VPB 121: Veterinary Physiology - II (2+1)

EFFECT OF ALVEOLAR MACROPHAGES

• It is the first line of defense
• In the lungs, macrophages are in the alveolar lining fluid
• Surfactant proteins, complement proteins, opsonins and lysozymes in the respiratory secretions assist in the phagocytosis of particles like bacteria.
• Some of the destroyed particles are removed by microciliary system. Others cross the alveolar wall and enter into the lymphoid tissues of the airways.
• Lung’s immune response of the functioning macrophages viz antigen presenting cells
• Hypoxia depressed the macrophage activity
• Endogenous glucocorticoids/synthetic corticoids suppresses macrophages activity
• Excessive administration of synthetic corticoids causes increased susceptibility to bacterial infection in the lung
• Animals transported to a longer distance show stress induced macrophage dysfunction
• Viral infection decreased macrophage functions and contributes the secondary bacterial infection.

Effect of other WBCs

• Neutrophils are also involved in the phagocytosis of inhaled particles
• The invaded bacteria is destroyed by the release of toxic oxygen radicals and proteolytic enzymes
• The free radicals also damage the lung tissues also; Antioxidants and protease inhibitors protect the lung tissue from this effect.

Role of cytokinines and chemokinines

• Cytokinines and chemokinines are proteins released by the macrophages, lymphocytes, epithelial cells during inflammatory process in response to lung injury by infectious agents, allergy or inhalation of toxic gases.
• These proteins attract the inflammatory cells (Neutrophils) to the site of injury and provide communication between neutrophils during inflammatory process.
• These proteins are also involved in tissue remodeling and healing process
• They act as a potent chemo attractant of the inflammatory cells (Neutophils) and produce agents for prolonged inflammatory response