DICTIONARY

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1. Endogenous (cytosolic) pathway:  the pathway involved in waste products from self-cells and Ag-recognition on the MHC Class I. Peptides that are broken down by proteolysis, and are transported from the cytosol to the rough ER (where catabolized peptides go to, to meet up with MHC I & TAP is), to the Golgi (where proteins are modified), and then the vesicles (where proteins are kept). When proteosome cuts off the protein, it diffuses into the cells by tapasin. Now, proteins arrive on MHC class I molecules.

2. ITAM: Immunoreceptor tyrosine-based activator motif sequences amino acid in the cytoplasmic tail (that contains serine) and repeats itself more than once. 

3. Invariant chain: non-MHC encoded protein interacts with the class II peptide-binding groove preventing any endogenously derived peptides from binding while the class II molecule is withing the RER. 

4. Double-negative (DN) cells: these are fetal T cells that lack both CD4 & CD8 cells. 

Reference

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