Immune system

The immune system is a complex network of cells, tissues, and molecules that work together to defend the body against harmful pathogens, such as bacteria, viruses, fungi, and parasites, as well as against abnormal cells like cancer cells. Its primary function is to recognize and eliminate these potential threats while maintaining a delicate balance to avoid attacking the body’s own healthy cells and tissues. Immune system essential for maintaining health It’s dysregulation can lead to various disorders, including autoimmune diseases (where the immune system attacks the body’s own tissues) and immunodeficiency disorders (where the immune system is weakened and unable to effectively fight infections).

The immune system can be broadly categorized into two main components: the innate immune system and the adaptive immune system.

Innate Immune System

The innate immune system provides immediate, non-specific defense against a wide range of pathogens. It acts as the first line of defense and is always active, ready to respond to threats. Key components of the innate immune system include:

Physical and Chemical Barriers:

These include the skin, mucous membranes, and various secretions that create an inhospitable environment for pathogens.

Phagocytes: Cells

like neutrophils and macrophages engulf and digest pathogens through a process called phagocytosis.

Natural Killer (NK) Cells:

NK cells recognize and destroy virus-infected cells and certain types of cancer cells.


Inflammatory responses help contain infections and recruit immune cells to the site of infection or injury.

Complement System:

A group of proteins that, when activated, help destroy pathogens directly and enhance immune responses.

Adaptive Immune System

The adaptive immune system is specific and highly specialized. It takes time to develop but has the ability to “remember” pathogens it has encountered before, leading to faster and stronger responses upon re-exposure. The adaptive immune system consists of the following components:


B cells and T cells are the two main types of lymphocytes involved in adaptive immunity. B cells produce antibodies that can neutralize pathogens, while T cells have various roles, including helping B cells produce antibodies, directly attacking infected cells, and regulating immune responses.


Y-shaped proteins produced by B cells. They can bind to specific pathogens and neutralize them, marking them for destruction by other immune cells.

Major Histocompatibility Complex (MHC):

Molecules that present antigens (pieces of pathogens) to T cells, allowing them to recognize and respond to specific threats.

Memory Cells:

After an initial encounter with a pathogen, memory B cells and T cells are formed. They “remember” the pathogen, leading to a quicker and more robust response upon re-infection.

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