Adaptive Immunity PDF

THE ADAPTIVE IMMUNITY Wednesday, October 18, 2023 12:43 PM ADAPTIVE IMMMUNITY → Two classes of adaptive immunity: 1. Antibody mediated or humoral immunity - Involves production of antibodies by B lymphocycres derivatives knows as plasma cells - Produce by a cell t...

THE ADAPTIVE IMMUNITY Wednesday, October 18, 2023 12:43 PM ADAPTIVE IMMMUNITY → Two classes of adaptive immunity: 1. Antibody mediated or humoral immunity - Involves production of antibodies by B lymphocycres derivatives knows as plasma cells - Produce by a cell that goes act somewhere else - Not a direct cell-to-cell action - Mediated by antibodies (by B lymphocytes) ○ Become plasma cells than make a lot of antibodies □ Antibodies will get released into the blood and eventually circulate to the site of infection □ Stay in the lymph tissue, don't go to site 2. Cell-mediated immunity - Involves production of activated T lymphocytes ○ Directly attack unwanted cells - 2 types 1. T cells comes to an infected cell and kill the cell, is precise and lethal (happens within seconds): releases a chemical that will kill everything 2. The general-command cells ○ Gives instructions, tell other immune cells what to do and how to do it ○ B cells don't know what antibodies to make, how to make it better or when to make it without a T cell to give it instructions ○ Macrophages become superhero macrophages when given instructions by T cells ○ HIV from before led to complete immune deficiency bc they would kill T cells, the generals → Antigen: - Large, foreign, unique complex molecule → Colour is there to describe the different antigen receptors that see specific molecules - Includes 9elicits) an immune response against itself → One cell has over a thousand receptors for just 1 antigen - In general, the more complex a molecule is, the greater its antigenicity ( the ability to reduce an immune response) § Antigenicity: is not a yes or no, there's a spectrum § Highly antigenic: A, B, D antigen § Less antigenic: fisher system - Most protein in nature ->most antigenic FUNCTIONS OF ADAPTIVE IMMUNITY → Specificity -> billions of lymphocytes recognizing different antigens - Form memory T/B cells -> all macrophages have the same set of receptors but B/T cells have different receptors that see different antigens → Lymphocytes with receptors that recognize the specific antigen will proliferate (clonal expansion of clonal selection) → Wait to be infected before cloning it - Clonal expansion: only the ones that can see the antigen or engage the antigen, the receptor is going to send a signal → We don’t want to many of them so we only make 1 randomly of each but since that to the cell to start dividing -> clone and expand that clone single one can't fight the whole infection alone, we close it - Clonal selection: only cells of the B/T cell can recognize the antigen that we are exposed to will be selected, each will → Only cells whose receptors are targets will be cloned be called cloned bc they will have different receptors on it - Every time we make a new B cell it will be generated in the bone marrow or thymus, it will be a different receptor → The adaptive immune system acquires immunological memory towards foreign antigens -> acquired or protective immunity - Acquired only when we see the pathogen or get vaccinated - Immunological memory means we will set aside some of those cells during the fight against a pathogen and call them memory B/T cells that will be used for the next time we get infected by the same antigen b/c they will be trained and be activated much faster = better immune response Not in the fight - sideline characters B LYMPHCOYTES → Secreted antibodies aka mediators of humoral immunity → Membrane bound on B cells surface ->function as antigen receptors -> initiate B cell activation proliferation and differentiation of antigen-specific B cells -> plasma cells -> secretion of soluble form of the antibody (same specificity as the mb bound Picture Description: ○ The receptors on the B cell is called an immunoglobulin ○ When B cells become plasma cells it will make a secreted version of that receptor = the Golgi body doesn't anchor it to the membrane - The secreted receptor exits the cell through a vesicle BASIC FUCNTIONS OF ANTIBODIES Picture Description: → Binding antigens ○ A antibody has 4 chains → The Fc (fragment, crystallizable) on an antibody gives it functions: ○ 2 identical pairs → (1) Activate complement system ○ 1 is heavy (long) → (2) neutralization: antibody that can bind to the virus first and prevent it from entering a cell, will coat it ○ 1 is light (short) - Binding and neutralizing bacteria ○ The Fab is where it recognizes the antigen - Make neutralizing antibodies that will bind to the toxin as soon as it's released and not allow the toxin to kill our ○ Stands for fragment antigen binding cells - Inhibiting viral entry into host cells → (3) enhancing phagocytosis of pathogens (opsonization) - Compliment: coat pathogen to allow phagocytosis to occur better - Opsonization (activate phagocytosis) and compliment activation (innate proteins) = innate but also a slow process T LYMPHOCYTES → Can only see peptides of pathogens → Carry out cell-mediated immunity → Do not secrete antibodies; directly bind to targets → Killer T cells release chemicals (granules) that destroy (insert) targeted cells (in seconds) - Engage receptors in the cell to make cell death, apoptosis programed cell death - Strong signal → Clonal and antigen specific; acquire receptors / mature in the thymus (sits on top of the heart) → T cells are activated for foreign attack only when the attack is on the surface of a cell that carries foreign antigens presented on self-antigens Picture Description: ○ A T-cell receptor (TCR) ○ Has 2 chains, equal in size ○ Can't see directly, needs dendritic cells to present through our own proteins, the dendritic cell will use its own protein to show the antigen to the T cell T CELLS AND IRS TARGETS → T-cell receptor (antigen receptor) -> peptide fragments (antigen) bound to self proteins called Major Histocompatibility Complex ((MHC) -> displayed on surface of APCs (antigen presenting cells / dendritic cells) → 2 phases of T cell functions: 1. Inactive / naïve state: sitting in an inactive state The MHC protein - Dendritic ell needs to activate it on the APC will - Even if it sees a pathogen it can't do anything bc its inactive carry the - Activation occurs in the lymph tissue / nodes peptide - If T cell recognizes antigen it clones pathogen and - If T cell doesn't recognize the antigen it leaves pass it t the TCR - There needs to be a "check and balance" which is on the ○ Only want to activate cell when it NEEDS to surface of the T ○ We don't want the T cells to destroy healthy cells cell ○ Are very powerful 2. Active T cells: - The clones will leave the lymph nodes and go to the site of infection and start attacking infected cells ○ They kill infected cells cb infected cells will also be presenting the antigen on its surface TWO TYPES OF T CELLS → CD4 cells (mostly helper T cells: Th) ○ CD4 is differentiate from other T cells (ID)complex ○ Plays a role in recognition of MHC ○ These are the generals who command the rest of the immune cells ○ Modulate activity of other immune cells and secrete chemicals that amplify the activity of other immune cells → CD8 cells (cytotoxic, or killer T cells: Tc) ○ CD8 is its ID ○ After it gets activated in the lymph node, it will go to the site of infection and release granules on infected cells to kill it ○ Destroy host cells harboring anything foreign (viral infected cell; cancer cell) ○ Bind to the viral antigen and self-antigen on the surface of the infected cell ○ May kill cell directly or through enzymes that cause the cell to self-destruct