Immunology | iGEM Project Cargo

2 Minute Read


The immune system is a robust and deeply complicated system. Here’s everything you should know in one neat bundle

by JiaXun Li

Immunity is the ability our human body has to resist foreign and harmful microorganisms and the immune system is a group of cells and tissues that elicit an immune response and defend the body against infections.

Innate Immunity

Immunity consists of two main components: innate immunity and adaptive immunity. The innate immune response is the primary line of defense against a broad group of common antigens. When the antigens attack the body, the anatomical barriers like skin, eyes, respiratory airways, and lungs physically prevent them from entering the body. The sweat on the skin, tear secreted by the eyes, and the mucus produced in the lungs can remove or kill most of the infectious agents or create an unsuitable environment for those antigens [1].

For those antigens that cannot be eliminated by anatomical barriers, they damage cells and tissues and trigger inflammatory responses, including redness, heat, pain, and swelling, and phagocytosis [2]. Being attacked by antigens, cells release a chemical called histamine which attracts macrophages and neutrophils to destroy the antigens. Macrophages can kill antigens using phagocytosis, which is to swallow antigens alive, digest them inside their cytoplasm using a digestive enzyme secreted into the phagocytic vacuole. Neutrophils not only engulf bacteria but also cluster together and cover the antigens with antibodies which stimulate more neutrophils to attack them. This process is noticed as inflammation. Generally speaking, inflammation is a process to eliminate the initial cause of cell injury and tissue damage. If the antigens are too unable to be eliminated, we still have dendritic cells which not only “eat” and kill antigens but also behave like a link between innate and adaptive immune systems, tagging antigens so that the adaptive immune system can recognize them [3].

Adaptive Immunity

The adaptive immune system is carried out by two types of lymphocytes: T cells and B cells. Once the T cells are activated by matching the antibodies wrapped on antigens and the receptors on themselves, they can either be a helper T cell releasing cytokines that activate B cells and macrophages or other T cells known as killer T cells or become killer T cells themselves, cloning by mitosis and cleaning antigens by secreting toxic substance and punching holes to kill them. Once the B cells are activated by helper T cells, some of them become plasma cells, secreting antibodies and completely clearing the antigens, while the rest of them become memory cells, remaining circulating in the body for a long time and being ready for the next antigen attack.


[1] IMMUNOLOGY - CHAPTER ONE - INNATE (NON-SPECIFIC) IMMUNITY Gene Mayer, Ph.D. Immunology Section of Microbiology and Immunology On-line. University of South Carolina [2]Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. Innate Immunity [3]Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walters P (2002). Molecular Biology of the Cell (Fourth ed.). New York and London: Garland Science. ISBN 0-8153-3218-1.