Lecture No. 6 Chapter 4 Lymphocyte and Plasma Cell PDF

Lecture No. 6 - Chapter 4 Cells and Cellular Activities of the Immune System: Lymphocytes and Plasma Cells By Gheyath K. Nasrallah, PhD  http://www.youtube.com/watch?v=iVMIZy- Y3f8...

Lecture No. 6 - Chapter 4 Cells and Cellular Activities of the Immune System: Lymphocytes and Plasma Cells By Gheyath K. Nasrallah, PhD  http://www.youtube.com/watch?v=iVMIZy- Y3f8 Vedio: http://www.youtube.com/watch?v=dTb0iEU S1oA 10/6/2024 10:01 AM Intro.to path. 3 2  Anatomic Origin and Development of Lymphocytes Lymphocyte arises from progenitor cells of the yolk sac and fetal liver  Primary (central) Lymphoid tissue in mammals  Bone marrow and/or fetal liver  Thymus  Development and maturation of lymphocytes Primary generative Secondary or or central, lymphoid peripheral organ lymphoid organ BCR(Ig ) TCR  B or T-lymphocytes passes the stages of maturation known as immunocompetent  Congenital immunodeficiency diseases are often caused by blocks at different stages of lymphocyte maturation 4 Primary and secondary lymphoid organ Distribution of lymphoid tissues in the body.  Thymus  The thymus is bilobed structure  At puberty, the thymus growth stop.  The thymus gradually loses up to 95% of its mass during the first 50 years of life  The absence or abnormal development of the thymus results in a T-lymphocyte deficiency.  Thymus  The thymus is lymphoepithelial organ.  Consist epithelial cells organized into cortical (outer) and medullary (central) that are infiltrate with thymocytes.  Sites of lymphocyte maturation ! Secondary Lymphoid Tissues  Lymph nodes  Spleen T and B-cell location  Gut-associated lymphoid tissue (GALT)  Bronchus-associated lymphoid tissue BALT  MALT???  Skin-associated lymphoid tissue  Thoracic duct  Blood  Lymph node  lymph nodes empty their products (Lymphocytes and lymphatic fluids) in the the lymphatic vessel which eventually converge in the thoracic duct.  From thoracic duct: lymphocytes and lymphatic fluid enter the circulation via vena cava, the vessel that returns blood to the heart, thus providing continual recirculation of lymphocyte.  Connective tissue Activated B cells Non-Activated B cells Plasma cells and Ab Cortical region Plasma cells and Ab FIGURE 2.10. (A) Section of a lymph node. Arrows represent the flow of lymph and lymphocytes. (B) Section through a lymph node showing T-cell zone, marginal zone, and germinal center.  Lymph node 1- Medulla:  medullary sinuses consists antibody producing plasma cells and Antibodies 2- Cortex:  Paracortical region: contains T cells  Cortical region: primary lymphoid follicles: APCs  Germinal center:  2andary lymphoid follicles: activated B-cells  Mantal zone: non-activated  Post capillary venule: Lymphocyte entry to lymph node from blood through postcapillary venule.  Efferent lymphatic vessel: lymphocyte and lymph fluid exit from lymph node  Afferent lymphatic vessels: Lymphocyte, lymphatic fluid including Ag entry in to the lymph node.  Lymphocytes and Plasma Cells Circulation of Lymphocytes (Redrawn from Anthony CP, Thibodeau GA: Textbook of anatomy and physiology, ed 12, St Louis, 1987, Mosby.)  T APC B Spleen  Largest 2ndary lymphoid organ  Highly efficient in trapping and concentrating foreign substances carried by blood  Composed  White pulp: cortical region (T lymphocytes and germinal center B lymphocyte.  Red pulp: macrophages and RBCs, and lymphocytes FIGURE 2.11. Circulation of lymph and fate of antigen following penetration through (1) bloodstream, (2) skin, and (3) gastrointestinal or respiratory tract.  