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. 2008 Apr 22;105(16):6121-6.
doi: 10.1073/pnas.0801973105. Epub 2008 Apr 21.

Dendritic Cells in Islets of Langerhans Constitutively Present Beta Cell-Derived Peptides Bound to Their Class II MHC Molecules

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Free PMC article

Dendritic Cells in Islets of Langerhans Constitutively Present Beta Cell-Derived Peptides Bound to Their Class II MHC Molecules

Boris Calderon et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

Islets of Langerhans from normal mice contained dendritic cells (DCs) in the range of 8-10 per islet. DCs were found in several mouse strains, including those from lymphocyte-deficient mice. DCs were absent in islets from colony stimulating factor-1 deficient mice and this absence correlated with small size islets. Most DCs were found next to blood vessels and resided in islets for several days. Some DCs contained insulin-like granules, and most expressed peptide-MHC complexes derived from beta cell proteins. Islet DCs were highly effective in presenting beta cell antigens to CD4 T cells ex vivo. Presentation of beta cell-derived peptide-MHC complexes by DCs neither depended on islet inflammation nor correlated with the extent of spontaneous beta cell death. Periislet stroma DCs did not contain beta cell peptide-MHC complexes; however, 50% of DCs in pancreatic node were positive. Hence, presentation of high levels of beta cell antigens normally takes place by islet DCs, a finding that has to be placed in the perspective of autoimmune diabetes.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Distribution and phenotype of intraislet DCs. (a) (Left) Percentage of CD11c+ cells in islets of 8-week-old NOD.rag-1−/− mice. (Right) Distribution of islet area vs. CD11c+ cells per islet. In all graphs, each dot represents one isolated islet. (b and c) Phenotype of intraislets DCs in 8-week-old B10.BR (b) and NOD.rag-1−/− (c) mice.
Fig. 2.
Fig. 2.
Immunofluorescence and 2 photon analysis of islet DCs. (a) Islet of an 8-week-old B6.CD11c-YFP mouse showing YFP+ DCs (green). (b) Same islet stained for class II (I–Ab in red). (c) Islet stained for CD11c (green) and PECAM-1 (red). (d) Three-dimensional structure analysis by 2P imaging showing an islet with CD11c-YFP (green) cells and vessels (PECAM-1) in red. (Inset) Micrograph showing the contact of DCs with the vessel. (e) Islets from IP-HEL and B10.BR mice stained for CD11c (green) and for 48–61–I–Ak complex (red). Note the positive staining of the islet CD11c+ cells for the 48–61–I–Ak complex in the IP-HEL islet, whereas the CD11c+ cells in the control B10.BR islets were negative.
Fig. 3.
Fig. 3.
Electron microscopy analysis of NOD.rag-1−/− islets. (a) Islet DCs (black arrow) next to blood vessels (white arrows). (b) Higher magnification of islet DCs showing close interaction between its dendrites and the endothelial wall of the vessel (arrows). (c) Islet DCs (arrow) with a long dendrite extending parallel to an endothelial vessel wall. Note circulating leukocyte with a cytoplasmic projection next to the fenestrae of the endothelium. (d) Higher magnification of dendrite close to the vessel wall from the boxed area in c. Shown is the DC dendrite (black arrow) with a clathrin-coated vesicle facing an endothelial cell fenestrae (white arrow). (e) Islet DC with an insulin like-granule granule inside a vacuole (arrow). (f) Another example with several insulin-like granules inside vacuoles (arrows).
Fig. 4.
Fig. 4.
Islet DCs under steady state and inflammation. (a) NOD.rag-1−/− mice (8 weeks old) received a sublethal dose of 650R, islets were isolated at different times and stained for class II MHC. Note the decreased number of intraislet DCs starting at 72h and at day 7 after irradiation in comparison with unirradiated mice. (b) NOD.rag-1−/− mice were treated with low dose STZ plus sublethal irradiation (Left) or STZ alone (Right). Isolated islets at different time points were stained for class II and counted total number of DCs per islet.
Fig. 5.
Fig. 5.
Pancreatic (PLN) and brachial lymph node (BLN) analysis for the presence of HEL peptide–MHC complexes in DCs. Lymph Nodes from B10.BR, ML-5 (serum HEL), IP-HEL, and mHEL were gated on CD11c and analyzed for the presence of HEL peptide–MHC complexes. Only PLN from IP-HEL and mHEL mice contained DCs positive for the HEL peptide–MHC complex. *, Histogram from splenocyte analysis of mHEL mice.
Fig. 6.
Fig. 6.
Dispersed islet T cell assays. (a) BDC2.5 T cell hybridomas were cultured with titrating amounts of dispersed islet cells from NOD.rag-1−/− mice. (b) Insulin-specific T cell hybridomas cultured with NOD.rag-1−/− dispersed islets. (c) 3A9 T cell hybridomas cultured with dispersed islets from high producer IP-HEL mice (ILK3 strain). (d) 3A9 T cell hybridomas cultured with dispersed islets from low producer IP-HEL mice (117 strain) with or without low dose STZ treatment 4 days before islet isolation. LB11 T cell hybridomas (against the HEL minor epitope 20–35-I-Ak) were also activated when cultured with 105 IP-HEL dispersed islets with or without STZ (20,000 and 24,000 cpm, respectively).

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