Intro to Immunology 3&4 (B,T cells)

<p>Regulating the immune system</p> Signup and view all the answers

<p>Using membrane-bound antibodies as receptors</p> Signup and view all the answers

<p>50,000 copies</p> Signup and view all the answers

<p>Two light chains and two heavy chains</p> Signup and view all the answers

<p>Antigens</p> Signup and view all the answers

<p>Hyper variable region</p> Signup and view all the answers

<p>Express peptide antigens</p> Signup and view all the answers

<p>Thousands</p> Signup and view all the answers

<p>Bind to MHC molecules</p> Signup and view all the answers

<p>HLA molecules</p> Signup and view all the answers

<p>Peptide antigens</p> Signup and view all the answers

<p>Bind to peptide antigens</p> Signup and view all the answers

<p>Form the antigen binding site</p> Signup and view all the answers

<p>Hyper variable region</p> Signup and view all the answers

<p>MHC molecules present peptide antigens to T cells.</p> Signup and view all the answers

<p>TCRs bind to peptide antigens presented by MHC molecules.</p> Signup and view all the answers

<p>T cells can recognize peptide antigens.</p> Signup and view all the answers

<p>B cells produce antibodies and mediate humoral immune responses.</p> Signup and view all the answers

<p>The hyper variable region formed by the tips of the alpha and beta TCR chains is unique to each T cell.</p> Signup and view all the answers

<p>Antibodies bind to antigens.</p> Signup and view all the answers

<p>CD4+ T cells help coordinate immune responses and activate other immune cells.</p> Signup and view all the answers

<p>MHC molecules are also referred to as HLA (Human Leukocyte Antigens).</p> Signup and view all the answers

<p>B lymphocytes have an important function in the adaptive immune system. They are responsible for humoral immune responses which are mediated by antibody molecules secreted by plasma cells.</p> Signup and view all the answers

<p>T lymphocytes are responsible for cellular immune responses and thus have a key role in defence against intracellular pathogens.</p> Signup and view all the answers

<p>The two types of T lymphocytes are CD4+ T cells (Helper T cells) and CD8+ T cells (Cytotoxic T cells). CD4+ T cells are the key regulators of the entire immune system, sending signals for cytokines to perform their functions. CD8+ T cells kill virally infected body cells.</p> Signup and view all the answers

<p>B and T cells mature to distinguish self from non-self through a process called acquired immune tolerance. If they react to self antigens, they are usually destroyed or inactivated.</p> Signup and view all the answers

<p>Acquired immune cells use specific recognition to detect invading pathogens. The pathogens have unique structures called antigens that are recognized by the adaptive leukocytes.</p> Signup and view all the answers

<p>Antibodies are proteins that bind to one specific antigen. They are a complex of four polypeptide chains, which include 2 light chains and 2 heavy chains.</p> Signup and view all the answers

<p>B cells use membrane-bound antibodies as receptors to recognize and bind to membrane-associated or soluble antigens.</p> Signup and view all the answers

<p>IgG and IgA</p> Signup and view all the answers

<p>Bone marrow</p> Signup and view all the answers

<p>B and T cells normally circulate around their primary lymphoid tissue (site of development - bone marrow/thymus) in their inactive form</p> Signup and view all the answers

<p>Antigen presentation activates the B cells and T cells in secondary lymphoid tissue (e.g. lymph nodes, spleen, MALT)</p> Signup and view all the answers

<p>B cell activation and the eventual production of high affinity antibodies.</p> Signup and view all the answers

<ol> <li>Membrane-bound antibodies on the B cells bind to target antigen IgM (or IgD) within the B cell zone of lymph nodes</li> <li>B cells require 2 signals to become fully active and begin proliferation - the antigen and ‘helper signals’ e.g. from TH cells, PRR and PAMPs or from multiple antigens</li> <li>Once activated, they clonally proliferate and become either a plasma cell (antibodies) or a memory B cell - germinal centre response</li> <li>High affinity antibodies are generated - IgM (produced by plasma cells) → IgG (produced by B cells responding to certain antigens), assisted by TH cells</li> </ol> Signup and view all the answers

<p>Signal 1- BCR and antigen complex Signal 2- T cell independent reaction therefore it requires PRR+PAMP complex. This produces low affinity antibodies and short lived plasma cells. Without the help of T cell response, it only provides a short lived response and no Memory cells.</p> Signup and view all the answers

<p>Signal 1- BCR binding to antigen Signal 2- For T-dependent antigens, which are typically proteins, an additional co-stimulatory signal is required for full B cell activation. After BCR engagement with the antigen, the B cell presents processed antigenic peptides on its surface using (MHC II) molecules. Interaction between the B cell and a CD4+ helper T cell occurs when the T cell recognizes the antigen-MHC II complex on the B cell surface. This interaction provides the second signal.</p> Signup and view all the answers

<p>1)Recognition function- Binding to antigen mediated by variable region sites. 2)Effector function- Clearance mechanisms mediated interaction of the heavy chain constant region with effector molecules.</p> Signup and view all the answers

<p>B cell activation, agglutination (immune complex formation - enhances phagocytosis), complement system activation through classical pathway</p> Signup and view all the answers

