When a cell or host is defined as permissive in virology, it refers to the fact that the virus is able to circumvent host defenses and is able to replicate. Usually this occurs when the virus has modulated one or several of the host cellular intrinsic defenses, and the host immune system. 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 [N.J. Dimmock et al. "Introduction to Modern Virology, 6th edition." Blackwell Publishing, 2007.] .

Susceptible versus Permissive

The significance between the difference of the two has now been elucidated with study of the rabbit-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 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 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.] .


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  • Permissive — Per*mis sive, a. 1. Permitting; granting leave or liberty. By his permissive will. Milton. [1913 Webster] 2. Permitted; tolerated; suffered. Milton. [1913 Webster] …   The Collaborative International Dictionary of English

  • permissive — c.1600, allowing to pass through, from O.Fr. permissif, from L. permissus, pp. of permittere (see PERMIT (Cf. permit) (v.)). In sense of tolerant, liberal it is first recorded 1956; by 1966 it had definite overtones of sexual freedom …   Etymology dictionary

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  • permissive — ► ADJECTIVE 1) allowing or characterized by freedom of behaviour, especially in sexual matters. 2) Law allowed but not obligatory; optional. DERIVATIVES permissively adverb permissiveness noun …   English terms dictionary

  • permissive — [pər mis′iv] adj. [ME < MFr permissif < ML permissivus < pp. of L permittere] 1. giving permission; that permits 2. allowing freedom; esp., tolerant of behavior or practices disapproved of by others; indulgent; lenient 3. Archaic… …   English World dictionary

  • permissive — [[t]pə(r)mɪ̱sɪv[/t]] ADJ GRADED A permissive person, society, or way of behaving allows or tolerates things which other people disapprove of. The call for law and order replaced the permissive tolerance of the 1960s... Single parents are more… …   English dictionary

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  • permissive — per·mis·sive pər mis iv adj supporting genetic replication (as of a virus) <permissive temperatures> <permissive monkey cells> …   Medical dictionary

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