Chromosome duplications are one way in which new genes evolve.

#Id: 7210

#Unit 5. Developmental Biology

Class II MHC transcriptional activator called CIITA and another transcription factor called RFX, have both been shown to activate the promoter of class II MHC genes. Defects in these transcription factors cause one form of bare lymphocyte syndrome.

#Id: 7211

#Unit 5. Developmental Biology

Cross-presentation

#Id: 7212

#Unit 5. Developmental Biology

Presentation of nonpeptide antigens derived from pathogens involves the nonclassical class I–like CD1 molecule

#Id: 7213

#Unit 5. Developmental Biology

Class I presentation requires internal synthesis of virus protein, as shown by the requirement that the target cell be infected by live virus, and by the inhibition of class I presentation observed when protein synthesis was blocked by the inhibitor emetine

#Id: 7214

#Unit 5. Developmental Biology

Class II presentation can occur with either live or replication-incompetent virus; protein synthesis inhibitors had no effect, indicating that new protein synthesis is not a necessary condition of class II presentation.

#Id: 7215

#Unit 5. Developmental Biology

Class II, but not class I, presentation is inhibited by treatment of the cells with an agent that blocks endocytic processing within the cell (chloroquine).