HP - Immune System Notes PDF

The Immune System: Innate & Adaptive Immunity Lecture Outline -Immune System: Main Function -Key Players -Tissues -Cells of the Immune System -Innate Immunity -Adaptive Immunity The Immune System -The primary function of the immune system is to find and kill invasive microbes, primar...

The Immune System: Innate & Adaptive Immunity Lecture Outline -Immune System: Main Function -Key Players -Tissues -Cells of the Immune System -Innate Immunity -Adaptive Immunity The Immune System -The primary function of the immune system is to find and kill invasive microbes, primarily: -Bacteria -Fungi -Viruses -Parasites -The body’s first line of defense against microbial attack IS NOT the immune system, but a set of barriers that keep pathogenic microbes from gaining access to human tissue. -Human skin -Acidity of the stomach lining -Flow of urine down the urethra -Low pH of the female reproductive tract -The immune system differentiates between self and non-self by using proteins and carbohydrates on the cell surface as antigens: any substance (usually large proteins) that initiates an immune system response (virulence), often found on the surfaces of bacteria and viruses -The immune system works through two separate but overlapping responses: -Innate responses are not directed against a particular invader. -They work in the same way, regardless of the invader. -Adaptive responses are directed against particular pathogens and foreign invaders. -Rely on immune memory, which gives rise to long-term resistance, or protective immunity, against a specific foreign substance or invader (antigen). -further divided into humoral immunity (antibody-mediated) cellular immunity (T cells-mediated) Key Players Tissues of the Immune System -Central Lymphoid Tissues -Bone Marrow -Differentiation of hematopoietic stem cells into all cell types except mature T cells -Maturation & selection of B cell progenitors resulting in naïve B cells that recognize foreign antigen and can distinguish between self and nonself -Thymus -Maturation & selection of precursor T cells resulting in naïve T cells that recognize foreign antigen and can distinguish between self and nonself -Thymic tissue enlarges during childhood but after puberty it atrophies and is replaced by fat, however it continues to function to some extent throughout life -Peripheral Lymphoid Tissues -Lymph nodes -Located where lymph channels converge -Cells and antigen flow slowly through highly organized node allowing T cells, B cells, macrophages, and dendritic cells to interact -Spleen  -Filters antigen from the blood -WBC interact in white pulp similar to LN -Red pulp consists of small sinusoids that trap old/damaged RBCs and cause their lysis, macrophages remove old/damaged RBCs and any cell debris -Lymph Nodules -Mucosa-associated lymphoid tissues (MALT) -Tonsils -Appendix -Peyers patches (GALT), etc. -Nodule has epithelial covering with specialized phagocytic epithelial cells (M cells) that transfer antigen into the lymphoid tissue -Secrete IgA onto mucosal surface – initiates inflammatory reaction and prevents microbial binding to surface Cells of the Immune System -Derived from the hematopoietic stem cells in the bone marrow -Hematopoietic stem cells differentiate into myeloid and lymphoid lineages -Myeloid lineage cells include the granular phagocytic leukocytes (monocytes/macrophages, granulocytes, and dendritic cells) and all other non-lymphoid blood cells -Lymphoid cells include small lymphocytes (B and T cells) and the larger granular natural killer cells (NK cells) Leukocytes Monocytes/Macrophages -Monocytes circulate in blood for ~1 day (2-8% of WBC) and are the largest leukocyte. -Monocytes mature into macrophages when they migrate into the tissues and acquire greater phagocytic ability -Macrophages -Engulf and kill invading microorganisms and infected cells, clean up dead cells and cellular debris -Help induce/maintain inflammation by secreting signaling proteins (cytokines) to activate and recruit other immune cells Neutrophils -Primary role is phagocytosis of bacterial invaders -Most abundant leukocytes (50-70% of WBC) -1st to arrive at the site of acute inflammation- can form pseudopods and are highly mobile -Engulf & destroy bacterial invaders using degradative enzymes (lysozymes) and antimicrobial substances in their cytoplasmic granules, including H 2O2 and NO Eosinophils -1-3% of WBC -Kills parasitic worms -Recruited to sites of acute inflammation -Longer life span than neutrophils -Involved in chronic inflammation -Granules contain digestive enzymes, lysozyme, peroxidase, & inflammatory chemicals -Key component of allergic asthma & other allergic reactions Basophils -