They remember the antigen and are ready to attack if it enters the body again. Memory T-cells form the basis of our acquired (adaptive) immune response. T lymphocyte functionsĪfter an antigen has been destroyed, most effector T cells die however, a small proportion differentiates into memory T-cells. An effector T cell is also called a cytotoxic T cell. As an effector cell (causing an effect) it can destroy the presented antigen. After a naïve T-lymphocyte has made contact with an antigen-presenting dendritic cell (or other APC type) it differentiates into an effector T cell. Naïve describes the original form of a mature T-lymphocyte as it leaves the lymphoid organ of the thymus. Just like dendritic cells, a T-lymphocyte (T cell) changes its status when it comes into contact with and recognizes an antigen. Dendritic Cells Function: Innate Immunity to Adaptive Immunityĭendritic cells’ most important role after antigen capture is the activation of naïve T lymphocytes. They affect their own cell as autocrine messengers, neighboring cells as paracrine messengers, and travel through the bloodstream to affect more distant targets. Cytokines stimulate or inhibit cell growth, cell death, inflammation, cell differentiation, and cell migration. This broad group includes interferons which you may recognize as the main component of some antiviral drugs. Dendritic cells perform phagocytosis and preserve information from ingested particles that can kick-start adaptive (acquired) immune responses.Ĭytokines are signaling molecules. Macrophages and neutrophils scavenge and destroy harmful or foreign particles and release chemicals that attract more white blood cells. Like macrophages and neutrophils, dendritic cells are phagocytes. Phagocytic cells wrap around foreign particles and toxins and digest them. These chemicals open local blood vessels and attract more phagocytic cells. White blood cells release chemical factors such as histamine, prostaglandin, and bradykinin. Coughing and sneezing rids us of countless pathogens every day. A fever helps, as many bacteria will die at temperatures higher than normal body temperature. By increasing blood flow to the area, more white blood cells arrive to destroy the intruders. The first step after PAMP or DAMP recognition is the inflammatory reaction. A single pattern recognition receptor can recognize both pathogen- and damage-associated patterns. Many types of cells, including dendritic cells, have pattern recognition receptors (PRRs). Pathogen-associated molecular pattern signaling The macrophage catches and digests the bacteria (phagocytosis). Cytokines tell other cells that an attack is underway.

Upon detection, the macrophage then secretes cytokines in response. The macrophage has receptors for the LPS pattern that detect the PAMPS. The following image shows the invasion of pink antigen bacteria with PAMPs in the form of LPS (lipopolysaccharide) on their outer membranes. Our pwn cells, when damaged, dying or dead, present with DAMPs (damage-associated molecular patterns). All microbes have similar general patterns of molecules known as PAMPs (pathogen-associated molecular patterns) on their outer surfaces. If an antigen enters the body and survives despite these anatomical barriers, the next phase in the innate immune system defense mechanism takes over. These anatomical barriers are part of the innate immune system. These include skin, stomach acid, airway mucus, the blood-brain barrier, sweat, and tears. Most vertebrates have multiple protective barriers. Antigens range from viruses and bacteria to chemicals released from damaged cells when they are burned, scratched, starved of oxygen, or otherwise traumatized.

The innate immune system is a nonspecific mode of protection that occurs before, at, or within a short time of antigen exposure. Antigens and antibodies Dendritic Cell Function: Innate Immune System Antibodies are a later stage of immunity that will be described further on. In the image, the orange antigens with many surface proteins have been detected by antibodies – the Y-shaped blue-green particles. This is because certain patterns of molecules on the antigen or on damaged cell membranes make them recognizable. The presence of an antigen – or its surface proteins – stimulates an immune response. Dendritic cells have an important function in the innate immune system where they carry out surveillance duties, looking for antigens in the form of endogenous toxins and exogenous foreign substances.

Dendrite functions