Cellular Immune Response II PDF 2024

Cellular Immune Response II Dr. Abdulrahman Alsultan 6 / 11 / 2024 Lecture outline 1. Types of CMI killing microorganisms (Role of CD4+ & CD8+ T lymphocytes). 2. Various types of CD4+ Helper T cells. (Mechanisms determining differentiation) 3. Role of CD4+ Th1 lymphocytes in defe...

Cellular Immune Response II Dr. Abdulrahman Alsultan 6 / 11 / 2024 Lecture outline 1. Types of CMI killing microorganisms (Role of CD4+ & CD8+ T lymphocytes). 2. Various types of CD4+ Helper T cells. (Mechanisms determining differentiation) 3. Role of CD4+ Th1 lymphocytes in defense against intracellular pathogens. 4. (What is Delayed hypersensitivity) 5. Role of CD4+ Th2 lymphocytes in defense against helminths. 6. Ways CD8+ effector T lymphocytes can kill a virus infected cell. 7. Features of regulatory T lymphocytes & their role in suppression of CMI. 2  What is the responding T cell ? Defense against intracellular microbes is called cell mediated immunity CMI , because its mediated by cells which are called T lymphocytes. ?? ?? Some T lymphocytes activate phagocytes to destroy microbes that have been ingested by the phagocytes into intracellular vesicles. Other T lymphocytes kill any type of host cell that harboring infectious microbes in the cytoplasm. ?? ?? 3  What is the types of cell mediated immunity ? Two types of cell-mediated immune reactions are deigned to eliminate different types of microbes. 1 2 CD4+ helper T cells secrete cytokines that recruit and activate other leukocytes to phagocytes ingest and destroy microbes. CD8+ cytotoxic T lymphocytes kill any infected cell containing microbial proteins in the cytosol or nucleus eliminating cellular reservoirs of infection. 4 Characteristics of subsets of CD4 helper T cells 5 6 General properties of T cell Cytokines 7 Biologic actions of selected T cell cytokines Reg.T cells 8  Functions of Th1 CD4+ Effector T lymphocyte Th1 cell : Stimulate the production of Ab that promote the ingestion of microbes by the phagocytes. Killing of microbe by producing IFN as a key component of cell mediated immunity. 9  Role of Th1 cells in defense against intracellular pathogens Th1 cell Recognize Ag 10  What is delayed hypersensitivity? Delayed hypersensitivity, also known as Type IV hypersensitivity, Its an immune reaction that typically takes 24–72 hours to develop after exposure to an antigen. Delayed hypersensitivity is mediated by T cells rather than antibodies. 11  Mechanism determining which direction activated CD4+ T cell differentiate 1. Pathogen type 2. Cytokine (APC) 3. Activation of transcription factors. 4. Cytokine (effector cell ) 12 Role of Th2 cells in defense against helminths Th2 cells: stimulate phagocyte independent, eosinophil-mediated immunity, which is especially effective against helminthic parasites. In chronic parasitic infections or allergic disease 13 Classical & Alternative macrophage activation 14  Balance between Th1 &Th2 cell activation determines outcome of intracellular infection Naive CD4+ T lymphocytes may differentiate into : Th1 cells : that activate phagocytes to kill ingested microbes. Th2 cell : that inhibit classical macrophage activation. 15 Uncontrolled mycobacterium leprae leads to lepromatous leprosy Inhibition of mycobacterium leprae leads to tuberculoid form 16  CTLs: recognize class I How can CD8+ Effector T cells kill cells MHC of cytoplasmic infected with virus? microbes in infected 2 1 cells and form adhesion Apoptosis with these cells Apoptosis Caspases Caspases Adhesion molecules to stabilize the binding of CTLs to infected cells Fas (CD95) The CTLs : are activated Granzyme B to release exocytose granule and granzymes Fas ligand towered the infected cell Granzymes are deleverd to the cytosol of the target cell. Granzymes then induce apoptosis. I. synapse 17  Cooperation between CD4+ and CD8+ T cells Together we can !!! Th TCL CD4+ T cells: recognize Ags derived from the vesicular microbes and activate the macrophages to kill the microbes in the vesicles. CD8+ T cells: recognize Ags derived from the cytoplasmic bacteria and are needed to kill the infected cell. 1 2 That eliminating the reservoir of infection. 18 What are Regulatory T lymphocytes ? Subset of CD4+Tcells Has surface molecule: CTLA4 binds B7(APC) Function is to: Shut off T cell response 19 20