Question X. The MHC class II transactivator (CIITA), does not directly bind to D

Question

Question X. The MHC class II transactivator (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. A genetic defect in this transcriptional coactivation (caused by various CIITA mutations) results in an inability to synthesize MHC class II molecules, which 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 (140-145) as either factually correct (true) or incorrect (false)]:

140. 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.

141.the cytolytic activity of CD8+ T cells (= the capacity of individual cytotoxic CD8+ T cells to kill their target cells) from the CIITA mice will be reduced compared to that of wild-type mice.

142. 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.
143. the frequency of peripheral CD4+ T cells will be very low in the CIITA-deficient mice.
144. the T-cell recognition of all peptides, which are >7 AA residues long, will be defective in the CIITA-deficient mice.

145. the T-cell recognition of all peptides, which are >12 AA residues long, will be defective in the CIITA-deficient mice.

Explanation / Answer

144 and 145 are false

The T-cells from CIITA deficient mice , proliferated normally after their activation with  ConA or anti-CD3 antibody.This shows that the TCR mediated response is not affected in CIITA deficient mice and hence the T-cell recognition of peptides will not be defective

143 is true

The T-cells from CIITA defiecient mice did not proliferate against spleenocytes from bm12 mice. The MHC of bm12 mice only differs at the MHC class 2 locus. This shows that the CD4+ T cells response is reduced and it is due to the low frequency of CD4+ T cells in CIITA deficient mice.

142 is false

The Tcells eventhough less in amount will have the function to negatively select the autoreactive t cells .

141 is true

140 is false

The Tcells from the CIITA deficient mice will have both th1 and th2 polarization.

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.