Urea transporters UT-A1 and UT-A3 facilitate diffusion of urea out of the medullary collecting ducts while UT-A2 facilitates urea diffusion into the thin descending loop of Henle.

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#Id: 7208

#Unit 5. Developmental Biology

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

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#Id: 7209

#Unit 5. Developmental Biology

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

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#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.

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#Id: 7211

#Unit 5. Developmental Biology

Cross-presentation

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#Id: 7212

#Unit 5. Developmental Biology

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

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#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