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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.
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Could you please provide an explanation for the correct answer and the rest of the options?
Thank you so much
Elpida
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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.
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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.
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Thank you so much for providing the explanation
