigens.

The ability of human CD1b molecules to present nonpeptide antigens is suggested by the T cell recognition of microbial lipids and lipoglycans in the presence of CD1b-expressing antigen-presenting cells. We demonstrate the high-affinity interaction of CD1b molecules with the acyl side chains of known T cell antigens, lipoarabinomannan, phosphatidylinositol mannoside, and glucose monomycolate. Furthermore, CD1b-antigen binding was optimal at acidic pH, consistent with the known requirement for endosomal acidification in CD1b-restricted antigen presentation. The mechanism for CD1b-ligand interaction involves the partial unfolding of the alpha helices of CD1b at acidic pH, revealing a hydrophobic binding site that could accommodate lipid. These data provide direct evidence that the CD1b molecule has evolved unique biochemical properties that enable the binding of lipid-containing antigens from intracellular pathogens.

Anilino Naphthalenesulfonates↗
PubMed1998

The tyrosine-containing cytoplasmic tail of CD1b is essential for its efficient presentation of bacterial lipid antigens.

CD1b is an antigen-presenting molecule that mediates recognition of bacterial lipid and glycolipid antigens by specific T cells. We demonstrate that the nine-amino acid cytoplasmic tail of CD1b contains all of the signals required for its normal endosomal targeting, and that the single cytoplasmic tyrosine is a critical component of the targeting motif. Mutant forms of CD1b lacking the endosomal targeting motif are expressed at high levels on the cell surface but are unable to efficiently present lipid antigens acquired either exogenously or from live intracellular organisms. These results define the functional role of the CD1b targeting motif in a physiologic setting and demonstrate its importance in delivery of this antigen-presenting molecule to appropriate intracellular compartments.

Amino Acid Sequence↗
PubMed1998

CD1 presents antigens from a gram-negative bacterium, Haemophilus influenzae type B.

Human CD1 is a family of nonpolymorphic major histocompatibility complex class I-like molecules capable of presenting mycobacterial lipids, including lipoarabinomannan (LAM), to double-negative (DN; CD4(-) CD8(-)) as well as CD8(+) T cells. Structural similarities between LAM and the capsular polysaccharides of gram-negative bacteria led us to consider the latter as candidate CD1 ligands. We derived two CD1-restricted DN T-cell populations which proliferated to Haemophilus influenzae type b (Hib) antigen. One T-cell population also proliferated to proteinase K-treated Hib antigen, suggesting that it recognized a nonpeptide. Our work thus expands the universe of T cell antigens to include nonpeptides distinct from mycobacterial lipids and suggests a potential role for CD1-restricted T cells in immunity to Hib.

Antigen Presentation↗
PubMed1998

Peripheral blood mononuclear cells express mutated NCCT mRNA in Gitelman's syndrome: evidence for abnormal thiazide-sensitive NaCl cotransport.

Genetic analysis has demonstrated complete linkage between the human thiazide-sensitive sodium chloride cotransporter gene (NCCT or TSC) and Gitelman's syndrome (GS). Several genomic NCCT mutations have been reported. This study was performed to determine whether peripheral blood mononuclear cells (PBMC) express NCCT mRNA and whether defective PBMC NaCl cotransport could be demonstrated in GS. PBMC were isolated from two brothers with GS, their parents, and healthy control subjects. Northern analysis revealed that NCCT mRNA is expressed in PBMC. The sequence of full-length NCCT cDNA amplified from normal PBMC was identical to human renal NCCT cDNA. Two different mutations were detected in the patients' NCCT cDNA (compound heterozygote). In cDNA derived from the patient's maternal allele, exon 24 was deleted, resulting in a premature stop codon (after amino acid 920). cDNA derived from the patient's paternal allele had an additional 119-bp insertion between exons 3 and 4, generating a premature stop codon (after amino acid 187). The patient's genomic DNA had a previously described 5' splice site mutation in intron 24, GGT --> GTT (maternal allele), and a new 3' splice site mutation in intron 3, CAG --> CAA (paternal allele), which resulted in the activation of a nearby cryptic splice site in intron 3. The latter mutation was not present in 300 normal chromosomes. To determine the functional significance of these findings, chlorothiazide-inhibitable 22Na uptake was measured in PBMC from control subjects, the parents, and the patients with GS in the presence of bumetanide. In control PBMC, chlorothiazide inhibited 22Na uptake by approximately 9%. PBMC from the two patients with GS failed to respond to chlorothiazide. These results demonstrate that PBMC can be used for mutational analysis of NCCT mRNA in patients with GS. Furthermore, functional evidence is provided that the underlying cause of GS is defective NCCT NaCl cotransport.

Adult↗
PubMed1997

Structural requirements for glycolipid antigen recognition by CD1b-restricted T cells.

The human CD1b protein presents lipid antigens to T cells, but the molecular mechanism is unknown. Identification of mycobacterial glucose monomycolate (GMM) as a CD1b-presented glycolipid allowed determination of the structural requirements for its recognition by T cells. Presentation of GMM to CD1b-restricted T cells was not affected by substantial variations in its lipid tails, but was extremely sensitive to chemical alterations in its carbohydrate or other polar substituents. These findings support the view that the recently demonstrated hydrophobic CD1 groove binds the acyl chains of lipid antigens relatively nonspecifically, thereby positioning the hydrophilic components for highly specific interactions with T cell antigen receptors.

Antigen Presentation↗
PubMed1997

Mouse CD1 is mainly expressed on hemopoietic-derived cells.

