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Wikipedia says that: "The antigens presented by MHC class II are derived from extracellular proteins (not cytosolic as in MHC class I)."

So does this mean that MHC class I cannot be used for peptides derived from phagocytosis by non-professional APCs? (i.e. peptides that of extracellular origin?).

For example, when non-professional APCs that can undergo phagocytosis (Eosinophil, neutrophil, dendritic cell) engulf bacteria, will they present their antigens using MHC I although the peptides are of extracellular origin? or will they not present any MHC at all? thanks!

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when non-professional APCs that can undergo phagocytosis (Eosinophil, neutrophil, dendritic cell) engulf bacteria

Dendritic cells and probably neutrophils are professional APC, so this part of the question is a little confusing.

You're asking about cross-presentation, which is the process by which extracellular antigen can be presented to CD8 T cells on MHC class I. Cross-presentation is mainly performed by certain sub-classes of dendritic cell. A number of other cell types have been shown to be capable of it, but it's not clear how important they are in vivo.

A decent review of cross-presentation is Understanding the Biology of Antigen Cross-Presentation for the Design of Vaccines Against Cancer. A review of a related but somewhat different concept (MHC recycling) is Endocytic Recycling of MHC Class I Molecules in Non-professional Antigen Presenting and Dendritic Cells.

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