Dendritic Cells from Mice Lacking the Invariant Chain Express High Levels of Membrane MHC Class II Molecules in Vivo
We investigated in H-2k mice bearing a genetically disrupted invariant chain (Ii) gene1, the MHC class II expression and antigen presentation ability of dendritic cells (DC) freshly purified from the spleen (SpDC) or derived from bone marrow precursors (BMDC) upon treatment with GM-CSF. In the absence of Ii, class II α/β heterodimers are expressed on the DC membranes to a similar extent than in control mice, in contrast to splenic B cells. Class I1 molecules immunoprecipitated from the plasma membrane of li deficient DC are compact indicating that the dimers are stabilized by antigenic peptides2. Furthermore DC from li mutant mice are able to present to CD4+ T lymphocytes, epitopes derived from the processing of the hen egg lysozyme (HEL) that normally require expression of the Ii molecule for presentation by B cells. All together, our results show that the antigen processing machinary of DC provides peptides that can reach class li molecules and stabilize their conformation in the absence of Ii mediated targeting of class II complexes.
KeywordsDendritic Cell Invariant Chain Bone Marrow Precursor Antigen Presentation Ability Express High Level
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