The mouse CD1 (mCD1) is a class I-like molecule that is encoded outside the MHC. Recent studies demonstrate that mCD1 presents hydrophobic peptides to CD8+ T cells and also that it is recognized by a population of NK1.1+ T cells that are thought to play an immunoregulatory role because of their ability to secrete IL-4. It has previously been reported that mCD1 is expressed predominantly by intestinal epithelial cells, although most NK1.1+ T cells are located elsewhere. We, therefore, have generated new mAbs to mCD1 to investigate its tissue distribution. The principal site of mCD1 expression in normal mice is on cells in the hemopoietic series, including constitutive expression on nearly all T and B cells, on macrophages, and on dendritic cells. Other than bone marrow-derived cells, mCD1 is not widely expressed and is not detectable on great majority of intestinal epithelial cells. The B cells, but not the T cells, from beta2m-deficient mice can be recognized by two mCD1 autoreactive T hybridomas. Therefore, although we could not detect a beta2m-independent form of mCD1 using these mAbs, mCD1 in a different conformation or a mCD1-related molecule is likely to be expressed in the absence of beta2m on some cell types. The pattern of expression of mCD1 correlates with the distribution of NK1 T cells and is consistent with an important Ag-presenting function for this molecule.

Animals↗
PubMed1997

Single-cell cytokine analysis of gamma delta T cell responses to nonpeptide mycobacterial antigens.

TCR gamma delta T cells are considered important in the rapid immune response to intracellular infection. We investigated the early response of peripheral blood gamma delta T cells to the nonpeptide Ag isopentenyl pyrophosphate and to its synthetic analogue ethyl pyrophosphate. In healthy donors, an increase in the number of gamma delta T cells was detected as soon as 4 days after stimulation with the nonpeptide Ags. Single-cell analysis of cytokine production was performed by intracellular staining of IFN-gamma and IL-4. gamma delta T cells were found to rapidly expand and produce IFN-gamma in response to nonpeptide Ags. Furthermore, IL-12 augmented the IFN-gamma response. In contrast, gamma delta T cells from the majority of HIV+ donors did not expand or express IFN-gamma in response to nonpeptide Ags, even in the presence of IL-12. These findings indicate a role for nonpeptide-reactive gamma delta T cells in effective cell-mediated immunity for intracellular pathogens.

Antigens, Bacterial↗
PubMed1997

Determinants of T cell reactivity to the Mycobacterium leprae GroES homologue.

The 10-kDa protein Ag of Mycobacterium leprae, a human GroES hsp10 cognate, is a major T cell Ag in human leprosy infection. We investigated the mechanism for T cell responsiveness to this Ag according to the trimolecular interaction between T cell, peptide, and Ag-presenting element. This research was accomplished by mapping T cell epitopes in leprosy patients and correlating these responses with peptide-MHC binding affinities. We found that the majority of tuberculoid leprosy patients responded to peptides corresponding to residues 25-39 and 28-42. Truncation analysis of these peptides mapped the exact epitope to be within the overlapping region comprising residues 28-39. Responsiveness was correlated with the HLA-DRB5*0101 allele, which bound the peptides with moderate affinity. This allele is linked to HLA-DR2, which is associated with the resistant form of leprosy. Therefore, T cell responsiveness in tuberculoid leprosy may be mediated by the ability of HLA-DRB5*0101 to bind and present peptides of the immunodominant 10-kDa Ag.

Alleles↗
PubMed1997

Differential effects of cytolytic T cell subsets on intracellular infection.

In analyzing mechanisms of protection against intracellular infections, a series of human CD1-restricted T cell lines of two distinct phenotypes were derived. Both CD4(-)CD8(-) (double-negative) T cells and CD8(+) T cells efficiently lysed macrophages infected with Mycobacterium tuberculosis. The cytotoxicity of CD4(-)CD8(-) T cells was mediated by Fas-FasL interaction and had no effect on the viability of the mycobacteria. The CD8(+) T cells lysed infected macrophages by a Fas-independent, granule-dependent mechanism that resulted in killing of bacteria. These data indicate that two phenotypically distinct subsets of human cytolytic T lymphocytes use different mechanisms to kill infected cells and contribute in different ways to host defense against intracellular infection.

Antigens, CD1↗
PubMed1997

Interferon-gamma differentially regulates interleukin-12 and interleukin-10 production in leprosy.

The ability of monocytes to influence the nature of the T cell response to microbial pathogens is mediated in part by the release of cytokines. Of particular importance is the release of IL-12 and IL-10 by cells of the monocyte/macrophage lineage upon encountering the infectious agent. IL-12 promotes cell mediated immunity (CMI) to intracellular pathogens by augmenting T-helper type 1 responses, whereas IL-10 downregulates these responses. The ability of IFN-gamma to modulate the balance between IL-12 and IL-10 production was examined by studying leprosy as a model. In response to Mycobacterium leprae stimulation, IFN-gamma differentially regulated IL-12 and IL-10 production resulting in upregulation of IL-12 release and downregulation of IL-10 release. Furthermore, we determined that the mechanism by which IFN-gamma downregulates IL-10 was through the induction of IL-12. The data suggest a model of lymphocyte-monocyte interaction whereby the relative presence or absence of IFN-gamma in the local microenvironment is a key determinant of the type of monocyte cytokine response, and hence the degree of CMI in the host response to infection.

Down-Regulation↗