The immune system

This interactive explains the different cells, micro-organisms and molecules involved in the human immune system.

To use this interactive, move your mouse or finger over any of the labelled boxes and select to obtain more information.

Transcript

Inside a lymph vessel

Dendritic cells

Dendritic cells are a bit like spies sitting in among other cells. If they detect pathogens (foreign substances) within the body, they will ingest some, and molecules of the pathogens, called antigens, appear on the surface of the dendritic cell. The dendritic cell then leaves the site of infection and moves to the nearest lymph node. It stays there for about a week, displaying the antigens to the T and B cells that move through the lymph node.

Acknowledgement: Prof Gareth Jones, Wellcome Images

Macrophages

Macrophage means ‘big eater’. These cells ingest and clean up messes that include disabled cells or viruses that have been flagged with antibodies and dead cells.

Acknowledgement: MRC NIMR, Wellcome Images

Inside a lymph node

T helper cells

T helper cells are co-ordinator cells. They give instructions to other cells by secreting certain proteins, called cytokines. T helper cells are responsible for activating other immune cells. Each T helper cell can only recognise one antigen.

Acknowledgement: David Darling

Suppressor T cells

When the infection is gone, the immune system needs to be calmed down or killer T cells may keep on killing good cells. The suppressor T cells (or regulatory cells) slow down or turn off the immune system to prevent damage to good cells.

Acknowledgement: Public domain

Killer T cells

Killer T cells (or cytotoxic T cells) destroy pathogen-infected cells by shooting an enzyme into them. This makes the cell break into small pieces that can be eaten by nearby macrophages.

Acknowledgement: Science Online, BSIP Lecaque/Science Photo Library

B cells

When stimulated by the presence of a particular antigen, B cells mature to become antibody factories known as plasma cells, which release antibodies specifically to target that antigen.

Acknowledgement: Mesoblast Limited

Inside a blood vessel

Antigens

Antigens are molecules from pathogens or foreign substances such as bacteria or viruses. Antigens appear on the surface of cells that have ingested or been invaded by pathogens and cause the immune system to respond.

Acknowledgement: Centers for Disease Control and Prevention

Antibodies

Antibodies are released by plasma cells that are produced by B cells. Antibodies attach to the specific antigen they were produced for, disabling and marking the pathogen for disposal.

Acknowledgement: The University of Waikato

Bacteria

Bacteria are single-celled microscopic organisms. While most bacteria are harmless, some are pathogenic and cause us harm.

Acknowledgement: Centers for Disease Control and Prevention, Dr Ray Butler

Viruses

Viruses are very basic (and tiny) microorganisms that are not considered living. A virus is genetic material wrapped up in a protein coat. Viruses hijack cells and use the cells to replicate themselves. Viruses can be pathogenic and cause us harm.

Acknowledgement: Sebastian Kaulitzki

Neutrophils

Neutrophils are often the first cells to leave the blood and fight incoming pathogens. They only live a few days. Dead neutrophils accumulate as pus.