METHODICAL INSTRUCTION
Practical class №1
- THEME.Structure and principles of functioning of immune system.Immune inflammation.Age immunology (5 academic hours).
- Background:to familiarize students with the subject of сlinical immunology and allergology; the current understanding of the antigen recognition (structure of antigen receptors of T and B cells, MHC molecules and MHC processing); regulation of the immune response (development of the immune system, the anatomy of the organs involved in the immune system,mechanisms of B and T cells regulation) and the processes in the formation of immune response.
3 Aim:
- Study: Students need to learn the basic modern data on the structure and function of all parts of the immune system;
- Professionally oriented: Students should know the basic stages of the immune response and the types of regulation;
- Educational: to form students' sense of responsibility for the timeliness and appropriateness of professional activities.
4. Materials: Equipment to run powerpoint presentation.
Main books. Short information on the topic.
5. Interdiscipline integration
5.1. Interdiscipline integration: The theme of this practical lesson is related to the themes set out in the course of general immunology: the organs and cells of the immune system, the structure and function of immunoglobulins, types of immune response, antigens, innate and acquired immunity.
Subject / Know / CanAnatomy / Haemopoietic organs of immune system / Name primary and secondary lymphoid organs, lymphatic ducts
Biology, histology, embryology. / Immunity as mechanism of functional and structure homeostasis. Essentials of immuno-embryogenesis. / Distinguish basic phylogenetic levels of immunity evolution, primitive cell-mediated immunity and integral cell-mediated and humoral immunity
Biochemistry / Chemical structure and biological action of mediators of cell-mediated immunity / Immunophoretic determination of immunoglobulins.
Pathophysiology / Phagocytosis in the focus of inflammation, immunological tolerance, reactivity, allergy. / Immunocompetent cells, participating in defense reactions of cell-mediated and humoral immunity
Normal physiology / Interaction of nervous, endocrine and immune system for functional and structure homeostasis maintaining / On practical classes determine interaction of nervous, endocrine and immune system.
Pathological anatomy / Role of immune disorders in mesenchymal and protein dystrophies, mucous and fibrinoid degeneration of connective tissue / Determine mesenchymal and protein dystrophies, mucous and fibrinoid degeneration of connective tissue. Types of tissue reactions in collagenoses.
Microbiology, virusology / Specific and non-specific mechanisms of defense. Types of antigenes, immunity, allergies. / Perform agglutination test, Coombs' test, precipitation. Titration of complement, bacteriolysis and haemolysis tests, immunofluorescence test
Propedeutics of internal diseases / Role of immune system in pathogenesis of different diseases. / Interpretation of rosette test, Manchini immunoglobulins, phagocytic activity of blood.
6. Student has to know:
1. Define “immunity”, factors of innate and adaptive immunity.
2. Main data about immune system structure and function.
4. Characteristics of phagocytosis, complement system, T- and B-lymphocyte systems, scheme of main stages of immune response.
Study questions.
1. Characterize antiviral immunity development.
2. Characterize antibacterial immunity development.
3. Characterize immunity development in case of autoimmune disorders.
4. Characterize antifungal immunity development.
5. Point indications for immunological investigation.
6. Characterize immune state of patient.
7. Estimate results immunological tests of I and II level in different conditions.
Main part
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly.
There are two groups of immune system organs.
Primary (central)--organs where immature lymphocytes develop
Thymus
Bone marrow
Secondary (peripheral)--tissues where antigen is localized so that it can be effectively exposed to mature lymphocytes
Lymph nodes
Appendix
Peyer's Patches (of GI tract)
Tonsils
Adenoids
Spleen
MALT (Mucosal-Associated Lymphoid Tissue)
GALT (Gut-Associated Lymphoid Tissue)
BALT (Bronchial/Tracheal-Associated Lymphoid Tissue)
NALT (Nose-Associated Lymphoid Tissue)
VALT (Vulvovaginal-Associated Lymphoid Tissue)
The Cells of the Immune System
T-Cells -- T lymphocytes are usually divided into two major subsets that are functionally and phenotypically (identifiably) different. The T helper subset, also called the CD4+ T cell, is a pertinent coordinator of immune regulation. The main function of the T helper cell is to augment or potentiate immune responses by the secretion of specialized factors that activate other white blood cells to fight off infection.
