Understanding the Immune System: Overview & Defense Mechanisms

1. The Immune System • Overview • Systems involved • Cells involved • Non-specific Immunity • Specific Immunity • Antibodies • Complement • Immunology Tutorial

2. Host defense mechanisms • First line of defense: host ____________ and chemical barriers (skin, mucous, tears, etc.) • Second line of defense: phagocytes and ______________________ (non-specific) • Third line of defense: __________________ immune reactions

4. Systems involved in immune defenses • 1) Bloodstream • 2) Lymphatic system • 3) Reticuloendothelial (or mononuclear phagocyte) system -- support system of _____________________ tissue fibers and endothelium • 4) Extracellular fluid

5. Communicating systems

6. Communicating systems

7. Important blood cells involved in immune systems • Stem cells -- undifferentiated cells which give rise to all the others. Found in __________ ____________. Produce erythrocytes (RBCs), leukocytes (WBCs), and platelets • Leukocytes are generally divided into 2 groups: granulocytes (polymorphonuclear __________________) and agranulocytes (mononuclear leukocytes) • Examples of granulocytes: neutrophils (“microphage”), basophils, eosinophils • Examples of agranulocytes: monocytes, lymphocytes

8. Granular leukocytes Erythrocytes Agranular leukocyte

9. Agranulocytes • Lymphocytes • _____________ -- derived from the thymus. Important in cell-mediated immunity. • _____________ -- derived from bone marrow, primarily. Important in humoral immunity. • Monocytes -- large, common, important in ____________________ and specific immune functions. Non-circulatory (tissue-associated) monocytes are known as macrophages.

10. Lymphocyte: note_____________ nucleus, little cytoplasm. Is smaller than monocyte

11. Monocyte: note unlobed, rounded nucleus and apparent lack of granules Neutrophil (a granular leukocyte): note granules and ___________ nucleus

15. Non-Specific Immune Reactions • Inflammation • Phagocytosis (and presentation) • Complement

16. “Rubor” -- __________ • “Calor” -- warmth • “Tumor” -- ____________ • “Dolor” -- pain

18. Non-specific Immunity: Phagocytosis • Carried out primarily by neutrophils and by monocytes/macrophages (collectively called ‘_______________’)

19. The scanning electron micrograph above, shows a human macrophage (gray) approaching a Streptococcus pyogenes (yellow). Riding atop the macrophage is a spherical lymphocyte. Both macrophages and lymphocytes can be found near an infection, and the interaction between these cells is important in eliminating infection.

20. Phagocytosis by Macrophages

22. Phagocytic killing Phagocytes shift from aerobic to ___________________ metabolism. Leads to drop in _________, which activates lysosomal enzymes.

23. Oxygen-dependent phagocytic killing

24. Phagocyte failure • Pathogens can neutralize phagocyte products: • _____________________ produces carotenoids which quench singlet oxygen • Mycobacterium sp. can grow within macrophages using glycolipids in their cells walls to scavenge toxic _________________ species • Strep. pyogenes and Staph. aureus produce leukocidins which destroy ________________.

25. IgG Specific Immunity: Antibodies or Immunoglobulins

27. The complement system • “Complement” is an additional mechanism that is brought into play at several levels in _______ __________. • Is a cascade of proteins which result in membrane permeation and cell death

29. The Complement System: a Summary