Question

describe the events involved in initiation of an inflammatory reaction. Include changes in vascular permeability and the causative agent's involved. Also include mechanisms by which inflammatory cells are recruited to the site of injury or infection

Answer 1

Inflammation is a local immune response produced by the cells towards the presence of any pathogenic or foreign body. The four signs and symptoms of inflammation are,

· Redness (rubor)

· Edema or swelling (tumor)

· Pain (dolor)

· Heat (calor)

The excessive blood flow to the inflamed area and stimulation of nociceptors due to compression causes redness, pain and heat. Increased vascular permeability causes edema. Inflammation helps to prevent the spread of infections and injuries to other regions of body.

The signs of red, hot and inflammation at the site of surgery indicated post-operative infection, identified by inflammation.

Events occurring during inflammation include,

1. Injury or immediate reactions: Vasoconstriction occurs, blood clots are formed, inflammatory mediators such as the chemokines and cytokines are released by the mast cells into the inured area.

2. Vascular reactions: The blood vessels located in the nearby region dilate, vascular permeability increases, fluid exudate forms

3. Edema or formation of pus: The fluid accumulates to form edema. Neutrophils infiltrate to the region to form pus.

4. Resolution or scar formation: Macrophages, lymphocytes, and fibroblasts migrate to the inflammation site, the injury is repaired by initiating the immune response. After injury repair, scar is formed.

Mechanism of movement of neutrophiles (and other leukocytes) to the site of inflammation:

During the inflammatory response, the damaged cells release the chemicals that attract white blood cells towards the affected site. This process is known as “chemotaxis. The escape of white blood cells from the circulation is known as “diapedesis.”

Positive chemotaxis is the movement of bacteria towards the higher chemical concentration (chemoattractants), and the negative chemotaxis is the movement of bacteria in opposite direction to the chemical (chemorepellents).

The escape of neutrophils from the circulation by squeezing through the blood vessels is known as “diapedesis.” The neutrophils move to the site of inflammation by ameboid movement.