An overview of the immune system as the defense system of the human body

Each subset of TH cells secretes different combinations of substances and thus effect different immune responses. The body generates an excessive immune response to often harmless foreign antigens and damages normal tissues an allergic reaction. There are three types: In the lymph nodes, white blood cells can collect, interact with each other and with antigens, and generate immune responses to foreign substances.

Immune system

Passive memory[ edit ] Newborn infants have no prior exposure to microbes and are particularly vulnerable to infection. Mast cells are cells in tissues that release histamine and other substances involved in inflammatory and allergic reactions.

Each cell type plays a unique role, with different ways of recognizing problems, communicating with other cells, and performing their functions. The immune system is divided into two major branches that provide 1 antigen-specific cell-mediated immunity CMI and 2 humoral immunity see Figure A If the immune system is weakened by another disease, they are also used for protection against infections.

Acute-phase reactions are initiated by proinflammatory cytokines and generally have an acute onset. Antigens may also exist on their own—for example, as food molecules or pollen. Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it.

White blood cells The next line of defense involves white blood cells leukocytes that travel through the bloodstream and into tissues, searching for and attacking microorganisms and other invaders. Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens.

This is also called antibody-dependent or cytotoxic hypersensitivity, and is mediated by IgG and IgM antibodies. Messenger substances of the immune system Besides defense cellsmany soluble substances also contribute to the elimination of pathogens.

After complement component C3 is activated via either the classic or the alternate pathway, C3 cleavage fragments have a variety of actions, as shown.

Several types of white blood cells are involved: The defense mechanisms of the adaptive immune system Last Update: Activated T-cells secrete cytokines that enhance the functions of B-cells and phagocytes and stimulate nonspecific inflammatory responses. Lines of Defense The body has a series of defenses.

T-Cells T-cells are long-lived lymphocytes that circulate continually throughout the body, periodically returning homing to the site of their individual origins. Cytokine actions within the CNS trigger the onset of fever by causing the release of prostaglandins within the temperature-regulating centeranorexia, somnolence, and the release or suppression of hormones produced in the CNS and pituitary gland.

Using this method, cells that have been infected by a virus, for example, can inform the immune system about their state very early from the place of infection in the tissue.

In the humoral arm see Figure A-2humoral immunity is generated by B-cells, which, when stimulated by an antigen plus IL-2 and other cytokines, differentiate into antibody-secreting plasma cells.

New technologies for producing systemic and mucosal immunity by oral immunization: It is believed that they capture antigen or bring it to the lymphoid organs where an immune response is initiated. Nonspecific defensive mechanisms may be active or passive in nature Beisel, If of extreme, immediate, life-threatening severity, they are termed anaphylactic responses.

The unique variable region allows an antibody to recognize its matching antigen. Mucosal surfaces are prime entry points for pathogens, and specialized immune hubs are strategically located in mucosal tissues like the respiratory tract and gut.

T cells recognize a "non-self" target, such as a pathogen, only after antigens small fragments of the pathogen have been processed and presented in combination with a "self" receptor called a major histocompatibility complex MHC molecule. The immune system is characterized by antigen specificity and antigen-related memory.

However, a distinct lymphocyte -derived molecule has been discovered in primitive jawless vertebratessuch as the lamprey and hagfish.

The Immune System -- An Overview

C3b is also the starting point for the lytic pathway, which involves moreOverview of the Immune System. Immune System Research. Immune System Research. The skin is usually the first line of defense against microbes. Skin cells produce and secrete important antimicrobial proteins, and immune cells can be found in specific layers of skin.

Lymph nodes are a communication hub where immune cells sample. Overview of the Immune System and Immunology; Allergic Disorders - Learn about from the MSD Manuals - Medical Professional Version. Molecular Components of the Immune System; Human Leukocyte Antigen (HLA) System and GU tracts form a physical barrier that is the body's first line of defense.

Some of these barriers also have. The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi).

The immune system is composed of many interdependent cell types that collectively protect the body from bacterial, parasitic, fungal, viral infections and from the growth of tumor cells. Many of. A Overview of the Immune System and Other Host Defense Mechanisms William R.

Beisel 1 Immunity, if defined broadly, encompasses all mechanisms and responses used by the body to defend itself against foreign substances, microorganisms, toxins, and noncompatible living cells.

This was taken from Pearson's Human Anatomy & Physiology, 8th Edition to help me study for the tests in the class, it is all of the key bold terms. dose of a disabled or destroyed pathogen used to stimulate a long-term immune defense against the pathogen.

A weakened form of the virus is given to the person so their immune system can build.

An overview of the immune system as the defense system of the human body
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