Components of Innate Immunity

When an infection or illness initially manifests, the innate immune system is the one to react. In all multicellular creatures, the innate immune response is present in some form. Natural or native immunity are other names for innate immunity, which serves as the first line of defense against germs.

• It is made up of cellular and molecular defense systems that are ready to react quickly to infections even before they occur.
• Innate immune system mechanisms may not be able to discern minute variations between microorganisms since they are specialized for features shared by groups of related microbes.

Key Terms: Immunity, immune system, infections, innate immunity, adaptive immunity, humoral immunity, inflammation

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What is Innate immunity?

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Innate immunity, also referred to as non-specific immunity, is the natural defense mechanism present from birth. It provides protection against all antigens for humans. Barriers that prevent hazardous substances from entering one’s body are a part of innate immunity. These obstacles act as the first line of defense for the immune system. The innate immune system is a well-established immunological approach and the primary host defense mechanism.

• When a pathogen enters the body, the innate immune system first recognizes it, and only then does the adaptive immune system become active.
• Illustrations of innate immunity encompass responses like coughing, tear enzymes, and skin oils.
• Mucus is a bacterial and particle-trapping substance, an acidic stomach.
• Innate humoral immunity pertains to protein-based aspects of innate immunity.
• The complement system in the body, interferon, and interleukin-1 (which induces fever) are a few examples.
• If an antigen manages to get past these barriers, additional immune system components will attack and eliminate it.

Read More: Difference Between Antigen and Antibody

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Components of the Innate Immune System

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There are four key parts of the innate immune system that support the defense mechanism:

1. Anatomical Barriers to Innate Immunity

Mechanical, chemical, and biological barriers make up the anatomical barrier of innate immunity, which serves as the first line of defense against the pathogen.

• Mechanical or physical barriers: Mechanical or physical barriers prevent germs from physically entering the body.
  • Because of the epidermis, the skin is the initial mechanical barrier that makes it difficult for infections to enter.
  • Pathogens cannot enter the skin through the hair, a skin accessory organ. 
  • Mechanical barriers also include mucous membranes in the respiratory, digestive, and urine tracts.

• Chemical barriers: Chemical barriers prevent infections from entering the body through apertures and internal body surfaces. Sweat, lactation, mucus, saliva, tears, and semen are a few examples of chemical barriers.
  • Because vaginal discharge is acidic, germs cannot survive it.
  • Pathogens cannot tolerate the zinc included in semen.
  • Foreign intruders are also killed by the digestive fluids generated in the stomach.

• Biological barriers: Biological barriers to innate immunity, urinary, gastrointestinal, and reproductive systems all contain a variety of beneficial bacteria that prevent infections and dangerous bacteria from thriving within bodies.

2. Cellular Response

Different types of leukocytes from the innate immune system's cellular response phagocytose pathogens to death. The infections that infiltrate the bodies are killed only by these leukocytes, which circulate in the blood.

• Phagocytosis is a crucial cellular mechanism where a cell extends its plasma membrane to swallow bigger and more dangerous particles.
• The phagocytic cell expands its plasma membrane during this process to enclose the pathogen within and create a vesicle known as a phagosome.
• The phagosome and lysosome subsequently joined to form the phagolysosome.
• The pathogens are eliminated by the lysosome's acid and digesting enzyme secretions. 
• Dendritic cells, macrophages, and neutrophils are the cells engaged in phagocytosis.

Read More: Blood Coagulation

3. Blood Proteins

A variety of proteins are produced by the hepatocytes, or liver cells, which kill invasive infections. The complement system causes the production of these proteins. The power of antibodies to destroy infections is complemented by the complement system, a metabolic cascade. The complement system's proteins function in many ways.

• They aid in attracting inflammatory cells.
• They cover the pathogen's surface, giving it a simple target for eradication. It creates a hole in the pathogen cell wall, cytolysis, and kills it.
• The body's neutralized antibody-antigen complexes are filtered away by this process.

4. Inflammatory Response

When a pathogen is able to breach anatomical barriers and enter the body, an inflammatory reaction is seen. Redness, swelling, discomfort, and loss of function in the infected region are indicators of inflammation. Histamine and cytokines, which are released by damaged cells and immune system cells like macrophages, act as triggers.

• These substances draw leukocytes that fight pathogens and proteins that repair damaged tissue to the site of the wound. 
• Some cytokines are anti-viral in nature, preventing the host cells' ability to make proteins, which is necessary for the virus to live and reproduce.

Also Read:

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Things to Remember

• The innate immune system, also known as the nonspecific immune system, is an ancient host defense mechanism in vertebrates. It recognizes pathogens before activating the adaptive immune system.
• Mechanical barriers of innate immunity prevent pathogen entry into the body, including skin, hair, and mucous membranes in the urinary, gastrointestinal, and respiratory tracts.
• Innate immunity uses chemical barriers to prevent pathogen entry through bodily openings, surfaces, and secretions.
• Intestinal immunity is protected by biological barriers in the urinary, gastrointestinal, and reproductive tracts.
• Phagocytosis includes leukocytes enveloping pathogens via plasma membranes, creating phagosomes and lysosomes, and discharging acids and enzymes.
• The presence of pathogens initiates inflammation, causing redness, swelling, pain, and function impairment through histamine and cytokines.
• Hepatocytes produce proteins through the complement system, which complements antibodies' ability to kill pathogens.

Also Read:

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Previous Year Questions

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12. Major product of the following reaction is..[JEE Main 2023]
13. The percentage of nitrogen in urea is about..
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