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.

Answer 1

1. Detection: resident innate cells (macrophages/dendritic cells) recognize bacterial molecules and release pro‑inflammatory cytokines and chemokines.
2. Alarm and vascular response: cytokines cause vasodilation and increased blood‑vessel permeability, letting immune cells and fluid into the tissue.
3. Recruitment and immediate attack: chemokine gradients recruit neutrophils and monocytes that migrate into the wound and phagocytose bacteria.
4. Antigen presentation and activation of adaptive immunity: dendritic cells carry processed bacterial antigens to lymph nodes and present them to naïve T cells (with costimulation), activating helper and cytotoxic T cells.
5. Effector phase: helper T cells stimulate B cells to become antibody‑secreting plasma cells and help cytotoxic T cells; antibodies neutralize and opsonize bacteria, enhancing clearance.
6. Resolution and memory: regulatory signals shut down inflammation, tissue repair occurs, and memory B and T cells are formed for faster responses on re‑exposure.