Innate Immunity
இயல்பான நோய் எதிர்ப்பு சக்தி
Your skin is not just a covering; it is your first line of defense against a microbial onslaught. Innate immunity is non-specific, meaning it does not care who the invader is, only that it is foreign. If you think your body waits for antibodies to fight, you are failing the basics of immunology.
The idea
Innate immunity is inherited and present at birth. It functions through four distinct barriers: physical (skin, mucus), physiological (acid in stomach, saliva, tears), cellular (PMNL-neutrophils, monocytes, macrophages), and cytokine (interferons). These barriers collectively prevent the entry of foreign agents into the body. It is the immediate, non-specific response system.
Why it matters
It provides an immediate, first-line defense mechanism to protect the organism from ubiquitous environmental pathogens before the adaptive immune system is activated.
NEET lens
NEET focuses on the classification of these four barriers. Expect matching-type questions where you must categorize examples like 'tears' under physiological barriers. Do not confuse innate immunity with acquired immunity; innate is non-specific and lacks memory. Memorize the specific role of interferons as they are a high-yield topic for MCQs.
Clinical significance
When these barriers fail, pathogens breach the host, leading to systemic infections. For example, a breach in the physical barrier like a deep cut allows Staphylococcus aureus to cause sepsis. Interferons are critical; they are secreted by virus-infected cells to protect non-infected cells, a mechanism that fails in severe viral outbreaks.
Introduction
Innate immunity is non-specific defence present at the time of birth. It works by putting different barriers in the way of foreign agents.
Core concept
Four barriers (NCERT): (1) Physical barriers — skin, which prevents entry of micro-organisms; mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts traps microbes. (2) Physiological barriers — acid in the stomach, saliva in the mouth, tears from the eyes all prevent microbial growth. (3) Cellular barriers — certain types of leukocytes (WBC) such as polymorpho-nuclear leukocytes (PMNL-neutrophils), monocytes and natural killer cells (a type of lymphocyte) in blood, and macrophages in tissues, can phagocytose and destroy microbes. (4) Cytokine barriers — virus-infected cells secrete proteins called interferons, which protect non-infected cells from further viral infection.
Go deeper
Innate immunity reacts the same way every time; it has no memory. Acquired immunity, by contrast, is specific and remembers past infections.
From Class 10
Your skin, tears and stomach acid are the body's first guards. They block germs without needing to recognise them — that is innate immunity.