Pathways of Processing of Insulin by Antigen‐Presenting Cells

Delovitch, Terry L.; Semple, John W.; Naquet, Philippe; Bernard, Nicole F.; Elllis, Janet; Champagne, P; Phillips, M. L.

doi:10.1111/j.1600-065x.1988.tb00780.x

Cited by 19 publications

(13 citation statements)

References 92 publications

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“…The insulin-derived peptide A1-A14/B1-B16 is more immunogenic than insulin itself. This peptide (A1-A14/B7-B15) is referred to as the minimal T cell epitope necessary to stimulate an insulin-reactive human T cell clone with an important recognition site containing glutamic acid (E) at position A4 [82,83]. Lang et al demonstrated using fixed BLC that porcine insulin (PI)-derived intermediates do not activate T cells, demonstrating that intermediates have to be further digested to result in a T cell epitope [84].…”

Section: Processing Of (Pro)-insulin By Cathepsinsmentioning

confidence: 99%

Processing and presentation of (pro)‐insulin in the MHC class II pathway: the generation of antigen‐based immunomodulators in the context of type 1 diabetes mellitus

Burster

Boehm

2010

Diabetes Metabolism Res

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SummaryBoth CD4 + and CD8 + T lymphocytes play a crucial role in the autoimmune process leading to T1D. Dendritic cells take up foreign antigens and autoantigens; within their endocytic compartments, proteases degrade exogenous antigens for subsequent presentation to CD4 + T cells via MHC class II molecules. A detailed understanding of autoantigen processing and the identification of autoantigenic T cell epitopes are crucial for the development of antigen-based specific immunomodulators. APL are peptide analogues of auto-immunodominant T cell epitopes that bind to MHC class II molecules and can mediate T cell activation. However, APL can be rapidly degraded by proteases occurring in the extracellular space and inside cells, substantially weakening their efficiency. By contrast, protease-resistant APL function as specific immunomodulators and can be used at low doses to examine the functional plasticity of T cells and to potentially interfere with autoimmune responses. Here, we review the latest achievements in (pro)-insulin processing in the MHC class II pathway and the generation of APL to mitigate autoreactive T cells and to activate Treg cells.

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Section: Processing Of (Pro)-insulin By Cathepsinsmentioning

confidence: 99%

Processing and presentation of (pro)‐insulin in the MHC class II pathway: the generation of antigen‐based immunomodulators in the context of type 1 diabetes mellitus

Burster

Boehm

2010

Diabetes Metabolism Res

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“…We previously demonstrated that heterodimeric disulfidelinked insulin peptides are presented by B cells to CD4+ T cells in vitro (4)(5)(6). Since this suggested that a disulfide-linked peptide binds to MHC class II, we analyzed whether human insulin (HI) is processed into a disulfide-linked peptide that binds to MHC class II in vivo.…”

mentioning

confidence: 99%

Naturally processed heterodimeric disulfide-linked insulin peptides bind to major histocompatibility class II molecules on thymic epithelial cells.

Forquet

Hadžija

Semple

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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We determined whether disulfide-linked insulin peptides that are immunogenic in vitro for CD4+ T cells bind to major histocompatibility complex class II in vivo.Radiolabeled recombinant human insulin (rHI) was injected into BALB/c mice, and processed rHI peptides bound to I-Ad molecules on different thymic antigen-presenting cells were characterized. The A6-All/B7-B19 and A19-A21/B14-B21 disufide-linked I-Ad-bound MATERIALS AND METHODS Recombinant HI (rHI) purified from Escherichia coli K-12 strain CA7233 transformed with plasmid plac 9/4 PI (Fig. 1A) was radiolabeled (-3 mCi/mmol; 1 Ci = 37 GBq) at 19 distinct amino acids (Fig. 1B) (8). Labeled rHI was indistinguishable from commercially available HI (8) and was injected into 4-to 6-week-old female BALB/c (H-2d) mice.Cortical epithelial cells (thymic nurse cells; TNCs), corticomedullary DC rosettes (T-ROS), and a separate MHC class III medullary DC/macrophage (MO) population were isolated (9). The DC/M4 population was recovered as lowdensity cells (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Remaining tissue fragments were digested with collagenase type XI (0.5 mg/ml, from Clostridium histolytum; Sigma) to obtain T-ROS and with 0.02% trypsin (0.5 ml per thymus; Sigma) in Hanks' balanced salt solution (HBSS) containing DNase I (8 pug/ml; Sigma) to purify TNCs. Before assay, TNCs were allowed to reexpress surface MHC class II during culture (16 hr, 370C) in RPMI 1640 (GIBCO) containing 10 mM Hepes (pH 7.4), 2 mM L-glutamine, 50 AuM 2-mercaptoethanol, penicillin (100 units/ ml), streptomycin (100 pg/ml), and 5% (vol/vol) fetal calf serum (CRPMI) and supplemented with interleukin 2 (IL-2; 15 units/ml).APC yields (per mouse) were 4.2 x 104 for DCs/Mos, 1.4x 105 for T-ROS, and 3.5 x 104 for TNCs. Enrichment of APCs was assessed by immunofluorescence using the anti-I-Ad MK-D6 (10), J1lD and 33D1 (both detect thymic DCs) (11), anti-CD4 GK 1.5 (12), or anti-CD8 53-6.62 (13) monoclonal antibodies. The relative I-Ad surface densities were TNCs > T-ROS > DCs/Mos, with the density on TNCs being :2-fold greater than that of DCs/M4s. APCs represented =60%o of each preparation, and their relative purity was 85-90%, as reported (14).Noncovalently linked membrane-associated peptides were acid eluted (15 min, 4°C; HBSS at pH 3.6) from thymic APCs and resolved by reversed-phase C18 HPLC (15). Intracellular peptides were extracted from the acid-treated cell pellet, passed through Sephadex G-50 to obtain "insulin-sized peaks," and analyzed by C18 HPLC (15 Pharmacia). After cell lysis and washing of the Sepharose beads in PBS containing 0.2% digitonin, immune complexes were dissociated with 8 M urea (pH 4.0) and passed through Sephadex G-25 to fractionate "insulin-sized" peaks. Labeled

