ABSTRACT
The rapid local and systemic changes occurring after challenge are collectively called the acute phase response, and events which continue to cause acute challenges may lead to prolonged changes associated with chronic inflammation. Histologically, local tissue acute inflammation involves the presence of intravascular platelet aggregation, extra-vascular accumulation of fluid and plasma components, and the accumulation of polymorphonuclear leukocytes (PMN) within the tissue. The mononuclear phagocyte, comprising the tissue macrophage and peripheral blood monocyte populations, are most aptly placed in the tissues to encounter pathogens and initiate the acute response. Nutrophil accumulation and stromal cell activation follow through release of arachidonate metabolites and cytokines and while PMN accumulation is a prominent feature of the acute phase response, platelets and mononuclear phagocytes are likely the most important initiators of the response. Tumor necrosis factor, is also released from mononuclear phagocytes and from mast cells, and elicits many overlapping responses as does IL-1.
