One form of bare lymphocyte syndrome is caused by a genetic defect in MHC class

Question

One form of bare lymphocyte syndrome is caused by a genetic defect in MHC class II transactivator (CIITA). CIITA does not directly bind to DNA. Instead CIITA functions through activation of the transcription factor RFX5, hence CIITA can be classified as a transcriptional coactivator. This genetic defect results in an inability to synthesize MHC class II molecules. The non-expression of MHC class II leads to severe immunodeficiency. To investigate this condition, you have created mice that are genetically deficient in CIITA. When studying immune responses in these CIITA- deficient mice and comparing them with genetically matched wild-type mice, you will most likely find that [complete the sentence and assess each subsequent statement (145-148) as either factually correct (= “true”) or incorrect (= “false”)]:

145. the T cells from the CIITA-deficient mice will predominantly become polarized towards a TH1 phenotype, whereas some of the T cells from wild-type mice will show
a TH1 phenotype and some will show TH2 polarization.

146. the cytolytic activity of CD8+ T cells from the CIITA mice will be reduced compared to that of wild-type mice.

147. there will be an increased incidence of autoreactive T cells in the CIITA-deficient mice due to a failure to properly negatively select developing T cells in the thymus.

148. The frequency of peripheral CD4+ T cells will be very low in the CIITA-deficient mice.

Explanation / Answer

145. True

146. False. The MHC class II genes encode heterodimeric glucporteins that present antigens to CD4+T cells to initiate immune response

147. False. The MHC class II genes are expressed on the surface of activated T cells along with B cells, densdritic cells, macrophages, thymic epithelia.

148. True.

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