{{Other uses, Permissiveness (disambiguation) A permissive cell or permissive host is one that allows a

virus A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...

to circumvent its defenses and replicate. Usually this occurs when the virus has

modulated Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information. The process encodes information in form of the modulation or message ...

one or several of the host cellular intrinsic defenses and the host

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

. The permissive state of a host has now been determined to be the primary factor in determining whether a virus will cause pathological symptoms in a host.

Susceptible ''versus'' permissive

A virus can enter a susceptible cell, but it may or may not be able to replicate. A virus may only replicate in a permissive cell. Viral replication will therefore occur in a susceptible cell which is also a permissive cell that 1) facilitates entry (susceptibility) and 2) supports intracellular replication (permissive cell). The significance of the difference between the two has now been elucidated with study of the

rabbit Rabbits are small mammals in the family Leporidae (which also includes the hares), which is in the order Lagomorpha (which also includes pikas). They are familiar throughout the world as a small herbivore, a prey animal, a domesticated ...

-lethal myxoma virus. Many species of rabbit cells in culture (without the presence of any antiviral defenses that would normally be in a host) can be infected by the myxoma virus, causing infection and cell death. However,

inoculation Inoculation is the act of implanting a pathogen or other microbe or virus into a person or other organism. It is a method of artificially inducing immunity against various infectious diseases. The term "inoculation" is also used more generally ...

of the myxoma virus in many species of rabbit shows that only one species of rabbit is affected, the rest being completely unharmed by the virus (lack of even viral shedding). This has been determined to be a result of the myxoma virus's inability to suppress other species'

interferon Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten ...

expression, and hence resulting in the interferon in turn suppressing the myxoma virus. This is a result of the positive susceptibility of many species of rabbit's cells, but negative permissibility of all but one of the rabbit species' cells.Nash P. et al. "Immunomodulation by viruses: the myxoma virus story." Immunol Rev. 1999 Apr;168:103-20.

Literature

Virology