Mouse Anti Human Chromogranin A (paRathyroid secretory protein 1) Hybridoma [DQUD-DIHB-2]

Chromogranin A (ChgA) is an antigenic target of pathogenic CD4(+) T cells in a non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). Vasostatin-1 is a naturally processed fragment of ChgA. We have now identified a novel H2-K-d-restricted epitope of vasostatin-1, ChgA 36-44, which elicits CD8(+) T cell responses in NOD mice. By using ChgA 36-44/K-d tetramers we have determined the frequency of vasostatin-1-specific CD8(+) T cells in pancreatic islets and draining lymph nodes of NOD mice. We also demonstrate that vasostatin-1-specific CD4(+) and CD8(+) T cells constitute a significant fraction of islet-infiltrating T cells in diabetic NOD mice. Adoptive transfer of T cells from ChgA 36-44 peptide-primed NOD mice into NOD/severe combined immunodeficiency (SCID) mice led to T1D development. These findings indicate that vasostatin-1-specific CD8(+) T cells contribute to the pathogenesis of type 1 diabetes in NOD mice.

Multiple studies highlighted the overtly self-reactive T cell repertoire in the diabetes-prone NOD mouse. This autoreactivity has primarily been linked to defects in apoptosis induction during central tolerance. Previous studies suggested that thymus-specific serine protease (TSSP), a putative serine protease expressed by cortical thymic epithelial cells and thymic dendritic cells, may edit the repertoire of self-peptides presented by MHC class II molecules and shapes the self-reactive CD4 T cell repertoire. To gain further insight into the role of TSSP in the selection of self-reactive CD4 T cells by endogenous self-Ags, we examined the development of thymocytes expressing distinct diabetogenic TCRs sharing common specificity in a thymic environment lacking TSSP. Using mixed bone marrow chimeras, we evaluated the effect of TSSP deficiency confined to different thymic stromal cells on the differentiation of thymocytes expressing the chromogranin A reactive BDC-2.5 and BDC-10.1 TCRs or the islet amyloid polypeptide reactive TCR BDC-6.9 and BDC-5.2.9. We found that TSSP deficiency resulted in deficient positive selection and induced deletion of the BDC-6.9 and BDC-10.1 TCRs, but it did not affect the differentiation of the BDC-2.5 and BDC-5.2.9 TCRs. Hence, TSSP has a subtle role in the generation of self-peptide ligands directing diabetogenic CD4 T cell development. These results provide additional evidence for TSSP activity as a novel mechanism promoting autoreactive CD4 T cell development/accumulation in the NOD mouse.