Acquired Immunity
பெறப்பட்ட நோய் எதிர்ப்பு சக்தி
Innate immunity is your body's blunt force; Acquired immunity is its precision sniper. If you confuse 'memory' with 'non-specific response,' you lose 4 marks instantly. Pathogen-specificity is the hallmark of adaptive defense.
The idea
Acquired immunity is pathogen-specific and characterized by immunological memory. Upon the first encounter with a pathogen, the body mounts a primary response of low intensity. Subsequent encounters with the same pathogen trigger a highly intensified secondary or anamnestic response. This system relies on two specialized lymphocytes: B-lymphocytes for humoral response and T-lymphocytes for cell-mediated response.
Why it matters
It allows the immune system to 'learn' and remember specific pathogens, providing long-term protection and faster responses to recurring infections.
NEET lens
NEET focuses on the distinction between primary and secondary responses. Memorize that secondary response is anamnestic and faster due to memory cells. Expect questions on the roles of B and T cells; remember, T-cells do not secrete antibodies but help B-cells do so. Do not confuse this with innate barriers.
Clinical significance
When this system fails, the body cannot distinguish self from non-self, leading to autoimmune diseases like Rheumatoid Arthritis. Conversely, immunodeficiency disorders like AIDS occur when T-lymphocytes are depleted, rendering the acquired immune system non-functional.
Introduction
Acquired immunity is pathogen-specific and has memory. The body responds weakly the first time it meets a pathogen and much more strongly the next time.
Core concept
Primary response: on first encounter, a low-intensity response. Secondary (anamnestic) response: on later encounters with the same pathogen, a highly intensified response — the body remembers the first encounter. Two types of lymphocytes carry this out: B-lymphocytes produce antibodies (proteins) into the blood — humoral immune response; T-lymphocytes help B cells produce antibodies and mediate cell-mediated immunity (CMI). CMI is responsible for graft rejection: the body can distinguish 'self' from 'nonself', so tissue matching and blood group matching are essential before transplants, and patients take immunosuppressants afterwards. Loss of the ability to distinguish self from non-self leads to autoimmune diseases (e.g. rheumatoid arthritis).
Go deeper
Acquired immunity is not present at birth; it develops during life. Vaccination uses this memory: a weakened or inactivated pathogen (or its proteins) primes the body so a real infection triggers a fast secondary response.
From Class 10
Once you have had chickenpox, you rarely get it again — your immune system remembers it. That memory is acquired immunity.