Replication of mtDNA may be stochastic because there is no control over which particular copies are replicated, so that in any cycle some mtDNA molecules may replicate more times than others.

TLS Online TPP Program

#Id: 10382

#Unit 4. Cell Communication and Cell Signaling

Expression of class II molecules by B cells is down-regulated by IFN-¥.

TLS Online TPP Program

#Id: 10383

#Unit 4. Cell Communication and Cell Signaling

Corticosteroids and prostaglandins can also decrease expression of class II MHC molecules.

TLS Online TPP Program

#Id: 10384

#Unit 4. Cell Communication and Cell Signaling

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.

TLS Online TPP Program

#Id: 10385

#Unit 4. Cell Communication and Cell Signaling

Cross-presentation

TLS Online TPP Program

#Id: 10386

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#Id: 10387

#Unit 4. Cell Communication and Cell Signaling

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.