Our bodies are covered in bacteria. Some of the bacteria may be harmful. If our skin is broken, bacteria may get inside us. Immune cells called neutrophils ingest and destroy the bacteria. Many neutrophils are killed in the process, forming pus.
Macrophages are attracted by the dead cells and come to engulf and ingest them. However, some bacteria avoid the neutrophils and enter the body.
A dendritic cell, scouting for pathogens, finds the bacteria and engulfs some. Antigens appear on the surface of the dendritic cell.
The dendritic cell migrates to the nearest lymph nodes and displays the bacterial antigen on its surface. If T cells entering the lymph node recognise the antigen, they become activated and replicate.
Activated T helper cells interact with B cells. If a B cell recognises the same antigen, it replicates and matures into antibody-producing plasma cells.
Some of the replicated B cells mature into memory cells in case this bacteria appears again. Then the response will be stronger and faster.
The activated cells move out of the lymph node to the site where the dendritic cell found the bacteria.
The plasma B cells release antibodies. The antibodies lock on to the bacteria surface, which disables it from functioning and flags it for destruction.
The macrophage is attracted to the marked or flagged bacteria. The macrophage engulfs and ingests the bacteria.
Suppressor T cells come in to calm the immune cells and stop the fighting.