Acquired Immunity Cells are initially and require before they can work Responds to individual microbes

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1 1 of 10 THE IMMUNE SYSTEM CHAPTER 43; PAGES WHY DO WE NEED AN IMMUNE SYSTEM? It s a dirty, dirty world out there and we are vastly outnumbered Bacteria and parasites are everywhere The body has cells bacteria live on our skin bacteria (~600 species) live in our guts! Most bacteria are normally harmless but if given the chance, THE DOUBLE-EDGED SWORD Some is inevitable in most instances when the immune system is activated Bacteria and parasites have evolved ways to,, or the immune system Some can make the immune system work against the host A fine balance between TYPES OF IMMUNITY Innate immunity Constantly and prepared for infection Responds to a range of microbes exactly the Acquired Immunity Cells are initially and require before they can work Responds to individual microbes

2 2 of 10 INNATE VS. ACQUIRED IMMUNITY Innate Immunity of defence working immediately Requires no education Antigen- Works the same for every invader Resistance is improved by repeated exposure to the same infectious agent Acquired Immunity Works after a Requires the cells involved learn about the invader Antigen- Resistance improved by repeated exposure to the infectious agent Cells The phagocytes Neutrophils Eosinophils Macrophages A lymphocyte Natural Killer cells INNATE IMMUNE SYSTEM PLAYERS Soluble factors Complement THE PHAGOCYTES White blood cells that are designed to The foreign particle is contained within a Other organelles contain enzymes and antimicrobial molecules Fusion of phagosome with lysosome Combine foreign particle with enzymes to of degraded material

3 3 of 10 NEUTROPHILS The major phagocytic immune cell ~ % of all white blood cells Granules contain enzymes to engulfed particles Very easy to recognize with their multi-lobed nuclei Neutrophils are usually the first cell type to a site of infection Important in defence against extracellular microorganisms Many like Staphylococcus or Escherichia coli EOSINOPHILS Phagocytic cells related to neutrophils Make up about % of the WBCs Granules contain enzymes to breakdown particles Specialized for large parasites like Can t engulf the worms, but adhere to & form a on their surface Hydrolytic enzymes are into the pocket to attack the worm MACROPHAGES Highly phagocytic cells dispersed the body tissue but are not found in the blood Are very long lived cells that develop from monocytes They have many different jobs Remove (dead cells, foreign bodies, etc.) from the tissues A component of the immune response Digest foreign material and (pieces) to the T-cells This can activate the immune response More later Different organs have distinct, permanent populations Liver, lungs, brain,

4 4 of 10 NATURAL KILLER CELLS A special type of lymphocyte We ll talk about others later NK cells have the ability to recognize Infected with a These cells express different proteins on their surface Once recognized, the NK Cell removes them Causes them to die by COMPLEMENT The complement system consists of over 30 different proteins The main function of complement is the of & Other functions include: Activation of inflammation Opsonization of bacteria Immune clearance We ll talk more of these with regards to COMPLEMENT ACTIVATION Once activated, the complement cascade causes the formation of the (MAC) The MAC forms a in the membrane of the target cell freely moves into the target cell and causes THE INFLAMMATORY PROCESS Invading organisms or tissue damage initiate a complex cascade called Anything that ends in -itis

5 5 of 10 The Cardinal signs of inflammation are: Rubor Tumor Calor Dolor Functio laesa Caused by and at the site of inflammation Vasodilation leads to redness and heat Edema (fluid leaving the vasculature) gives rise to swelling, pain and loss of function INFLAMMATION 1. initiate the inflammatory response Signals from the Signals from other and injured tissue 2. Detected by and leads to the release of vasodilation Vasodilation lets more 3. The chemical signals released tell the neutrophils to 4. Once at the site of infection, neutrophils kill the bacteria by 5. After the bacteria are gone, we need to 6. Resident phagocytose the neutrophils and clean up the site of injury This response is a local response, working only at the site of infection