Lymphoid and Nonlymphoid Surface Membrane Markers Smooth surface T cell life span months to several year Rough surface B cell T cell  Lymphocyte classification ! Surface membrane markers identified by MAb ! These markers were named as Cluster designation or cluster of differentiation (CD) antigens. ! CD has different function includes: ! promote cell-to-cell interactions and adhesion. ! Transduction of signals that lead to lymphocyte activation ! Cells classification  Major distinguishing markers Marker B cell Tc-cytotoxic Th-helper Antigen R BCR (surface Ig) TCR TCR CD3 -- + + CD4 -- -- + CD8 -- + -- CD19/ CD20 + -- -- CD40 + -- -- CD2??  Classes of lymphocytes Abbas, Lichtman and Pillai. Cellular and Molecular Immunology, 7th edition, 2011 c Elsevier  T cell maturation  T cells originate from bone marrow and maturate in the thymus  In the thymus, T lymphocytes (thymocytes) undergo random recombination of their T-cell receptor genes.  Some of the resulting T-cell receptors will be specific for pathogens and others for normal self- antigens. The role of the thymus is to select T cells that will respond to pathogens but not self-antigens  T cells recognize self Ag are forced to undergo apoptosis. 21  T- cell maturation in the thymus 1  After leaving bone marrow, immature T-cells (thymocytes, 2 or T-cell precursor reach thymus).  Increase thymocytes population of by cell division.  Undergo positive and negative selection  Only 2-3% of T-cell 3 precursor survived after the 4 positive and negative selections mature into CD4+ ?? or CD8+ T-cells Naïve T cells ready for activation T- cell activation in the secondary lymphoid organ (lymph nodes). Mature Naïve T-cells in the thymus Peripheral blood (circulation) Lymph nodes Encountering of foreign Ag presented on MHC of APC will leads to activation: proliferation and differentiation of Eeffector and Memory cells the type of cell and presentation is based on the Activated effector Th (or Tc) and memory cell  T-Lymphocyte Subsets 1- Helper T (Th, CD4+) lymphocytes: classified according to the cytokine they produced: in the thymus they are naive but after exposure to the antigen they meet. Based on the type of antigen Th1: cell-mediated effector mechanisms. Th2: regulation of antibody production. Treg (regulatory T cells): an immunoregulatory type Th17: activation of infected epithelial mucosal immunity and transplantation cells and important in autoimmune disease 2- Cytotoxic T (CTL, Tc, CD8+) : capable of directly destroying virally infected and malignant target cells 3- Suppressor T (Ts, CD8+) : downregulate actions of other T and B cells.  T-Lymphocyte Subsets The following factors can influence the terminal differentiation of T Th2-IgE-parasitic infection lymphocytes: The nature of the antigen is the most important factor  Type of antigen and antigen- presenting cell (APC).  Affinity of the specific antigenic peptide. chronic is Th1/ in vaccines they prefer Th1 over Th2 to kill the infected cell because of the allergic reaction associated with the Th2  Types of co-stimulatory if the site of infection has a lot of mast cells (costimulatory) molecules expressed by APCs.  Cytokines acting on T cell during primary activation through TCR. The presence of interleukin-12 (IL-12) during primary T-cell activation leads to strong development of Th1 responses, and IL-4 promotes Th2 development.  Th1 VS Th2 response IL-12 or other signals Ab-mediated killing Cell mediated killing anaphlactic shock  T-Regulatory Lymphocytes (CD4+)  Treg cells are immunoregulatory: cells that control autoimmunity in the peripheral blood through “dominant tolerance.” Types of Treg cells include the following: Natural CD4+ Treg cells Th3 cells Tr1 cells CD8+ Treg cells  General functions of CD8+ Tc they produce apoptotic factors and leave inducing apoptosis in the cells  Most Tc that are CD8+ recognize antigen in conjunction with class I MHC molecules.  