Once thought that systemic diseases increased the incidence of periodontal disease and exacerbated periodontal conditions, recent medical research has shown that periodontal disease can actually increase risks for cardiovascular disease, respiratory diseases, osteoporosis, preterm delivery and low birth weight infants, obesity, and accelerate the progression of diabetes. Examples of systemic conditions and risk factors that contribute to oral inflammation are uncontrolled diabetes, leukemia, pregnancy, puberty, pemphigus, HIV infection, concomitant use of medications, genetics, nutrition, smoking, stress, and substance abuse. Therefore, the relationship between oral and systemic health goes both ways such that each entity can positively or negatively influence the other. This statement, however, should not be surprising since the mouth is connected to our body.
The general idea of how oral iflammation can affect the immune system is that gum disease is an inflammatory process caused by oral bacteria. While in the blood stream, these periodontal and oral bacteria affects an individual's immune system by triggering more inflammatory processes (in a remote area from the mouth), which in turn results in the disruption of systemic health.
Therefore any form of oral inflammation must be treated and controlled for your overall well being.