The Immune System is the Third Line of

The Immune System is the Third Line of Defense Against Infection

Phagocytic Cells • Phagocytes attach to their prey via surface receptors – And engulf them, forming a vacuole that fuses with a lysosome 1 Pseudopodia surround microbes. Microbes 2 Microbes are engulfed into cell. MACROPHAGE Vacuole Lysosome containing enzymes 3 Vacuole containing microbes forms. 4 Vacuole and lysosome fuse. Toxic 5 compounds and lysosomal enzymes destroy microbes. 6 Microbial debris is released by exocytosis.

Phagocytosis

• The lymphatic system – Plays an active role in defending the body from pathogens 1 Interstitial fluid bathing the tissues, along with the white blood cells in it, continually enters lymphatic capillaries. Interstitial fluid Adenoid Lymphatic capillary 2 Fluid inside the lymphatic capillaries, called lymph, flows through lymphatic vessels throughout the body. Tonsil 4 Lymphatic vessels return lymph to the blood via two large ducts that drain into veins near the shoulders. Lymph nodes Spleen Peyer’s patches (small intestine) Blood capillary Tissue cells Lymphatic vessel Appendix Lymphatic vessels Figure 43. 5 Lymph node Masses of lymphocytes and macrophages 3 Within lymph nodes, microbes and foreign particles present in the circulating lymph encounter macrophages, dendritic cells, and lymphocytes, which carry out various defensive actions.

Antibodies are Produced by B Lymphocytes

• Major events in the local inflammatory response Blood clot Pin Pathogen Macrophage Chemical signals Phagocytic cells Blood clotting elements Phagocytosis Capillary Red blood cell 1 Chemical signals released by activated macrophages and mast cells at the injury site cause nearby capillaries to widen and become more permeable. 2 Fluid, antimicrobial proteins, and clotting elements move from the blood to the site. Clotting begins. 3 Chemokines released by various kinds of cells attract more phagocytic cells from the blood to the injury site. 4 Neutrophils and macrophages phagocytose pathogens and cell debris at the site, and the tissue heals.

ANATOMY OF THE IMMUNE SYSTEM

Epitopes: Antigen Regions that Interact with Antibodies

Bakteri dan virus membawa senyawa kimia di permukaannya, yang disebut antigen. Sebagian limfosit menghasilkan antibodi untuk mengikatkan diri dengan antigen, sehingga memudahkan sel darah putih menelan bakteri tersebut. Antibodi mempunyai ciri khas yang sangat berbeda dan mereka hanya dihasilkan untuk dan mengikatkan diri kepada antigen khusus.

Imunoglobulin atau antibodi adalah sekelompok glikoprotein yang terdapat dalam serum. terdiri dari 82 -96% polipeptida dan 4 -18% karbohidrat. Struktur dasar imunoglobulin terdiri atas 2 macam rantai polipeptida yang tersusun dari rangkaian asam amino yang dikenal sebagai rantai H (rantai berat) dengan berat molekul 55. 000 dan rantai L (rantai ringan) dengan berat molekul 22. 000. Tiap rantai dasar imunoglobulin (satu unit) terdiri dari 2 rantai H dan 2 rantai L, diikat oleh suatu ikatan disulfida.

q. Immunoglobulins are a group of proteins (gamma globulins) produced by the body from B lymphocytes and plasma cells in response to presence of foreign bodies.

Quiz 1. Explain the difference between: a) Innate Immunity and Adaptive (acquired) Immunity. (10 points) b) T cells and B cells. (6 points) 2. Distinguish among the roles of the Ig. A, Ig. G, Ig. M, Ig. E ! (4 points)