Eliminate viral infected cells and non-self (graft) and Tumor cells Before interaction with Tc transformed (tumor cells)  They lyse target cells via similar mechanism mechanisms as NK cells. Hela tumor cells recognized by the ag 28 Tumor cells after interaction with Tc General functions of CD8+ cytotoxic T cell (Tc) Mechanisms of target cell killing by NK or Tc  Vesicles contains perforins, granzymes, and TNF 10/6/2024 10:01 Intro. to path. 30 AM  Mechanisms of target cell killing by NK or Tc I- Secreted proteins (enzymes)  NK and Tc attached to infected cell and releases cytoplasmic vesicles  Vesicles contains  A- Perforins facilitate entry of granszymes into infected cells  Granzyme activate cytoplasmic protein called BID  BID activate cytochrome release from the mitochondria  The cytocrome release trigger the caspase pathways which leads into apoptosis  Granzyme can also directly activate capspases-3 which trigger caspase activated deoxyribonucease (CAD) which leads to apoptosis of the infected cells  CAD induces apoptosis by degrading the infected cell DNA  CAD can also degrade viral DNA  B- TNF: bind to TNF receptor (TNFR) and activate apoptosis  C- granulysin: antimicrobial compound (only in NK vesicles) II- Ligands: surface molecule Tc called Fas bind to Fas ligand FasL: activate apoptosis big role in viral killing Mechanisms of target cell killing by NK or Tc BAX cascade from 1-9 CAD (Caspase Activated Deoxyribonucease) 32 General functions of CD4+ T-helper cells  No cytotoxic or phagocytic activity. i.e. they can not destroy extracellular bacteria or infected cells. They help other immune cells: they activate and direct other immune cells. -Activation of cell mediated immunity: activation Tc, NK, macrophage activity and B-cells (Th1-response). - Promote the Ab-mediated immunity: Help B-cells to produce Ab and class switching of Ab (IgE) by B-cells (Th- 2 response). Antigen Recognition by T Cells  T cells undergo antigen presentation only by self-MHC molecules. P ZAP-70 Signal transduction  T-cell activation by APC T-cell activation also requires at least 3 signals 1- Binding of CD4 (or CD8) with the MHC class II (or MHC-I) 2- Phosphorylation of CD3 zeta chain and particular kinases. 3- Costimulatory signal (e.g., interaction between marker CD28 on T cell and marker CD80 on APC.  Activation of T cells can lead to the following: Cell division Cytokine secretion by T cell Expression by T cell of antigens associated with activated state 35  T-cell activation by APC  Anergic If a cell does not receive a full set of signals, it will not divide, and it may even become in resting state (G0 or G1):  When activated by the proper signals, T cells may carry out one or more of the following functions: 1. Proliferation 2. Differentiation 3. Production of cytokines 4. Development of effector function and memory 10/6/2024 10:01 AM 36  T-cell activation by APC ! Antigen Processing and Antigen Presentation to T Cells  Endogenous pathway  Exogenous pathway Signals need for B cell activation and class switching  T-independent antigen Triggering T-Independent Antigen Triggering ! Some antigens (e.g., dextran) can trigger B cells without help from T cells; these are T-independent antigens (athymic activation). ! Generally, these antigens are not strong, provoke mainly IgM responses, and induce little immunologic memory. super ag does not need to be presented ut cross links the two receptors ! Super Ag: cross liking of MHC with TCR or two BCR ! Mitogens: chemical enhance mitosis (MAPK?), usually a protein but could be LPS. Examples?  