Biomedical subjects

Marcin P Mycko

Publications and source records attributed to Marcin P Mycko.

10 recordsLinked to original sources

PubMed2006

Linkage disequilibrium screening for multiple sclerosis implicates JAG1 and POU2AF1 as susceptibility genes in Europeans.

By combining all the data available from the Genetic Analysis of Multiple sclerosis in EuropeanS (GAMES) project, we have been able to identify 17 microsatellite markers showing consistent evidence for apparent association. As might be expected five of these markers map within the Major Histocompatibility Complex (MHC) and are in LD with HLA-DRB1. Individual genotyping of the 12 non-MHC markers confirmed association for three of them--D11S1986, D19S552 and D20S894. Association mapping across the candidate genes implicated by these markers in 937 UK trio families revealed modestly associated haplotypes in JAG1 (p=0.019) on chromosome 20p12.2 and POU2AF1 (p=0.003) on chromosome 11q23.1.

Calcium-Binding Proteins↗

PubMed2006

Cutting edge: influence of the TCR Vbeta domain on the selection of semi-invariant NKT cells by endogenous ligands.

Invariant Valpha14 (Valpha14i) NKT cells are a murine CD1d-dependent regulatory T cell subset characterized by a Valpha14-Jalpha18 rearrangement and expression of mostly Vbeta8.2 and Vbeta7. Whereas the TCR Vbeta domain influences the binding avidity of the Valpha14i TCR for CD1d-alpha-galactosylceramide complexes, with Vbeta8.2 conferring higher avidity binding than Vbeta7, a possible impact of the TCR Vbeta domain on Valpha14i NKT cell selection by endogenous ligands has not been studied. In this study, we show that thymic selection of Vbeta7(+), but not Vbeta8.2(+), Valpha14i NKT cells is favored in situations where endogenous ligand concentration or TCRalpha-chain avidity are suboptimal. Furthermore, thymic Vbeta7(+) Valpha14i NKT cells were preferentially selected in vitro in response to CD1d-dependent presentation of endogenous ligands or exogenously added self ligand isoglobotrihexosylceramide. Collectively, our data demonstrate that the TCR Vbeta domain influences the selection of Valpha14i NKT cells by endogenous ligands, presumably because Vbeta7 confers higher avidity binding.

Animals↗

PubMed2004

Modified amino acid copolymers suppress myelin basic protein 85-99-induced encephalomyelitis in humanized mice through different effects on T cells.

A humanized mouse bearing the HLA-DR2 (DRA/DRB1*1501) protein associated with multiple sclerosis (MS) and the myelin basic protein (MBP) 85-99-specific HLA-DR2-restricted T cell receptor from an MS patient has been used to examine the effectiveness of modified amino acid copolymers poly(F,Y,A,K)n and poly-(V,W,A,K)n in therapy of MBP 85-99-induced experimental autoimmune encephalomyelitis (EAE) in comparison to Copolymer 1 [Copaxone, poly(Y,E,A,K)n]. The copolymers were designed to optimize binding to HLA-DR2. Vaccination, prevention, and treatment of MBP-induced EAE in the humanized mice with copolymers FYAK and VWAK ameliorated EAE more effectively than Copolymer 1, reduced the number of pathological lesions, and prevented the up-regulation of human HLA-DR on CNS microglia. Moreover, VWAK inhibited MBP 85-99-specific T cell proliferation more efficiently than either FYAK or Copolymer 1 and induced anergy of HLA-DR2-restricted transgenic T cells as its principle mechanism. In contrast, FYAK induced proliferation and a pronounced production of the antiinflammatory T helper 2 cytokines IL-4 and IL-10 from nontransgenic T cells as its principle mechanism of immunosuppression. Thus, copolymers generated by using different amino acids inhibited disease using different mechanisms to regulate T cell responses.

Amino Acid Sequence↗

PubMed2004

Cross-reactive TCR responses to self antigens presented by different MHC class II molecules.

