Inflammation: Immune Response to Tissue Injury or Infection

Inflammation is a local immune response to tissue injury or infection, characterized by heat, redness, edema, pain, and loss of function. It begins with vasoconstriction to reduce blood loss and clot formation.

Injured cells release vasoactive chemicals like prostaglandins and histamine, causing vasodilation and increased blood flow. These chemicals also increase capillary permeability, allowing fluids and proteins to leak into the tissue.

Chemotaxis is a multi-stage process where circulating immune cells called neutrophils move to the injury site. Chemoattractants released by injured cells cause neutrophils to stick to endothelial cells. Neutrophils then squeeze through endothelial gaps in a process called diapedesis.

Upon arrival, neutrophils engulf and digest bacteria through phagocytosis. After pathogen destruction and waste removal, tissue repair begins. Locally produced growth factors stimulate fibroblasts to divide and secrete collagen, reinforcing the wound.

Anti-inflammatory drugs, such as non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen, inhibit inflammation by blocking the production of inflammatory chemicals. They target cyclooxygenase (Cox) to reduce prostaglandins and other inflammatory chemicals, thereby reducing vasodilation, edema, and pain.