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“…We previously showed that PI is internalized by pinocytosis and recycled to the surface membrane of a TA3 B-cell APC (31,32). During recycling, PI is enzymatically processed, enabling it to bind to I-A d class II molecules and to be presented to PI/I-A d -specific T-cells (23).…”

Section: Pi Is Processed Into a T-cell Epitope At Ph 55 In The Presementioning

confidence: 97%

“…To test whether 1) class II can bind a partially processed PI peptide and direct the further processing of the bound peptide into a T-cell epitope and 2) the binding of a partially processed PI peptide to class II is essential for its further processing into a T-cell epitope, we analyzed the requirements for the conversion of the partially processed PI peptide Al-A14/B1-B16 into a T-cell epitope. This PI peptide was selected for analysis, since it binds to I-A d and is presented to PI/I-A d -specific T-cells by unfixed but not fixed APCs, indicating that it needs further processing to activate T-cells (23,31). A TA3 lysate was used to process this peptide either before or after its incubation with I-A d -positive APCs, and the ability of the processed peptide to stimulate T-cell activation was then assayed.…”

Section: Pi Is Processed Into a T-cell Epitope At Ph 55 In The Presementioning

confidence: 99%

Major Histocompatibility Complex Class II Molecules Function as a Template for the Processing of a Partially Processed Insulin Peptide into a T-cell Epitope

et al. 1996

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Our understanding of how an autoantigen is processed and presented during the development of a major histocompatibility complex (MHC) class II-dependent and T-cell-mediated autoimmune disease, such as IDDM, is incompletely understood. We have used insulin as a model autoantigen in IDDM to address the question of whether MHC class II molecules play a role in the generation and/or preservation of an autoantigen peptide that stimulates T-cell activation. Analyses of the requirement of I-Ad class II molecules in the processing of the partially processed porcine insulin peptide A1-A14/B1-B16 demonstrate that the binding of this peptide to I-Ad is essential for it to be further processed and tailored into a T-cell epitope. Based on our observations, we propose a two-step model for insulin processing in which insulin is first processed by an enzyme(s) into an intermediate peptide that binds to class II and then class II functions as a template to guide the processing of this partially processed peptide by cathepsin D into a T-cell epitope. Our data further underscore the important realization that MHC class II-directed processing of an autoantigen (e.g., insulin) may regulate 1) the relative immunodominance of T-cell determinants in an autoantigen, 2) the self-reactivity to cryptic T-cell epitopes in autoantigens, and 3) the susceptibility to autoimmune disease.

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Pathways of Processing of Insulin by Antigen‐Presenting Cells

Cited by 19 publications

References 92 publications

Processing and presentation of (pro)‐insulin in the MHC class II pathway: the generation of antigen‐based immunomodulators in the context of type 1 diabetes mellitus

Processing and presentation of (pro)‐insulin in the MHC class II pathway: the generation of antigen‐based immunomodulators in the context of type 1 diabetes mellitus

Naturally processed heterodimeric disulfide-linked insulin peptides bind to major histocompatibility class II molecules on thymic epithelial cells.

Major Histocompatibility Complex Class II Molecules Function as a Template for the Processing of a Partially Processed Insulin Peptide into a T-cell Epitope

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