<p>IgG</p> Signup and view all the answers

<p>IgA</p> Signup and view all the answers

<p>Produced in allergic response</p> Signup and view all the answers

<ul> <li>helps with neutralization of pathogens (membrane bound form)</li> <li>Dimer in secretory fluids (e.g. colostrum) <ul> <li>Neonatal defense - protects GI tract of neonates</li> </ul> </li> </ul> Signup and view all the answers

<p>IgG&gt;IgA&gt;IgM&gt;IgD&gt;IgE</p> Signup and view all the answers

<p>It plays a role in B cell activation.</p> Signup and view all the answers

<p>foetal immunity (placental transfer), complement activation, NK cell activation, neutralisation, opsonisation, agglutination</p> Signup and view all the answers

<p>Innate immune response- Intracellular pathogens infect host cells. The PAMPs stimulate the secretion of Interferons alpha and beta (IFN alpha/beta). These interferons activate the natural killer cells which perform the killing of infected host cells and produce pro inflammatory mediators.</p> Signup and view all the answers

<p>The antigen bound IgG is a good activator of natural killer cells which then performs the killing of infected host cells by apoptosis and produces pro inflammatory mediators.</p> Signup and view all the answers

<p>CD4+ Helper T cells activate B cells and stimulate production of memory B cells.</p> Signup and view all the answers

<p>CD8+ Killer T cells kill infected cells via perforin, granzymes, and granulysin.</p> Signup and view all the answers

<p>Regulatory T cells suppress lymphocyte activity.</p> Signup and view all the answers

<p>Class I MHC: expressed on all nucleated cells, present peptide antigens to CD8+ killer T cells; Class II MHC: expressed only on antigen presenting cells (e.g. dendrites, macrophages), present peptide antigens to CD4+ helper T cells</p> Signup and view all the answers

<p>MHC molecules present peptide antigens to T cells, allowing T cells to recognize and respond to specific antigens</p> Signup and view all the answers

<p>CD8+ killer T cells: recognize peptide antigens presented by Class I MHC molecules and destroy infected cells; CD4+ helper T cells: recognize peptide antigens presented by Class II MHC molecules and help coordinate immune responses</p> Signup and view all the answers

<p>Class I MHC: presented to CD8+ killer T cells, Class II MHC: presented to CD4+ helper T cells</p> Signup and view all the answers

<p>Expressed on all nucleated cells, present peptide antigens to CD8+ killer T cells</p> Signup and view all the answers

<p>Expressed only on antigen presenting cells (e.g. dendritic cells, macrophages), present peptide antigens to CD4+ helper T cells</p> Signup and view all the answers

<ol> <li>Dendritic cells recognise and phagocytose antigenic debris</li> <li>In the presence of pro-inflammatory mediators (e.g. TNF⍺), the dendritic cells mature and increase expression of stimulatory molecules on their surface</li> <li>Dendritic cells phagocytose the pathogenic antigens, break the antigens down into short peptides and load them onto MHC II molecules</li> <li>MHC II molecules transported to cell surface <ol> <li>At the same time, the maturing dendritic cells migrate into the lymph nodes via the afferent lymphatic vessels</li> </ol> </li> <li>Co-stimulatory molecules enable T cell to respond to antigen and fully differentiate</li> </ol> Signup and view all the answers

<p>The dendritic cell expresses the MHC II peptide, it forms a complex with the antigen activated CD4+ T cell. The CD4+ T cell secretes T cell growth factors called IL-2 which are autocrine mediated. These IL-2 growth factors promote T cell proliferation and differentiation.</p> Signup and view all the answers

<p>TH1 cells: secrete pro-inflammatory cytokines (IL2, IFN𝛾), which stimulates production of Reactive Oxygen Species (macrophage-mediated)-(switch on expression of NADPH oxidase genes). This allows the macrophages to kill the bacteria much more effectively.</p> Signup and view all the answers

<p>TH2 cells: secrete mainly IL4, IL5 and IL6 which promote B cell proliferation and induces antibody production. Th2 cells stimulate and recruit specialized subsets of immune cells, such as eosinophils and basophils, to the site of infection or in response to allergens or toxins.</p> Signup and view all the answers

<p>FH cells: stimulated by presented antigen peptides + MHC II molecules on B cell, then stimulate the B cells to proliferate and differentiate (plasma + memory) by secreting IL4 and IL21</p> Signup and view all the answers

<p>IL-2 (provided by TH cells) promotes differentiation and proliferation of antigen activated (via MHC I) CD8+ cells into cytotoxic T lymphocytes (CTLs)</p> Signup and view all the answers

<ul> <li>CTLs migrate out of secondary nodes and enter site of infection (via transendothelial migration) and then kill virally infected host cells by recognizing pathogenic antigens attached to MHC class I <ul> <li>Also involved in killing cancer cells</li> </ul> </li> </ul> Signup and view all the answers

<p>There are proteins in lytic granules of cytotoxic T cells:-Perforin, Granzymes and Granulysin. These substances are secreted in order to kill in a similar mechanism to NK cells.</p> Signup and view all the answers

<p>It is a cytotoxic granule secreted by the T cell polymerises to form a pore in the target membrane.</p> Signup and view all the answers

<p>Granzymes are secreted by cytotoxic T cells. They are serine proteases, which activate apoptosis once in the cytoplasm of the target cell.</p> Signup and view all the answers

<p>Granulysin is a substance secreted by the Cytotoxic T cells which induces apoptosis in infected host cells.</p> Signup and view all the answers