Which term best describes the cells that present antigens to trigger a broader immune response?

• A. Antigen-Presenting Cells
• B. Killer Cells
• C. Null Cells
• D. Plasma Cells

Answer: (A)

Antigen presentation is how the immune system shows pieces of a pathogen to T cells, starting and shaping the broader adaptive response. Cells that perform this crucial role are antigen-presenting cells, such as dendritic cells, macrophages, and B cells. They capture the antigen, process it, and display peptide fragments on MHC molecules to T helper cells, providing the necessary signals to activate those T cells and, in turn, stimulate B cells to produce antibodies and cytotoxic T cells to target infected cells. This presentation links innate sensing with the tailored immune response, coordinating a broad, effective defense. The other options describe cells specialized for different tasks: killer cells directly attack infected cells, null cells refer to cells lacking specific markers, and plasma cells are antibody factories rather than presenters of antigens.