In response to foreign or self-antigens, the tissue immune cells such as macrophages and dendritic cells release cytokines such as IL-1 and TNF-α. These cytokines induce the injury-site-endothelial cells to release Selectins and Integrins which stimulate chemotaxis and diapedesis of the circulating leukocytes.
Thus the hallmarks of chronic inflammation are the infiltration of the primary inflammatory cells such as macrophages, lymphocytes, and plasma cells in the tissue site, producing inflammatory cytokines, growth factors, enzymes and hence contributing to the progression of tissue damage and secondary repair including fibrosis and granuloma formation, etc. However, the composition of the white blood cells changes soon and the macrophages and lymphocytes begin to replace short-lived neutrophils. Most of the features of acute inflammation continue as the inflammation becomes chronic, including the expansion of blood vessels (vasodilation), increase in blood flow, capillary permeability and migration of neutrophils into the infected tissue through the capillary wall (diapedesis).