6 6 of 10 ACQUIRED IMMUNE SYSTEM PLAYERS Cells Soluble Factors The Lymphocytes Antibodies T-lymphocytes Cytokines Helper Cytotoxic B-lymphocytes Plasma cells The phagocytes Dendritic cells Macrophages ACQUIRED IMMUNE SPECIFICITY The acquired immune responses are to a given invading pathogen How? All pathogens have proteins capable of eliciting an immune response (= ) After phagocytosis by a dendritic cell or, these antigens are presented on a surface protein (MHC) class II (APC) Helper recognize the specific antigen and respond accordingly Alternatively, altered self-cells also possess, antigens antigens antigens All cells present antigens on MHC molecules Normal self and any altered antigens An APC, but more appropriately called a Cytotoxic recognize these antigens and respond accordingly of the target cell

7 7 of 10 MHC RECOGNITION In order for a T-cell to respond to an antigen it must be on an MHC molecule A surface protein on the T-cell interacts with the Ag MHC complex The ( ) Every T-cell has a TCR capable of binding a single antigen Made at You have T-cells that bind to antigens you have never even seen! Over possible TCRs + mutations! HELPER T-LYMPHOCYTES Upon activation, they secrete chemical messages Drive and the specific immune response Depending on the antigen presented, the helper T-cell directs 1 of 2 responses Activation of Making these cells better killers = immunity Activation of Induces antibody production = immunity B-LYMPHOCYTES Just as T-cells have a unique surface receptor B-cells also have a surface receptor, the ( ) Surface antibody molecule capable of recognizing a antigen Like T-cells, these BCRs are made at before ever seeing the antigen they bind to! Over possibilities + mutations!

8 8 of 10 CLONAL SELECTION Out of the millions of B-cells you have in circulation, only will become activated upon exposure to a antigen of the specific antigen Like enzymes and substrates Expansion of the cell All daughters remain genetically identical Plasma and memory cells T-cells also undergo clonal expansion Two possible options: B-CELL DIFFERENTIATION cells Produce large amounts of Multiple functions cells Go into circulation and until the antigen is encountered Can live over 30 years! IMMUNE MEMORY Upon activation, both T-cells and B-cells differentiate into what are called The phenomenon is immune memory Immune Memory is important upon to a encountered antigen The initial response of a immune system to any antigen takes time for the machinery to start working This is the immune response Normally delayed about The immune system about the new antigen

9 9 of 10 During the primary immune response, lymphocytes proliferate and differentiate The end result is: A memory cells A number of plasma cells Only a few plasma cells means longer time to 7-14 days Upon exposure, the memory cells expand much More cells at the beginning means more cells at the More cells means more Response occurs within Degree of response is also A antigen (B) elicits a response VACCINATION Immune memory is why vaccination works Naturally, you develop immune memory to you have encountered These pathogen may have made you very sick Afterwards, you become Vaccines are designed to the pathogen Your immune system thinks it is real and develops a But the vaccine is engineered so that it If you then encounter the real pathogen, you can mount a quick ANTIBODIES The soluble mediator of the adaptive immune system Also called When a B-cell becomes a plasma cell, it starts producing its BCR in a form that can Basically, there are 2 ends of an antibody The region The antigen binding sites

10 10 of 10 The region Recognized by other immune cells There are 5 classes of antibodies Slightly different constant regions and functions for each ANTIBODY FUNCTIONS The main purpose of antibodies is to inactivate antigens through binding of a pathogen receptor of a bacterium of soluble proteins Ultimately leads to activation Ultimately leads to Regardless of the mechanism, the result is RECOGNITION OF SELF Remember that TCRs and BCRs are all made There are billions of potential foreign antigens out there What are the changes a TCR or BCR is made that reacts with a? It happens Recall that recognition of an antigen leads to an What if one of our B-cells reacts to a self-antigen? Your immune system fights Can you see a problem here? During the maturation of both T-cells and B-cells, they are given a They are shown If they the self-antigen they fail the test If they fail the test they are This leaves T-cells and B-cells that react to