SuperAg activates any clone many cytokines are produced it produces cytokine shock and gives us septic shock septic shock can be caused by certain bacterial proteins like staph aureus septic shock syndrome https://www.google.com.qa/search?q=superantigen&biw=1455&bih=705&tbm=isch&imgil=XYSZgPegBcE3ZM%253A%253B4I2hY2Fwd7JWLM%253Bh ttps%25253A%25252F%25252Fescholarship.org%25252Fuc%25252Fitem%25252F47g8w51m&source=iu&pf=m&fir=XYSZgPegBcE3ZM%253A%252 C4I2hY2Fwd7JWLM%252C_&usg=__StXwSKrxmGA-- m0phpt6OivGg8c%3D&ved=0CDMQyjc&ei=rRNWVPfROo7esASOloLoBQ#facrc=_&imgdii=_&imgrc=JRa2vRtJP_S2FM%253A%3BLgH9qJ6J7rOikM% 3Bhttp%253A%252F%252Fwww.nature.com%252Fnm%252Fjournal%252Fv6%252Fn4%252Fimages%252Fnm0400_378_F1.gif%3Bhttp%253A%252 F%252Fwww.nature.com%252Fnm%252Fjournal%252Fv6%252Fn4%252Ffig_tab%252Fnm0400_378_F1.html%3B560%3B865  Mitogen these proteins are used to induce proliferation ogf b cell or t cell and it activates —-— used in the flowcytomytery instead of lps as the conc of lps (high) gives us wrong result  B Lymphocytes ! Cell Surface Markers 1. Ig receptor: an antibody molecule with antigenic specificity. 2. Fc receptor: specifically binds the Fc portion of IgG; may aid B cells in binding to Ag already bound to Ab. 3. Complement receptors: C3R, function not understood. 4. B-cell surface Ags: coded by MHC-II genes. 5. Two types: nonspecific IgM and IgG  B1 cells possess CD5 marker, low affinity IgM & IgG to antigen, found in peritoneal & pleural cavity and  B2 cells account for the majority of B lymphocytes in adults (includes B-reg)  B Lymphocytes activation and maturation  B-cell maturation: Bone marrow and GALT  B-Cell Activation: B cells can be stimulated in their resting state to: Enlarge. Develop synthetic machinery. Divide. Mature. Secrete antibody.  B-cells can be activated Independently from T cells Example: LPS (mitogen) Other example of mitogens???  Phases of B-lymphocyte activation B-cell TH activation proliferation differentiation 44  Types of B- cell activation 2- T-cell independent activation (week response) Type-A: B cell binds to an Ag and receives secondary activation signal through TLR. Type B is when the antigen is a molecule with multiple repeating subunits (LPS peptidoglycan) which can simultaneously cross link enough B cell receptors to fully activate the B cell. Type-B: cross linking can act as an apc 45  Plasma Cell Biology ! Rarely seen in circulation, 2% of BM cells. ! Function is synthesis and excretion of Igs. ! Plasma cells arise as end stage of B-cell differentiation. ! Pathway from B cell to plasma cell occurs when B cell is antigenically stimulated (signal 1) and undergoes transformation as a result of stimulation of various interleukins (signal 2). ! An increase in plasma cells can be seen in:  A variety of non-malignant disorders: such as viral autoimmune diseases also fall within this category disease, chronic infections, allergic conditions, and collagen diseases.  Malignant disorders: multiple myeloma (plasma cells in bone marrow).  Other Types of Lymphocytes ! NK cells (granulated lymphocytes): discussed earlier. ! Memory T and B cells : long-lived T or B cells that have been stimulated by antigen  Other Types of Lymphocytes ! NK cells (granulated lymphocytes): discussed earlier. ! Virgin or naive lymphocytes: have not encountered their specific antigen. ! Memory cells: long-lived T or B cells that have been stimulated by antigen  Memory B-cells carry surface IgG  Memory T cells carry: CD45RO variant of leukocyte common Ag and increase CAM and VCAM (LFA-3 and very late adhesion Ag VLA-4)  NK and K-Type Lymphocytes ! 