Question

On infection by a specific virus, a host generates cytotoxic T cells that kill:

• A. infected cells expressing self MHC
• B. infected cells expressing MHC of different genotype
• C. uninfected cells expressing self MHC
• D. cells infected by an unrelated virus, expressing self MHC

Hint:

In immune response, cytotoxic T cells destroy infected cells by recognizing foreign MHC.

Answer 1

The Correct Option is A

Step 1: Understanding MHC and T cell response.
MHC (Major Histocompatibility Complex) molecules are critical for immune system function. Cytotoxic T cells recognize infected cells that display foreign antigens via MHC molecules. T cells then destroy these infected cells.

Step 2: Analyzing the options.
- (A) infected cells expressing self MHC: Cytotoxic T cells would not recognize these cells as infected since they are expressing "self" MHC.
- (B) infected cells expressing MHC of different genotype: Correct — Cytotoxic T cells recognize foreign MHC and trigger destruction of the infected cells.
- (C) uninfected cells expressing self MHC: These cells would not be targeted, as there is no foreign antigen.
- (D) cells infected by an unrelated virus, expressing self MHC: This does not match the situation described in the question.

Step 3: Conclusion.
The correct answer is (B) because cytotoxic T cells target infected cells expressing foreign MHC.