- A substance of microbial origin postulated to inhibit the resistance mechanisms of the host. [L. agressor, an assailant, fr. ad-gredio, pp. -gressus, to attack]
* * *ag·gres·sin ə-'gres-ən n a hypothetical substance held to contribute to the virulence of pathogenic bacteria by paralyzing the host defensive mechanisms (as the white blood cells) and held to be produced by the bacteria in the body of the host
* * *ag·gres·sin (ə-gresґin) any of a postulated group of nontoxic substances produced by pathogenic bacteria that inhibit the mechanisms of host resistance.
Medical dictionary. 2011.