Q.What are interferons? How do interferons check infection of new cells?
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Start your 14-day free trial to unlock the full solution →Interferons are signalling proteins released by virus-infected cells to warn neighbouring healthy cells, triggering antiviral defences that block the infection from spreading.
Interferons are a class of proteins produced naturally by the body’s cells in response to viral infections. They were first discovered in 1957 by Alick Isaacs and Jean Lindenmann, who observed that cells exposed to a killed virus released a substance that “interfered” with the growth of a live virus — hence the name. In the NCERT Class XII Biology textbook, interferons are introduced under the topic of innate immunity, specifically as part of the body’s non-specific defence mechanisms. They are not antibodies; they are cytokines — chemical messengers that coordinate the immune response.
When a virus infects a cell, that cell begins to produce and release interferons into the surrounding tissue fluid. These interferons do not directly kill the virus or protect the infected cell itself. Instead, they act as an early warning system. They travel to neighbouring healthy cells and bind to specific receptors on their surfaces. This binding triggers a cascade of intracellular signals that cause the healthy cells to produce antiviral proteins — such as protein kinase R and 2',5'-oligoadenylate synthetase — which remain inactive until a virus actually enters.
The antiviral proteins produced in response to interferons do not destroy the virus directly. They degrade viral mRNA and inhibit protein synthesis, effectively starving the virus of the machinery it needs to replicate.
Once a neighbouring cell has been “primed” by interferons, if a virus later enters that cell, the antiviral proteins are activated. They chop up viral genetic material and shut down the cell’s own protein-making apparatus, preventing the virus from hijacking the cell to produce more copies of itself. This is how interferons check infection of new cells: they make those cells hostile territory for viral replication. …
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