Intrinsic Immunity - Relationship To The Immune System

Relationship To The Immune System

Intrinsic Immunity combines aspects of the two traditional branches of the immune system - adaptive and innate immunity – but is mechanistically distinct. Innate cellular immunity recognizes viral infection using toll-like receptors (TLRs), or pattern recognition receptors, which sense Pathogen-associated molecular patterns (PAMPs), triggering the expression of nonspecific antiviral proteins. Intrinsic immune proteins, however, are specific both in virus recognition and their mechanism of viral attenuation. Like innate immunity, however, the intrinsic immune system does not respond differently upon repeat infection by the same pathogen. Also, like adaptive immunity, intrinsic immunity is specifically tailored to a single type or class of pathogens, notably retroviruses.

Unlike adaptive and innate immunity, which must sense the infection to be turned on (and can in the case of adaptive immunity, take weeks to become effective) intrinsic immune proteins are constitutively expressed and ready to shut down infection immediately following viral entry. This is particularly important in retroviral infections since viral integration into the host genome occurs quickly after entry and reverse transcription and is largely irreversible.

Because the production of intrinsic immune mediating proteins cannot be increased during infection, these defenses can become saturated and ineffective if a cell is infected with a high level of virus.