Natural Killer Cells -- Natural killer cells, often referred to as NK cells, are similar to the killer T cell subset (CD8+ T cells). They function as effect or cells that directly kill certain tumors such as melanomas, lymphomas and viral-infected cells, most notably herpes and cytomegalovirus-infected cells. NK cells, unlike the CD8+ (killer) T cells, kill their targets without a prior "conference" in the lymphoid organs. However, NK cells that have been activated by secretions from CD4+ T cells will kill their tumor or viral-infected targets more effectively.
B Cells -- The major function of B lymphocytes is the production of antibodies in response to foreign proteins of bacteria, viruses, and tumor cells. Antibodies are specialized proteins that specifically recognize and bind to one particular protein that specifically recognize and bind to one particular protein. Antibody production and binding to a foreign substance or antigen, often is critical as a means of signaling other cells to engulf, kill or remove that substance from the body.
Granulocytes or Polymorphonuclear (PMN) Leukocytes -- Another group of white blood cells is collectively referred to as granulocytes or polymorphonuclear leukocytes (PMNs). Granulocytes are composed of three cell types identified as neutrophils, eosinophils and basophils, based on their staining characteristics with certain dyes. These cells are predominantly important in the removal of bacteria and parasites from the body. They engulf these foreign bodies and degrade them using their powerful enzymes.
Macrophages -- Macrophages are important in the regulation of immune responses. They are often referred to as scavengers or antigen-presenting cells (APC) because they pick up and ingest foreign materials and present these antigens to other cells of the immune system such as T cells and B cells. This is one of the important first steps in the initiation of an immune response. Stimulated macrophages exhibit increased levels of phagocytosis and are also secretory.
The Immune Response
An immune response to foreign antigen requires the presence of an antigen-presenting cell (APC), (usually either a macrophage or dendritic cell) in combination with a B cell or T cell. When an APC presents an antigen on its cell surface to a B cell, the B cell is signaled to proliferate and produce antibodies that specifically bind to that antigen. If the antibodies bind to antigens on bacteria or parasites it acts as a signal for PMNs or macrophages to engulf (phagocytose) and kill them. Another important function of antibodies is to initiate the "complement destruction cascade." When antibodies bind to cells or bacteria, serum proteins called complement bind to the immobilized antibodies and destroy the bacteria by creating holes in them. Antibodies can also signal natural killer cells and macrophages to kill viral or bacterial-infected cells.
Components of the immune systemInnate immune system / Adaptive immune system
Response is non-specific / Pathogen and antigen specific response
Exposure leads to immediate maximal response / Lag time between exposure and maximal response
Cell-mediated and humoral components / Cell-mediated and humoral components
No immunological memory / Exposure leads to immunological memory
Found in nearly all forms of life / Found only in jawed vertebrates
Both innate and adaptive immunity depend on the ability of the immune system to distinguish between self and non-self molecules. In immunology, self molecules are those components of an organism's body that can be distinguished from foreign substances by the immune system. Conversely, non-self molecules are those recognized as foreign molecules. One class of non-self molecules are called antigens (short for antibody generators) and are defined as substances that bind to specific immune receptors and elicit an immune response.
Adaptive immunity
The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is "remembered" by a signature antigen. The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by "memory cells". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it.
Lymphocytes
The cells of the adaptive immune system are special types of leukocytes, called lymphocytes. B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow. B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response.
