Immune response

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== Immune Response ==

The immune response is the body's defense mechanism against pathogens, such as bacteria, viruses, and other harmful agents. It involves a complex network of cells, tissues, and organs that work together to identify and neutralize foreign invaders.

Components of the Immune System

The immune system is divided into two main components: the innate immune system and the adaptive immune system.

Innate Immune System

The innate immune system is the body's first line of defense and responds to pathogens in a generic way. It includes physical barriers like the skin and mucous membranes, as well as immune cells such as macrophages, neutrophils, and natural killer cells.

Adaptive Immune System

The adaptive immune system is more specialized and can remember specific pathogens for faster responses in future encounters. It involves lymphocytes, including B cells and T cells. B cells produce antibodies that neutralize pathogens, while T cells destroy infected cells.

Stages of the Immune Response

The immune response can be divided into several stages:

Recognition

The immune system recognizes pathogens through antigens, which are molecules found on the surface of pathogens. Antigen-presenting cells (APCs) such as dendritic cells capture and present these antigens to T cells.

Activation

Once antigens are recognized, the immune system is activated. T cells proliferate and differentiate into various subtypes, including helper T cells and cytotoxic T cells. Helper T cells assist in activating B cells, while cytotoxic T cells kill infected cells.

Response

Activated B cells produce antibodies that bind to antigens, marking them for destruction by other immune cells. Cytotoxic T cells directly attack and destroy infected cells.

Memory

After the pathogen is eliminated, some T and B cells become memory cells. These cells remain in the body and provide a faster and more efficient response if the same pathogen is encountered again.

Disorders of the Immune System

The immune system can sometimes malfunction, leading to various disorders:

• Autoimmune diseases: The immune system mistakenly attacks the body's own cells. Examples include rheumatoid arthritis and lupus.
• Immunodeficiency: The immune system is weakened and cannot effectively respond to infections. Examples include HIV/AIDS and SCID.
• Allergies: The immune system overreacts to harmless substances, such as pollen or pet dander.

Related Pages

• Pathogen
• Antigen
• Antibody
• Lymphocyte
• Autoimmune disease
• Immunodeficiency
• Allergy