1-6 % of circulating lymphocytes ! classified as effector: activated by IFNɤ, IL-12, IL-15, IL-18, IL-2,& secretes IFNɤ and IFNα. ! Used to be known as null cells ! Membrane markers: CD2, CD16, CD56, CD57 and occasionally CD8. ! NK cells: 70-80% are Large granular lymphocyetes (LGLs), destroy target cells through an extracellular, nonphagocytic mechanism called cytotoxic reaction, MHC-unrestricted cytolysis. ! Antigen recognition by NK cells:  KIR  ADCC  NK cells uses CD2, or CD69, NKR-P1 and FCϫR (CD56)  NK cells recognize CAMs (such as β2-integrens) on target cells. Natural Killer and K-Type Lymphocytes NK cells respond to cross-linking of CD16 and CD69 as follows: Increasing the rate of proliferation of NK cells. Elevating the levels of tumor necrosis factor production within 4 hours of stimulation. Increasing the expression of CD69 on the cell surface of NK cells. Increasing the cytotoxicity activity against a normally resistant cell line (P815). K cells : by ADCC Disorders with Immunologic Origins ! Primary immunodeficiency metabloic mutations where nucleotides or specific enzymes are not produced  Monogenic (Mendelian) mono or polygenic  200 clinical phenotype not all mutations are shown during eary stages only  75% in children less than 5 years. ! Secondary immunodeficiency  Disease or therapy cause the immune defect such as HIV, leukemia or immunosupressive drug. ! Immuno-Mediated disease autoimmunity transplantation cancer  Primary Immune Disorders severe combined immunodefecincy RAG-1 and RAG-2 Immune Deficiencies (self studies and student presentations) Immune Deficiencies (self studies and student presentations) Disorders with Immunologic Origins Btk deficiency  Alterations in Lymphocyte Subsets ! The ratio of Th to Tc lymphocytes (Th:Tc ratio) is about 2:1 ! This ration can be reversed under certain condition such as HIV and leukemia. ! Older adults: increase in Th cells and decrease in Tc cells. ! B cells: total number remains unchanged, however serum IgM decreased and IgA and IgG increase. Basic Evaluation of immune syndrome ! A complete blood count (CBC) and erythrocyte sedimentation rate (ESR) are cost-effective screening tests. ! Calculate the absolute lymphocyte count. lymphocyte 25-50  most of these disease conditions are monogenic Evaluation of Suspected Defects Screen for titer of blood group Vaccine with Protein Ag and maybe CHO Ag at 0 and 2weeks later we can assess the titer of anti A and anti B If someone has specific antibody defeciency we inject them with a vaccines TBD vaccine Rosette and Delayed type hypersensitivity. Measure the area 48-72 hours FACS assay after injection micobacterium tubercleosis has delayed type hypersensitvity chronic NBT reacts with granumlatous disease ROS produce by CGD and LAD Leukocyte adhesion phagocyte (Burst deficiency test) https://www.memorangapp.com/flashcards/95295/Immunology+L2+Cells+of+the+Im mune+System/ we expect that we have functional t cells  Evaluation of Suspected Defects  Cell-Mediated Immune System ! Increase recurrent viral, parasitic, fungal infection ! Diagnosis  Candida skin test  Erythrocyte rosette formation (gold standard)?????  MAb: Flowcytometry.  Humoral system activate lympocyte proliferation by antigens like lps and fitohemagglutinin they will start with replication CD2 will bind to the sheep rbcs and each will  Measuring Ig subset concentration  Lymphocyte system  B and T cell Rosette assay and FACS Activate lymphocyte with PHA or LPS (high expression of CD2) for 2 days then add sheep RBC: 60- 80% of activated T cell should form E-Rosette. ! T-Cell Activation Defects  Defective surface expression of CD3–T- cell antigen receptor complex.  Defective signal transduction from T-cell antigen receptor to intracellular metabolic pathways. NFkappa B: cytokine  Pretranslational defect in interleukin-2 (IL- 2) and/or other cytokine production. recurrent infection Other Primary Immunodeficiencies  Immune-Mediated Disease recurrent ab production/ chronic inflammation