SBA — Single Best Answer · Review
Question 611
Immunology → General
Classification
Question
SSBAQuestion Header
A lymphocyte lyses virus-infected and allograft target cells bearing foreign antigens. Which phenotype is most consistent with this function?
Question Stem
Select the single best answer.
Options
A
CD8 positive with MHC class I restriction
B
CD4 positive with MHC class II restriction
C
CD19 positive with surface immunoglobulin
D
CD16 and CD56 positive but CD3 negative
E
CD68 positive
Explanation
Cytotoxic T lymphocytes are CD8 positive and MHC class I restricted. They kill target cells bearing new or foreign antigens, including tumour cells, allograft cells and virus-infected cells.
Option Validity
B) CD4 positivity with MHC class II restriction characterises helper/inducer T cells.
C) CD19 and surface immunoglobulin are B-cell features.
D) CD3-negative, CD16/CD56-positive cells are natural killer cells.
E) CD68 is associated with macrophages.
Further Reading
Saxena MRCOG-1 Basic Sciences — Immunology: T-lymphocyte functions, printed page 210.