Common questions about Immune system

Short answers, pulled from the story.

What is the immune system and how does it protect an organism from disease?

The immune system is a vast, decentralized network of biological systems that operates silently to protect an organism from disease. It detects and responds to a wide variety of pathogens, such as viruses, bacteria, and parasites, as well as cancer cells and foreign objects like wood splinters. This complex defense mechanism is found in nearly all organisms, from bacteria that use rudimentary enzymes to jawed vertebrates that possess sophisticated adaptive responses.

How does the immune system distinguish between self and non-self to prevent autoimmune diseases?

The immune system distinguishes between self and non-self by recognizing specific non-self antigens during a process called antigen presentation. Dysfunction of this distinction can cause autoimmune diseases, inflammatory diseases, and cancer, revealing the delicate balance required for health. Autoimmunity results from a hyperactive immune system attacking normal tissues as if they were foreign organisms, with common autoimmune diseases including Hashimoto's thyroiditis, rheumatoid arthritis, diabetes mellitus type 1, and systemic lupus erythematosus.

When did the first known reference to immunity occur and who documented it?

The first known reference to immunity occurred during the plague of Athens in 430 BC, where Thucydides noted that people who had recovered from a previous bout of disease could nurse the sick without contracting the illness a second time. In the 10th century, Persian physician al-Razi wrote the first recorded theory of acquired immunity, noting that a smallpox bout protected its survivors from future infections. The field advanced significantly in the 19th century through the work of Paul Ehrlich, who proposed the side-chain theory to explain the specificity of the antigen-antibody reaction, earning him a joint Nobel Prize in 1908 with Elie Metchnikoff.

What are the main types of cells in the adaptive immune system and what do they do?

The cells of the adaptive immune system are special types of leukocytes called lymphocytes, with B cells and T cells being the major types. B cells are involved in the humoral immune response, producing antibodies that circulate in blood plasma and lymph to bind to pathogens and mark them for destruction. T cells are involved in cell-mediated immune response, with killer T cells killing cells infected with viruses and helper T cells regulating both the innate and adaptive immune responses.

How do pathogens evade the immune system and why do some vaccines fail?

Pathogens evade the immune system by hiding within host cells, forming biofilms, or generating surface proteins that bind to antibodies and render them ineffective. Mechanisms used to evade the adaptive immune system include antigenic variation, where pathogens like HIV rapidly change non-essential epitopes on their surface while keeping essential epitopes concealed. This constant mutation explains the failures of vaccines directed at this virus, as the proteins on its viral envelope that are essential for entry into its host target cell are constantly changing.

Read the full story about Immune system →