There are hundreds of different viruses, and some can cause disease in humans.
This is rotavirus, which can spread rapidly on contaminated hands or objects. It damages cells of the small intestine, causing vomiting and diarrhoea. A rotavirus enters the body through the mouth. It travels to the small intestine or gut.
Viruses are tiny. We have magnified this virus so we can track it. The virus attaches to and invades the cells lining the gut.
The damaged cells send out signals to the dendritic cells, which are on the look-out for pathogens.
A dendritic cell can extend between two enterocyte cells. The dendritic cell uses its arm-like part to ‘fish’ for pathogens. The dendritic cell engulfs the virus and breaks it up.
Antigens appear on the surface of the dendritic cell. Meanwhile, some virus particles have begun replicating inside an enterocyte cell.
The dendritic cell migrates to the nearest lymph node and displays the rotavirus antigen on its surface.
If T cells entering the lymph node recognise the antigen they become activated and replicate. Activated T helper cells then 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 the rotavirus 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 rotavirus.
At the site, the B plasma cells release antibodies. The antibodies are picked up and transported through the enterocyte cell. They move into the intestine where they lock on to the antigen on the virus surfaces. This stops the virus from getting into the enterocyte cell, and it is washed away down the gut.
Meanwhile, the rotavirus that invaded the enterocyte cell has replicated.
A killer T cell shoots an enzyme into the enterocyte cell. The enterocyte cell is destroyed, but so is all the rotavirus that was inside the cell.
A macrophage cell is attracted to the dead cell. It engulfs and ingests the cell and the destroyed rotavirus.