CAR-T cell therapy typically targets which B-cell antigen?

• A. CD4
• B. CD3
• C. CD8
• D. CD19

Answer: (D)

CAR-T therapy is designed to recognize a specific antigen on tumor cells and trigger T-cell–mediated killing. CD19 is a surface protein present on nearly all B-lineage cells, including most B-cell cancers, making it an ideal and widely applicable target. Targeting CD19 allows the engineered T cells to bind and kill malignant B cells while sparing most non-B cells, though it can cause B-cell aplasia as a predictable on-target effect.

In contrast, the other markers are T-cell–associated. CD4 and CD8 mark T-cell subsets, not B-cell tumors, so directing CAR-T to these would not selectively target B-cell cancers. CD3 is part of the T-cell receptor complex on all T cells, not a B-cell antigen, so targeting it would broadly affect T cells rather than selectively eliminating B-lineage malignancies.