Question

When harmful bacteria enter the body through a cut, the immune system must act quickly to protect health. Different types of cells sendand receive messages that help coordinate the defense. These signals allow the body to detect the problem, call for reinforcements, and organize a response that eliminates the threat while keeping the system balanced.

Place the steps of cell communication during an immune response in the correct order.

Number Sequence Immune Response Description
1
2
3
4
5
6

Answer 1

1) Resident innate immune cells (macrophages, dendritic cells) detect bacteria entering through the cut using pattern-recognition receptors.
2) Those cells phagocytose bacteria, process bacterial proteins and display peptide antigens on MHC molecules, and secrete cytokines/chemokines as danger signals.
3) Cytokines/chemokines trigger inflammation — they dilate blood vessels and recruit neutrophils and other leukocytes to the infection site.
4) Activated dendritic cells migrate to nearby lymph nodes and present antigen‑MHC complexes to naive T cells, providing co‑stimulation.
5) Antigen-specific T cells (helper T cells and cytotoxic T cells) and B cells are activated and proliferate; helper T cells secrete cytokines that drive B cells to become antibody‑secreting plasma cells.
6) Antibodies and effector cells neutralize and/or kill the bacteria (opsonization, complement activation, cytotoxicity); regulatory signals (regulatory T cells and anti‑inflammatory cytokines) then downregulate the response to restore tissue homeostasis.