Biochemistry & Immunology in Nursing (NRS414) Past Paper PDF

27/12/2024 2 BIOCHEMISTRY & IMMUNOLOGY LEARNING OBJECTIVES IN NURSING (NRS414)...

27/12/2024 2 BIOCHEMISTRY & IMMUNOLOGY LEARNING OBJECTIVES IN NURSING (NRS414) AT THE END OF THE LESSON, STUDENTS ARE ABLE TO EXPLAIN OR IDENTIFY: I. B lymphocytes and antibody response. II. Activation of B cells. III. Primary and secondary responses. IV. T cells and mechanism of their activations. NRS421 HS240 HS260 3 4 B-Cell Activation B Lymphocyte and Antibody Response ✓ Ag binds to a B-cell receptor, the B-cell internalizes the Ag, enclosing within a membrane-bound vacuole inside the B cell. Antigen binds to B cell receptor ✓ Ag is degraded into peptide fragments – delivered to proteins MHC Poises (self-control) B cell to respond class II molecules that the move to the B-cell surface – process called antigen presentation (pieces of the Ag is presented for inspection of In many cases B cell needs conformation from helper TH cells. T (TH) cells. B cells activated dividing and ✓ T cells have on their surface multiple copies of an antigen-specific differentiating to produce antibodies. receptor called T-cell receptor (analogous to B-cell receptor). Antigen (Ag) enters the body and is phagocytized and ✓ TH receptor binds to one the peptide fragments being presented by processed by macrophages the B-cell – activation of B cell. ✓ If the TH fails to recognize any of the fragments being presented by These macrophages destroy Ag and present a portion the B-cell – unresponsive to future exposure to the antigen – on the surface of the macrophage tolerance to that particular Ag. Macrophages are called antigen-presenting cells (APC) ✓ However, the above mechanism is important in avoiding erroneous responses against ‘self’ and other Ag. #MHC: Major histocompatibility complex 5 6 B-Cell Activation B-Cell Activation https://youtu.be/iIJulGXWm6Q https://youtu.be/_qF2jEe7ZWc 1  27/12/2024 7 8 Characteristic of Activated B Cells Function – to enhance the 2. Class switching – initial immune response: program – secrete IgM. 1. Affinity maturation - Switch genetic program – B cells bind Ag for the secrete other class of Ab – longest duration will to meet the most effective proliferate. mechanism against specific Figure shows +++ – Ag. Circulating B cells indicate the most “fit” most commonly switch to binding which will IgG production. B cells in continue proliferation. The mucosal associated ++ will undergo apoptosis. lymphoid tissues – switch to IgA. 9 10 3. Formation of memory cells – some of the B cells from class switching – form memory cells – persist in the body for years – sufficient to give a prompt and effective 2o response when the same Ag is encountered again later time. As Ab clear the Ag, the Ab response is reduced. The remaining Ag stimulate the lymphocytes to undergo apoptosis. Memory B cells – long lived – even in the absence of Ag 11 12 Characteristic of Primary Response Lag period of 10 days – 2 weeks occurs before antibody detection in blood (low amount of Ab). During this delay, the individual could very well experience symptoms of an infection. However, the immune system is actively responding Characteristics of where naïve B cells present Ag to TH cells resulting in B- cell activation. Activated B cells proliferate and differentiate into Secondary Response increasing numbers of plasma cells as long as antigen is present – secrete thousand of Ab. Net result is slow steady increase in antibody titer (concentration of Ab) 2  27/12/2024 13 14 1. First response to an antigen – 5. Cytokines trigger recognized by host B cells. proliferating B cells to 2. B cells divide to form plasma cells – begin to synthesize antibodies switch from making plasma cells that produce IgG. Secondary Response 7. B cells formed memory cells persist in lymphoid tissues. They do not participate in initial response, but they retain their ability to recognize a particular antigen. 8. When an antigen recognized by memory cells 6. As IgM production decreases, IgG enters the blood, secondary response occurs. Lag period production accelerates then decreases. 9. Secondary response react much faster. IgM (smaller quantities and short period) is produced before IgG (followed sooner after IgM and in large quantities) 3. In few days, antibodies begin to appear in the blood plasma, increase concentration over a period of time of 1 to 10 weeks. 