Both B cells and T cells carry receptor molecules that recognize specific targets. T cells recognize a “non-self” target, such as a pathogen, only after antigens (small fragments of the pathogen) have been processed and presented in combination with a “self” receptor called a major histocompatibility complex (MHC) molecule. There are two major subtypes of T cells: the killer T cell and the helper T cell. Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells only recognize antigens coupled to Class II MHC molecules. These two mechanisms of antigen presentation reflect the different roles of the two types of T cell. A third, minor subtype are the γδ T cells that recognize intact antigens that are not bound to MHC receptors.
B lymphocytes and antibodies
A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides. The B cell then displays these antigenic peptides on its surface MHC class II molecules. This combination of MHC and antigen attracts a matching helper T cell, which releases lymphokines and activates the B cell. As the activated B cell then begins to divide, its offspring (plasma cells) secrete millions of copies of the antibody that recognizes this antigen. These antibodies circulate in blood plasma and lymph, bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes. Antibodies can also neutralize challenges directly, by binding to bacterial toxins or by interfering with the receptors that viruses and bacteria use to infect cells.
Antibodies or Immunoglobulins
Definition:Glycoprotein in serum and tissue fluid
* Produced by:B-lymphocytes in response to exposure to antigen
* React specifically with antigen
* Five classes of Antibodies:IgM, IgG, IgA, IgD, IgE
Antigens
- Epitope - The distinct molecular surface features of an antigen capable of being bound by an antibody (a.k.a. antigenic determinant). Antigenic molecules, normally being "large" biological polymers, usually present several surface features that can act as points of interaction for specific antibodies. Any such distinct molecular feature constitutes an epitope. Most antigens therefore have the potential to be bound by several distinct antibodies, each of which is specific to a particular epitope. Using the "lock and key" metaphor, the antigen itself can be seen as a string of keys - any epitope being a "key" - each of which can match a different lock. Different antibody idiotypes, each having distinctly formed complementarity determining regions, correspond to the various "locks" that can match "the keys" (epitopes) presented on the antigen molecule.
- Allergen - A substance capable of causing an allergic reaction. The (detrimental) reaction may result after exposure via ingestion, inhalation, injection, or contact with skin.
- Superantigen - A class of antigens which cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release.
Cytokines
Low molecular weight soluble proteins (polypeptides) produced in response to microbes and other antigens
They act via cell surface receptors to mediate and regulate the amplitude and duration of the immune-inflammatory responses, through activation of macrophages, controlling growth and differentiation of T and B cells
Interferons (IFNs)
Interferons (IFNs): are proteins secreted in response to viral infections or other stimuli
* They include:
- INF-α produced by leucocytes induced by virus infected cells
- INF-β produced by fibroblasts
- INF-γ produced by NK cells,TH1 cells, CD8 T-cells
Major Histocompatibility Complex (MHC)
The MHC is a closely linked complex of genes that govern production of the major histocompatibility
* In humans, MHC resides on the short arm of chromosome 6
MHC Class I Antigens
* Class I MHC antigens are : HLA-A, HLA-B and HLA-C
* These antigens are glycoproteins found on surfaces of all nucleotide human cells and on platelets
MHC Class II Antigens
Class II antigens are: HLA-DP, HLA-DQ, HLA-DR antigens
These antigens are glycoproteins found on the surface of macrophages, B-cells, Dentritic cells, Langerhans cells of skin and activated T cells
3. Final part Test-control
Initial knowledge level
1. Which of the following is a major interleukin produced by CD4+ T helper 1 (TH1) lymphocytes?
A. IL-1
B. IL-2
C. IL-4
D. IL-6
E. IL-8
2. Which of following are presented in association with antigens processed by the exogenous antigen presentation pathway?
A. Fc receptors
B. IgG heavy chains
C. MHC class I molecules
D. MHC class II molecules
E. T cell receptor (TCR)
3. Which of the following events occurs first in the differentiation sequence of human B cells in the bone marrow?
A. Cytoplasmic mu chains present in the B cell
B. Immunoglobulin heavy chain rearrangement
C. Immunoglobulin light chain rearrangement
D. Surface IgD and IgM present on the B cell
E. Surface IgM present on the B cell
4. Which of the following is the most important costimulatory signal provided to a T cell from an antigen-presenting cell?
