A human cell with CD8 on its surface is most likely a

A human cell with CD8 on its surface is most likely a

• A. B cell
• B. Monocyte
• C. T-helper cell
• D. Cytotoxic T cell

Answer: (D)

A cell bearing CD8 on its surface is characteristic of a cytotoxic T cell. CD8 acts as a co-receptor for the T-cell receptor, guiding recognition of antigens presented by MHC class I molecules, which are found on nearly all nucleated cells. This positioning lets cytotoxic T cells identify and destroy virus-infected or abnormal cells directly, a key part of cell-mediated immunity. In contrast, T-helper cells carry CD4, not CD8, and B cells or monocytes have different surface markers (B cells express markers like CD19/CD20 and surface immunoglobulin; monocytes express markers such as CD14). So CD8 specifically points to cytotoxic T cells.

A cell bearing CD8 on its surface is characteristic of a cytotoxic T cell. CD8 acts as a co-receptor for the T-cell receptor, guiding recognition of antigens presented by MHC class I molecules, which are found on nearly all nucleated cells. This positioning lets cytotoxic T cells identify and destroy virus-infected or abnormal cells directly, a key part of cell-mediated immunity. In contrast, T-helper cells carry CD4, not CD8, and B cells or monocytes have different surface markers (B cells express markers like CD19/CD20 and surface immunoglobulin; monocytes express markers such as CD14). So CD8 specifically points to cytotoxic T cells.