Ana Maria Barral

Islet-Specific Expression of CXCL10 Causes Spontaneous Islet Infiltration and Accelerates Diabetes Development

During inflammation, chemokines are conductors of lymphocyte trafficking. The chemokine CXCL10 is expressed early after virus infection. In a virus-induced mouse model for type 1 diabetes, CXCL10 blockade abrogated disease by interfering with trafficking of autoaggressive lymphocytes to the pancreas. We have generated transgenic rat insulin promotor (RIP)-CXCL10 mice expressing CXCL10 in the β cells of the islets of Langerhans to evaluate how bystander inflammation influences autoimmunity. RIP-CXCL10 mice have islet infiltrations by mononuclear cells and limited impairment of β cell function, but not spontaneous diabetes. RIP-CXCL10 mice crossed to RIP-nucleoprotein (NP) mice expressing the NP of the lymphocytic choriomeningitis virus in the β cells had massively accelerated type 1 diabetes after lymphocytic choriomeningitis virus infection. Mechanistically, we found a drastic increase in NP-specific, autoaggressive CD8 T cells in the pancreas after infection. In situ staining with H-2Db(NP396) tetramers revealed islet infiltration by NP-specific CD8 T cells in RIP-NP-CXCL10 mice early after infection. Our results indicate that CXCL10 expression accelerates the autoimmune process by enhancing the migration of Ag-specific lymphocytes to their target site.

No Significant CTL Cross-Priming by Dendritic Cell-Derived Exosomes during Murine Lymphocytic Choriomeningitis Virus Infection

Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture, but are also present in serum. They contain a wide array of protein ligands on their surface, which has led to the hypothesis that they might mediate intercellular communication. Indeed, data support that exosomes can transfer Ags to dendritic cells (DC), and, interestingly, that these DC can subsequently induce T cell priming or tolerance. We have investigated whether this concept can be expanded to antiviral immunity. We isolated exosomes from supernatant of cultured bone marrow-derived DC (BMDC) that were infected with lymphocytic choriomeningitis virus (LCMV) or loaded with an immunodominant LCMV peptide, and characterized them by flow cytometry upon binding to beads. We then incubated the exosome preparations with BMDC and looked at their potential to activate LCMV gp33-specific naive and memory CD8 T cells. We found that exosomes do not significantly contribute to CD8 T cell cross-priming in vitro. Additionally, exosomes derived from in vitro-infected BMDC did not exhibit significant in vivo priming activity, as evidenced by the lack of protection following exosome vaccination. Thus, DC-derived exosomes do not appear to contribute significantly to CTL priming during acute LCMV infection.

Cell–cell adherence as a selection method for the generation of anti-melanoma monoclonal antibodies

The aim of the present study was to obtain monoclonal antibodies (mAbs) recognising human melanoma-associated antigens after immunisation of BALB/c mice with a 70-150 kDa membrane fraction from melanoma tumour tissues. Screening of specific antibody- producing hybridomas was performed using a novel cell-cell adherence method with the melanoma cell line M-14. Three mAbs of IgG1 isotype were selected: Mel-1, Mel-2 and Mel-3 which recognised the immunogen by ELISA and stained several melanoma cell lines positive in immunofluorescence. The molecular weight of the antigen was studied by different methods; a 170-kDa band was identified following immunoblotting of tumour lysate and a 72-kDa band was observed following immunoaffinity purification. Cell-cell adherence appears to be a reliable procedure for the generation of mAbs against native cellular antigens.