Veterinary Immunology and Serology

ACTIVE RECRUITMENT OF INFLAMMATORY CELLS AT THE SITE OF INFECTION

• Neutrophils and monocytes are normally present in blood are recruited to the site of infection by binding to adhesion molecules on endothelial cells under influence of chemo attractants produced in response to infection e.g. complement factor C5a, fibrino peptide B, platelet factor 4 etc.
• The chemotactic molecules diffuse from the site of tissue damage and form a concentration gradient.
• Neutrophils move towards the area of highest concentration i.e. the area of tissue damage. Inflammation is an important process for the recruitment of cells to the site of infection.
• Next there is adherence of circulating leukocytes to the site of infection through a multiple processes involving attachment of cells to endothelium and migration through the endothelium.
• The endothelial cells express the adhesion molecules, which are triggered by bacterial products like lipopolysaccharide or the factors (cytokines, chemokines and vesoreactive factors) released by damaged tissues or resident tissue macrophages.
• These adhesion molecules bind neutrophils and lymphocytes. The neutrophils do not bind tightly but lose their flow speed and roll over the endothelial cell surface and finally escape into tissues by diapedesis.
• Some important vasoreactive molecules produced during inflammation are hitamine, serotonin, kinins (bradykinin etc.) and they play important role in inflammation.
• During inflammation, first neutrophils and later monocytes followed by lymphocyte and thrombocytes (platelets) accumulate around the infectious organism.