Autoreactive T cells represent a natural repertoire of T cells in both diseased patients and healthy individuals. The mechanisms regulating the function of these autoreactive T cells are still unknown. Ob1A12 is a myelin basic protein (MBP)-reactive Th cell clone derived from a patient with relapsing-remitting multiple sclerosis. Mice transgenic for this human TCR and DRA and DRB1*1501 chains develop spontaneous experimental autoimmune encephalomyelitis. The reactivity of Ob1A12 is reported to be restricted to recognition of MBP peptide 85-99 in the context of DRB1*1501. DRA/DRB1*1501 and the patient's other restriction element, DRA/DRB1*0401, differ significantly in their amino acid sequences. In this study we describe an altered peptide ligand derived from MBP(85-99) with a single amino acid substitution at position 88 (Val to Lys; 88V-->K), that could stimulate the Ob1A12.TCR in the context of both DRA/DRB1*1501 and DRA/DRB1*0401. Analysis of a panel of transfected T cell hybridomas expressing Ob1A12.TCR and CD4 indicated that Ob1A12.TCR cross-reactivity in the context of DRA/DRB1*0401 is critically dependent on the presence of the CD4 coreceptor. Furthermore, we found that activation of Ob1A12.TCR with MBP altered peptide ligand 85-99 88V-->K presented by DRB1*1501 or DRB1*0401 resulted in significant differences in TCR zeta phosphorylation. Our data indicate that injection of altered peptide ligand into patients heterozygous for MHC class II molecules may result in unexpected cross-reactivities, leading to activation of autoreactive T cells.

Amino Acid Sequence↗

PubMed2004

Gammadelta T cells enhance the expression of experimental autoimmune encephalomyelitis by promoting antigen presentation and IL-12 production.

Using an adoptive transfer model of experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein (MBP)-reactive lymph node cells (LNC), we have shown that depletion of gammadelta T cells from LNC resulted in diminished severity of EAE in recipient mice, both clinically and histopathologically. The reduced potency of gammadelta T cell-depleted LNC to induce EAE correlated with decreased cell proliferation in response to MBP. The gammadelta T cell effect upon the threshold of MBP-induced LNC proliferation and EAE transfer was restored by reconstitution of gammadelta T cells derived from either MBP-immunized or naive mice, indicating that this effect was not Ag specific. The enhancing effect of gammadelta T cells on MBP-induced proliferation and EAE transfer required direct cell-to-cell contact with LNC. The gammadelta T cell effect upon the LNC response to MBP did not involve a change in expression of the costimulatory molecules CD28, CD40L, and CTLA-4 on TCRalphabeta(+) cells, and CD40, CD80, and CD86 on CD19(+) and CD11b(+) cells. However, depletion of gammadelta T cells resulted in significant reduction in IL-12 production by LNC. That gammadelta T cells enhanced the MBP response and severity of adoptive EAE by stimulating IL-12 production was supported by experiments showing that reconstitution of the gammadelta T cell population restored IL-12 production, and that gammadelta T cell depletion-induced effects were reversed by the addition of IL-12. These results suggest a role for gammadelta T cells in the early effector phase of the immune response in EAE.

Animals↗

PubMed2004

Inducible heat shock protein 70 promotes myelin autoantigen presentation by the HLA class II.

In this study, we investigated the role of the inducible form of heat shock protein 70 (hsp70) in the presentation of the major putative autoantigen in multiple sclerosis, myelin basic protein (MBP), in the context of appropriate MHC class II. By coimmunoprecipitation, we found that MBP is associated with hsp70 in APC in an ATP/ADP-dependent manner. Additionally, using confocal microscopy, hsp70 was detected in the endocytic pathway of APC, where it colocalized with MBP and HLA-DR. The immunodominant epitopes of MBP 85-99 and 80-99 were shown to bind selectively and specifically to hsp70 by surface plasmon resonance. The functional significance of MBP interaction with hsp70 was demonstrated by the detection of enhanced responses of an MBP-specific T cell hybridoma to MBP and MBP 80-99 with increasing levels of hsp70 and reduced responses when hsp70 expression was diminished within APC-expressing DRA*0101, DRB1*1501 (DR1501). However, when MBP 85-99 was used as the stimulus, T cell hybridoma responses were not enhanced by hsp70 overexpression within APC, suggesting that hsp70 contributes to Ag processing rather than Ag presentation. The importance of a direct association between MBP and hsp70 in the presentation pathways was demonstrated by enhanced efficacy of MBP presentation by APC transfected with a plasmid vector encoding a fusion hsp70-MBP protein. This is the first report on the involvement of self-inducible hsp70 in MHC class II-dependent autoantigen processing by APC. It implicates that aberrant self hsp expression may lead to the enhancement/modulation of autoimmune responses.

