The ideas is that any part of the body can be involved in an immune skirmish. The importance of the target organ the nature and extent of problems caused by immune activity. Events in the nose will be experienced as discomfort. Events in the eye or other critical areas of the brain may be catastrophic. The net effect of sustained immune activity in any target organ is inflammation with local dysfunction, associated with systemic symptoms from immune mediators released into the bloodstream.
Lymphocytes are mobile, migratory cells .
Their traffic patterns are fascinating. Lymphocyte populations activated and expanded in mucosal surfaces of GIT or the lung will leave their country of origin and wander inward to travel to other organs. After a holiday in lymph nodes, liver, or spleen, the same lymphocytes seem to wander back to their place of origin. Activated lymphocytes who wander off in other directions are carrying their antigen sensing and reacting properties from one defense unit to another. The traffic patterns of these nomadic cells must have a great deal to do with the success of immune defense and the tenuous balance between reactivity and tolerance.