مدرس المادة
- The first line of defense includes some physical and chemical barriers such as epithelial cell layers of the skin, mucosal tissues (e.g., gastrointestinal, respiratory, and urogenital tracts), and glandular tissues (e.g., salivary, lacrimal, and mammary glands).
- If an infectious agent overcomes the physical and chemical barriers, cellular immune responses are rapidly activated, which constitute the second line ofdefense, are triggeredby cell surfaceor intracellular receptors that recognize components of pathogens.
- Some white blood cell types are activated to rapidly engulf and destroy extracellular microbes through the process of phagocytosis.
- Also, many cells are activated through their receptors to produce a variety of antimicrobial substances that kill pathogens, as well as cytokine and chemokine proteins that recruit cells, molecules, and fluid to the site of infection, leading to swelling and other symptoms collectively known as inflammation.
- Also, contribute dendritic cells that carry and present pathogens to lymphocytes to the activation of adaptive immune responses, the third line of defense.
تحميل الملف