What Is Inflammation's Role in Chronic Disease?

Inflammation was once understood almost exclusively in terms of its protective role — the redness, swelling, heat, and pain of an infected wound or a sprained ankle, signaling that the immune system is fighting and healing. That understanding remains accurate but incomplete. Over the past three decades, a broader picture has emerged: chronic, low-grade, systemic inflammation — often without any obvious site of infection or injury — plays a central role in the development and progression of virtually every major chronic disease of modern life: cardiovascular disease, type 2 diabetes, obesity, Alzheimer's disease, cancer, depression, and more.

Acute Inflammation: The Protective Response

Acute inflammation is the immediate, short-lived response to tissue injury or pathogen invasion. It is mediated by the innate immune system and proceeds through well-characterized steps:

1. Tissue damage or pathogen recognition triggers the release of inflammatory mediators from local cells: histamine from mast cells, bradykinin from plasma proteins, prostaglandins and leukotrienes from arachidonic acid metabolism, cytokines (TNF-α, IL-1β, IL-6) from macrophages.