Amino Acid Sequence↗

PubMed2004

Microarray gene expression profiling of chronic active and inactive lesions in multiple sclerosis.

Multiple sclerosis, a primary autoimmune disease of the central nervous system has been characterized by the presence of the demyelinating lesions (plaques) in the CNS. To further understand the gene transcription status of the two most common lesions, chronic active and chronic inactive, we have performed a cDNA microarray analysis of these two lesion type. Comparative analysis of differential gene expression of chronic active and inactive lesions have confirmed the existence of a significant difference in the transcriptional profiles of these two lesion types in both marginal and central areas. Different sets of genes were highlighted, including genes of inflammatory characteristics, apoptosis related and stress-induced, indicating their potential role in MS pathogenesis.

Brain↗

PubMed2003

A whole genome screen for association in Polish multiple sclerosis patients.

We have performed the first systematic search for MS susceptibility genes completed in the Polish population. This screen was performed using 6000 microsatellite markers typed in pooled DNA from cases (n=200), controls (n=200) and trio families (n=129). Five associated markers are identified, one (D6S2444) from the HLA region and four are from novel regions not previously associated with MS, 2p16 (D2S2153), 3p13 (D3S3568), 7p22 (D7S2521) and 15q26 (D15S649).

Adult↗

PubMed2003

cDNA microarray analysis in multiple sclerosis lesions: detection of genes associated with disease activity.

cDNA microarray analysis of the regions of pathologically proven different activity of multiple sclerosis lesions was performed. Major differences in gene expression (DGE) occurred between the lesion margin and lesion centre in active lesions studied (57 and 69 genes differentially expressed, respectively), whereas the margins and centres of silent lesions showed markedly reduced heterogeneity (only 11 and two genes differentially expressed, respectively). To compare differences between chronic active and silent lesions, we performed DGE comparison of the pooled data from both types of lesions. The major DGE occurred at the lesion margin, 156 (26; 5%), the greater number representing upregulated genes at the margin of active lesions (15%). Fourteen genes were found to be significantly upregulated in marginal versus central zones in active lesions examined. These genes comprised predominantly inflammation/immune-related factors. We also performed DGE analysis of pooled genes upregulated at the margin of active lesions and found that among the 50 genes showing differences, nine out of 14 were identified in the previous analysis of overlapping differentially expressed genes. Thus this microarray analysis has identified a novel set of genes associated with lesion activity in multiple sclerosis, many of them not previously linked with the disease.

Brain↗

PubMed2003

Heat shock protein 70 associations with myelin basic protein and proteolipid protein in multiple sclerosis brains.

Heat shock proteins (hsp) are known to facilitate the generation of specific immune responses by chaperoning proteins and peptides involved in T cell activation. Hsp have been shown to be strikingly elevated in multiple sclerosis (MS) lesions. The unique chaperonin properties of hsp70 have allowed identification of immunogenic proteins bound to it by the ex vivo demonstration of hsp associations with proteins implicated in the immune response. We have investigated the association of hsp70 with myelin basic protein (MBP), myelin proteolipid protein (PLP) and myelin oligodendrocyte protein (MOG) in MS and control brain tissue. In co-immunoprecipitation experiments, in all samples of MS brains examined (n = 3), but not control brain tissue (n = 3), direct association of MBP with hsp70, but not with hsp90, was found. In some MS brain samples, association between PLP and hsp70 was also seen. In similar co-immunoprecipitation experiments on brain tissue obtained from mice with experimental autoimmune encephalomyelitis (n = 5) induced by immunization with PLP peptide, specific association of hsp70 with PLP and MBP was found. Using surface plasmon resonance we demonstrated specific binding of hsp70 with MBP in vitro. Analysis of the amounts of MBP bound to hsp70 yielded a molecular ratio of MBP binding to hsp70 at 6.5:1. MBP complexed with hsp70 was taken up at significantly higher rates by antigen-presenting cells than MBP alone and enhanced MBP-specific immune responses. These results indicate that hsp70 specifically associates with MBP in MS brain tissue. This association might be relevant to the enhanced immune recognition of MBP in MS.

Antigen-Presenting Cells↗