Acute and Chronic Inflammation: Mechanisms and Health Impact

 

Introduction of inflammation

Inflammation is a protective response intended to eliminate the initial cause of cell injury as well as  necrotic cells and tissues resulting from the original  insult. Inflammation (latin , inflamatio , to set  on fire ) is a localized protective response  elicited by injury or destruction of tissues,  which serves to destroy, dilute both the injurious agent and  the injured tissue. Inflammation can be acute, which develops rapidly and lasts for a short time, or chronic, which persists for longer periods and may lead to tissue damage. The process is characterized by classical signs such as redness, heat, swelling, pain, and loss of function, which result from increased blood flow and the movement of immune cells to the affected area. While inflammation is essential for defense and repair, uncontrolled or prolonged inflammation can contribute to various diseases, including arthritis, cardiovascular disorders, and autoimmune conditions. Body defense reaction- eliminate or limit the spread of injurious agent. Is a protective response. Inflammation is a local response of living mammalian tissues to injury due to any agent.

 Types of inflammation

1. Acute inflammation

Acute inflammation is the body’s immediate and early response to injury or infection, designed to protect and restore tissue. It develops rapidly and usually lasts for a short period, ranging from a few hours to a few days. The main purpose of acute inflammation is to eliminate harmful agents, remove damaged cells, and initiate the healing process. It is typically characterized by redness, heat, swelling, pain, and sometimes temporary loss of function, all caused by increased blood flow and the movement of immune cells to the affected site. Unlike chronic inflammation, which can cause long-term damage, acute inflammation is usually beneficial and resolves once the cause of injury is removed, leaving behind repaired and healthy tissue. Acute inflammation is a Short duration and Represents the early body reaction-followed by healing.

2. Chronic inflammation

Inflammation of prolonged duration (weeks or months) in which active inflammation, tissue destruction, and attempts at repair are proceeding simultaneously. Characterized by the following: Chronic inflammatory cell infiltration lymphocytes, plasma cells and macrophage, Tissue destruction by inflammatory cells, and Healing and Repair – involving New Blood v e s s e l   proliferation (Angiogenesis) and Fibrosis. It is often associated with ongoing tissue damage and repair happening at the same time, leading to scarring or loss of normal function. Chronic inflammation may result from persistent infections, long-term exposure to irritants, or autoimmune reactions in which the body mistakenly attacks its own tissues. It is commonly linked to diseases such as rheumatoid arthritis, tuberculosis, inflammatory bowel disease, and even conditions like cancer, diabetes, and heart disease. While it serves as a continuous attempt by the body to defend and heal, uncontrolled chronic inflammation can harm organs and contribute to serious health problems over time. Chronic Inflammation it is the inflammation of a prolonged duration (weeks, months, to years) in which active inflammation, tissue injury,  healing process, proceed simultaneously. Inflammation of slow progress and marked chiefly  by the formation of new connective tissue.

Signs of Inflammation

• Heat (calor)

• Redness (rubor)

• Swelling  (tumor)

• Pain (dolor)

• Loss of function

What is a systemic manifestations?

• fever (irritation of centre of thermoregulation), TNF, IL-1, and IL-6 – high erythrocyte sedimentation rate.

• leucocytosis - increased number of WBC: bacteria – neutrophils, parasites – eosinophils, viruses - lymphocytosis

• leucopenia - decreased number of WBC: viral infections, salmonella infections, rickettsiosis

• immunologic reactions - increased level of some substances (C-reactive protein).

Causes of inflammation

Infective agents like bacteria, viruses and fungi etc, Immunological agents cell medicated and antigen antibody reactions, Physical agents heat, cold, and radiation, Chemical agents organic and inorganic poisons, and Inert materials such as foreign bodies. 

1. Persistent infections:

Infectious organisms in regions where they are protected from host defenses e.g. undrained abscess in bone marrow, empyema thoracis,  Resistance of infective agent to phagocytosis & intracellular killing e.g. tuberculosis, leprosy, viral infection,  fungal, etc  => Granuloma.

2. Immune mediated inflammatory diseases:

Autoimmune diseases e.g. Hashimoto’s thyroiditis, rheumatoid arthritis, systemic lupus erythematosis, multiple sclerosis, Allergic diseases: bronchial asthma and inflammatory bowel disease (IBD).

3. Prolonged exposure to potentially toxic agents:

Prolonged exposure to potentially toxic agents that cannot be removed by enzymatic breakdown or phagocytosis, either exogenous (silica, asbestos fibers, foreign body, keratin) or endogenous (uric acid, necrotic tissue). 

Acute inflammation has two main components

Vascular Changes : Alteration in the vessel caliber  resulting in increased blood flow (vasodilation) and  structural changes that permits plasma proteins to  leave circulation (increased vascular permeability). Cellular Events : Emigration of leukocytes from the  microcirculation and accumulation in the focus of injury (cell recruitment and activation ). 

 Conclusion

Inflammation is a vital protective response of the body to injury, infection, or tissue damage. It helps eliminate harmful agents, remove dead cells, and initiate tissue repair. However, while acute inflammation is beneficial and short-term, chronic inflammation can lead to tissue damage and contribute to many diseases. Therefore, proper regulation of inflammation is essential for maintaining health and preventing long-term complications.