A. B7 molecules interacting with CD 28
B. B7 molecules interacting with LFA- 1
C. ICAM-I interacting with LFA-1
D. LFA-3 interacting with CD 28
E. MHC class II interacting with T cell receptor
5. Cytotoxic T cells induced by infection with virus A will kill target cells
A. from the same host infected with any virus
B. infected by virus A and identical at class I MHC loci to the cytotoxic T cells
C. infected by virus A and identical at class II MHC loci to the cytotoxic T cells
D. infected with any virus and identical at class I MHC loci to the cytotoxic cells
E. infected with any virus and identical at class II MHC loci to the cytotoxic cells
6. Which of the following genes involved in the synthesis of immunoglobulins are linked on a single chromosome?
A. C gene for gamma chain and C gene for alpha chain
B. C gene for gamma chain and C gene for kappa chain
C. V gene for kappa chain and C gene for the epsilon chain
D. V gene for lambda chain and C gene for kappa chain
E. V gene for lambda chain and V gene for heavy chain
7. What is the role of the macrophage during antibody formation?
A. Activation of cytotoxic CD8 T cells
B. Delayed hypersensitivity reaction
C. Lysis of virus-infected cells
D. Processing antigen and presenting it to T helper CD4 cells
E. Synthesis of immunoglobulin
8. which of the following complement activities would a deficiency of the complement protein C4 inhibit?
A. Completion of the classic pathway to the splitting of C3
B. Formation of C3b for opsonization
C. Formation of C5 convertase via the alternative pathway
D. Formation of C5a for chemotactic attractant for neutrophils
E. Formation of the membrane attack complex
9. A superantigen is a bacterial product that
A. binds to B7 and CD28 costimulatory molecules
B. binds to the β chain of TCR and MHC class II molecules of APC stimulating T cell activation
C. binds to the CD4 + molecule causing T cell activation
D. is presented by macrophages to a larger-than-normal number of T helper CD4 + lymphocytes
E. stimulates massive amounts of IgG synthesis because of its large size
10. The blood from an 8-year-old boy was analyzed by flow cytometry. The exact number of B cells was counted. Which of the following cell surface markers was likely used to identify the B cells in this blood sample?
A. CD3
B. CD4
C. CD8
D. CD19
E. CD56
11. Which type of cells will T cells that have a low affinity for MHC class I molecules differentiated in the thymus become?
A. CD 8 + cytotoxic lymphocyte
B. Gamma-delta T cell
C. Natural killer cell
D. T helper 1 cell
E. T helper 2 cell
12. Which marker or markers are present on B cells and could be used to specifically identify such cells in a flow cytometric analyzer?
A. CD 3
B. CD 8
C. CD 14
D. CD 16 and CD 56
E. CD 19 and CD 20
13. Which of the following is the primary opsonin in the complement system?
A. C1q
B. C3b
C. C5
D. C5a
E. Factor B
14. Which of the following is an IgG2 molecule composed of?
A. One alpha, one gamma2, and two kappa chains
B. One gamma1 chain and two kappa chains
C. Two gamma1 chains and one kappa and one lambda chain
D. Two gamma1 chains and two kappa chains
E. Two gamma2 chains and two kappa chains
15. Avidity is important because:
- it amplifies the binding strength of low affinity Fab’s.
- Fc receptor binding depends on it.
- G-protein-mediated signal transduction will not occur without it.
- it result in the activation of high affinity antibody-producing clones.
- none of the above.
Final knowledge level
1.A researcher develops a specific antibody to the complement component C3b. Assume that intravenous administration of the antibody prevents the biological effects of C3b. Which of the following biological functions would the administration of the antibody be expected to interfere with?