4. First antibodies – IgM – bind directly to foreign substances. 15 16 17 18 Primary & Secondary Immune Response https://youtu.be/qUG4-yZVPUQ 3  27/12/2024 19 20 GENERAL CHARACTERISTIC OF T CELLS T Lymphocytes Antigen Recognition and Response Have multiple copies of cell receptors on their surface T-cell receptor (TCR) consists of two polypeptide chains (either a ❑ During antigen presentation, the peptides from the set of alpha and beta or gamma and delta) antigen are cradled in the groove of major Receptors have variable region to recognize a specific antigen histocompatibility complex molecule (MHC molecule) Role of T cells different from B cells T cells never produce antibodies Two types MHC T cells armed with effectors that interact directly with other cells MHC class I binds: T cell receptor does not react with free antigen endogenous antigens – made within the cells Antigen must be present by APC MHC class II binds: exogenous antigen – taken up by a cell ❑ MHC I – produced by all nucleated cells ❑ MHC II – produced by APC i.e dendritic cells, B cells and macrophages Disulfide bond 21 22 Endogenous Exogenous antigens antigens MHC https://youtu.be/t81EjpkCiss 23 24 T Lymphocytes Antigen Recognition and Response Two major function of T cell populations Cytotoxic T cells Proliferate and differentiate to destroy infected or cancerous “self” cells Have CD8 marker Recognize MHC class I (endogenous antigens) Helper T cells Multiply and develop into cells that activate B cells and macrophages Stimulate other T cells; orchestrate immune response Have CD4 marker Recognize antigen display by MHC class II (exogenous antigens) 4  27/12/2024 25 26 Activation of T Cells Dendritic cells – play crucial role in T-cell activation. Immature dendritic cells – in peripheral tissues (beneath the skin) – gather various materials from skin by phagocytosis and pinocytosis Dendritic cells – located below mucous membrane – use tentacle-like projections – send between the epithelial cells – able to sample materials from the lumen and intestine. Dendritic cells travel to secondary lymphoid organ – mature to a form able to present Ag to naïve T cells. Upon activation, T cells produce cytokine that stimulates T-cell growth (IL-2). T cells also produce adhesion molecules when activated. Acquire their effector functions. 27 28 T Lymphocytes Antigen Recognition and Response T-Cell Activation Functions of Tc (CD8) cells Induce apoptosis in “self” cells https://youtu.be/JPh9P1aEfMI Cells infected with virus or intracellular microbe Destroys cancerous “self” cells Nucleated cells degrade portion of proteins Load peptides into groove of MHC class I molecule MHC class I molecule recognized by circulating Tc cell Cell destroyed by lethal effector function of Tc cell Tc cells releases pre-formed cytokines to destroy cell 29 30 5  27/12/2024 31 32 Functions of T H (CD4) cells Orchestrate immune response Recognize antigen presented by MHC class II molecules Cytotoxic T Cell MHC class II molecules found only on APC If TH cell recognizes antigen, cytokines are delivered Cytokines activate APC to destroy antigen https://youtu.be/5TcH3ITMqOM Notes: Cytokines are produced by a broad range of cells, including macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells; a cytokine may be produced by more than one type of cell 33 34 T Lymphocytes Antigen Recognition and Response 35 36 T Lymphocytes Antigen Recognition and Response Role of TH cells in B cell activation If TH cell encounters B cell bearing peptide: Helper T Cell MHC class II complex https://youtu.be/RUmmqFZQx9A TH cell responds by producing cytokines B cell is activated in response to cytokine stimulation B cell proliferates and undergoes class switching Also drives formation of B memory cells 6  27/12/2024 37 38 T Lymphocytes Antigen Recognition and Response Role of TH cells in macrophage activation Macrophages routinely engulf invading microbes resistant to lysosomal killing TH cells recognize macrophage with engulfed microbes resistant to killing TH cells activate macrophages by delivering cytokines that induce more potent destructive mechanisms 39 Lymphocyte Development During lymphocyte development, B and T cells acquire ability to recognize distinct epitopes (from pathogens) Once committed to specific antigen, cells “checked out” to ensure proper function B cells undergo developmental stages in bone marrow T cells go through process in thymus 7