Helper T-lymphocytes
துணை டி-லிம்போசைட்டுகள்
HIV does not kill the patient; it dismantles the patient's command center. By targeting Helper T-lymphocytes, the virus effectively blinds the entire Cell-Mediated Immunity. If you confuse this with B-lymphocyte function, you lose 4 marks instantly.
The idea
HIV, a retrovirus, enters the body and infects macrophages first. It then targets Helper T-lymphocytes (CD4+ cells) to replicate its viral RNA. This cycle leads to a progressive, rapid decline in the count of these T-cells. The immune system collapses as the primary orchestrator of the immune response is destroyed.
Why it matters
Helper T-cells are the central coordinators of the immune response; their depletion cripples the body's ability to fight off even common pathogens.
NEET lens
NEET asks this repeatedly: identify the 'factory' of the virus and the 'target' cell. Remember, HIV replicates in T-cells, not B-cells. Focus on the phrase 'progressive decrease' in NCERT; examiners often swap this with 'increase' to trap you. 9 questions in 10 years prove this is a high-yield concept.
Clinical significance
When Helper T-cell counts plummet, the body loses its ability to fight common pathogens. This leads to opportunistic infections like Mycobacterium, viruses, and fungi, which a healthy immune system would easily suppress. The patient eventually succumbs to these infections, not the virus itself.
Introduction
Helper T-lymphocytes (TH cells) coordinate the immune response by helping B cells make antibodies and supporting other immune cells. They are the main target of HIV.
Core concept
Role in immunity: T-lymphocytes do not secrete antibodies themselves but help B cells produce them; they also mediate cell-mediated immunity. In HIV infection: the virus first enters macrophages, where its RNA genome is copied into viral DNA by reverse transcriptase; macrophages keep producing virus (acting like an HIV factory). HIV then enters helper T-lymphocytes (TH), replicates and produces progeny viruses that attack other helper T cells. The number of helper T cells decreases progressively, so the person suffers from infections they would normally fight off (e.g. Mycobacterium, viruses, fungi, Toxoplasma).
Go deeper
Because helper T cells coordinate almost every immune response, losing them leaves the body open to opportunistic infections — this is what AIDS is.
From Class 10
Some white blood cells act like managers of the immune system. HIV destroys these managers, so the whole defence system collapses.