+- USMLE Forum - Largest USMLE Community (https://www.usmleforum.com)
+-- Forum: USMLE Forum (https://www.usmleforum.com/forumdisplay.php?fid=1)
+--- Forum: Step 1 (https://www.usmleforum.com/forumdisplay.php?fid=2)
+--- Thread: Non NBME question....COME ON ! - kindmd (/showthread.php?tid=652878)
Non NBME question....COME ON ! - kindmd - ArchivalUser - 02-07-2012
A 28-year-old nurse experiencing lethargy was diagnosed with advanced metastatic melanoma. In vitro testing revealed normal lymphocyte responses to concanavalin A and tetanus, but decreased CD8+ lymphocyte response to tumor antigens. Molecular analysis of tumor gene expression was performed. Expression of which gene is likely deficient in this patient?
A. CD1.
B. CD3.
C. Human leucocyte antigen-DP (HLA-DP).
D. RAG-1.
E. TAP-1.
0 - ArchivalUser - 02-07-2012
bb?
0 - ArchivalUser - 02-07-2012
no one else ?
0 - ArchivalUser - 02-07-2012
It's ***E*** !
0 - ArchivalUser - 02-08-2012
Could you please provide an explanation for the correct answer and the rest of the options?
Thank you so much
Elpida
0 - ArchivalUser - 02-08-2012
Explanation for E:
Metastatic melanoma is often characterized by loss of immunodominant T-cell reactivity to tumor antigens MART-1 and Melan-A. The TAP-1 and TAP-2 proteins are peptide transporters that shuttle endogenous derived peptides (8 to 9 amino acids) from the cytosol into the endoplasmic reticulum for binding to major histocompatibility complex (MHC) class I proteins, involved in antigen (Ag) processing to CD8+ T cells. TAP deficiency has been reported in certain human tumor cells, thus allowing them evade detection by CD8+ cytotoxic cell surveillance.
0 - ArchivalUser - 02-08-2012
Explanation for B:
CD3 on the surface of lymphocytes assists in signal transfer after the T-cell receptor has engaged antigen. In this case, the CD4+ cells exhibit positive response to tetanus antigen, thus ruling out defect in this gene.
0 - ArchivalUser - 02-09-2012
Thank you so much for providing the explanation