Changes in cell surface and circulating soluble adhesion molecules during progression of inflammatory responses. (A) Idealized homeostatic inflammatory response. Schematic showing the hypothetical increase in cell surface adhesion molecules (blue line) associated with onset of inflammation and the subsequent decrease in them during resolution of inflammation. Shedding and accumulation of circulating soluble adhesion molecules similarly rise and fall (green line), but with a lag in time. Points of highest levels of cell surface adhesion molecules (and not necessarily soluble adhesion molecules) should correlate with the greatest levels of overall inflammation and a propensity for collateral tissue damage (red shading). (B) Exaggerated inflammatory and response. Schematic as in (A) illustrating a more severe inflammation and greater initial cell surface adhesion molecule expression, and subsequently greater levels of soluble adhesion molecule production. (C) Aberrant shedding and sustained inflammation. Schematic as in (A) illustrating how a hypothetical deficiency in shedding during inflammation could lead to low levels of soluble adhesion molecules, leaving cell surface adhesion molecules elevated, and allowing for heightened and sustained inflammation.