Some people have an allele called Δ32 at the CCR5 locus in which 32 bp are deleted.

CCR5 that plays a role in inflammatory response. Unfortunately, this protein is also a key to human immunodeficiency virus (HIV) infection. The virus binds to a loop of the CCR5 protein and then enters the cell.

The missing part of the gene codes for the loop in the protein to which the virus attaches. 

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#Unit 4. Cell Communication and Cell Signaling

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

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#Unit 4. Cell Communication and Cell Signaling

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

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#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.

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#Unit 4. Cell Communication and Cell Signaling

Cross-presentation

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#Unit 4. Cell Communication and Cell Signaling

Codominant Expression

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#Unit 4. Cell Communication and Cell Signaling