Lecture 1 - Overview of Immunology Flashcards
4 types of antigens? Examples for each.
- Pathogens: bacteria, viruses, fungi, parasites
- Molecules: proteins, polysaccharides, lipids, drugs, nucleic acids
- Transplanted organs or tissues
- Malignant cells
2 parts of the immune system? Describe each
- Central lymphoid tissue: source of immune cells => bone marrow and thymus
- Peripheral lymphoid tissue: site of antigen response => lymph nodes, spleen, tonsils, Peyer’s patches in gut, appendix, other mucosa such as the bronchial linings
Where does the transport of immune cells occur?
- Blood
2. Lymph
What is special about the role of the peripheral lymphoid tissue in the gut?
Needs to discriminate good nonself (food antigens and commensal bacteria) from bad nonself (pathogenic microorganisms)
Where is the family tree of immune cells rooted?
Bone marrow
What do white blood cells develop from?
Hematopoietic pluripotent stem cells in bone marrow
What are the 2 types of WBCs? Describe each.
- Lymphoid lineage => lymphocytes: T lymphocytes, B lymphocytes, natural killer cells, innate lymphoid cells
- Myeloid lineage => monocytes/macrophages/dendritic cells, granulocytes, mast cell precursors, erythrocytes, and megakaryocytes
Other name for granulocytes? Why?
Polymorphonuclear leukocytes because of their irregularly shaped nuclei
What are mononuclear leukocytes?
- Lymphocytes
2. Monocytes/macrophages/dendritic cells
How do lymphocytes learn to discriminate self from nonself? What is this called?
- Interaction of newly formed immune cells with other cells of the body
- Elimination of strongly binding autoreactive cells through death (deletion), anergy (made unresponsive), or suppression (held in check by regulatory cells)
- Surviving cells have no response to self => tolerant or “educated”
= EDUCATION
What are the 6 main types of immune cells and their function(s)?
- B lymphocytes => synthesize and secrete ag binding glycoproteins (antibodies)
- T lymphocytes => kill, help, regulate
- Natural killer cells => kill
- Dendritic cells and macrophages => take up and display antigens
- Neutrophils => phagocytosis
- Basophils, eosinophils, and mast cells => inflammation
How can we distinguish immune cells from each other?
- By their surface proteins: receptors for ags, signaling molecules, and adhesion molecules
- By their immune status
- By protein secretion
What are the 4 surface proteins of B lymphocytes?
- MHC
- Ig
- CD40
- BCR: B-cell receptor for antigen
What are the 4 surface proteins of T lymphocytes?
- TCR: T-cell receptor for antigen
- MHC
- CD4/8
- CD3
What are 3 types of T-lymphocytes based on their immune status? Describe each.
- Naïve T lymphocyte: prior to ag encounter, requires stronger signals to activate
- Activated, effector T lymphocyte: responding to ag
- Memory T lymphocyte: recognized ag in the past, activated more rapidly
How do immune cells communicate?
- Cell-cell interactions
2. Communication by soluble factors = cytokines
What is another name for cell-cell interactions between immune cells?
Receptor-ligand interactions
3 types of cell-cell interactions between immune cells? Provide an example for each.
- Antigen recognition: T Cell Receptor (TCR)—MHC molecule
- Adhesion: CD4/CD8—MHC
- Signaling: TCR—CD3
What is the role of the CD3 surface protein of T lymphocytes?
Help send antigen recognition signals to inside the T lymphocyte to activate it
What are cytokines? How do they work?
Hormone-like proteins secreted by a variety of cell types that bind cell surface receptors on a variety of cells to alter gene expression, causing:
- Differentiation
- Proliferation
- Activation/Inactivation
- Migration (chemokines)
What are 3 types of T-lymphocytes based on protein secretion?
- T helper 1: IFN-gamma
- T helper 2: IL-4
- T cytotoxic: perforin
Role of perforin?
Causes other cells to lyse
How do pathogens vary? What does this mean?
- Varying life cycles
- Varying sites of infection
- Extra or intracellular
- Varying mechanisms of escape from immune recognition
=> variation in types of response from immune system
3 stages of immune response?
NON-SPECIFIC (no memory):
- Exclusion
- Innate immunity
ANTIGEN-SPECIFIC (memory):
3. Adaptive immunity
Describe innate immunity.
Immune cells’ surface receptors for danger activated => acute inflammation with influx of cells and their products: phagocytic cells (macrophages, neutrophils) and antibacterial proteins
2 types of non-specific immune cells and the danger signals they respond to?
- Macrophages: microbial patterns (lipoproteins, double-stranded RNA, flagellin)
- NK cells: self stress proteins
What are the 2 possible outcomes of the innate immune response?
- Infection resolved
2. Infection continues and starts to spread => adaptive immune response takes over
2 other names for adaptive immune response?
- Specific immune response
2. Acquired immune response
4 characteristics of the adaptive immune response?
- Antigenic specificity
- Diversity
- Self regulating
- Immunologic memory
What are the 2 immune cells of the adaptive immune response?
- B lymphocytes
2. T lymphocytes
T and B lymphocytes exhibit antigen specificity - what does this mean? How is this possible?
They recognize specific targets with specific antigen receptors
Special genetic mechanisms assemble unique antigen-binding receptor genes in each B and T cells
What is a polyclonal immune response?
Response with diverse clones of T and B lymphocytes responding to the same specific antigen
Describe the immune response at the site of infection. What is this called?
Dendritic cells bind the pathogen, bring it inside, break it up, and present it on MHC surface proteins for other immune cells to recognize and be activated
= dendritic processing and presenting
What happens once the dendritic cell is activated at the site of infection?
- It receives signals to migrate to lymph nodes
- B and T lymphocytes pass through the lymph node
- Those that have a receptor for that particular antigen will bind and be activated in the LN/those that do not will keep going through
- Activation of T and B lymphocytes initiates intracellular signaling cascades resulting in gene transcription => cell proliferation, differentiation, cytokine secretion
Other name for dendritic cell?
Antigen presenting cell (APC)
What process is a target for immunosuppression?
Lymphocyte activation
What determines the types of activated lymphocytes in the lymph node?
Cytokine environment of the lymph node and class of MHC interacting with lymphocyte
What different types of T lymphocytes could be differentiated in the lymph node? Explain each’s role.
- CD8+ cytotoxic killer T cells: kill virus infected cells
- Th1: help macrophages destroy intracellular pathogens and provide help to B cells for AB production
- Th2: help innate cells (e.g., mast cell) respond to parasites and provide help to B cells for switching to IgE production
- Th17: recruit neutrophils to infection sites to respond to extracellular bacteria and promote barrier integrity
- Tfh (T follicular helper cells): help B cells make antibody (differentiate into plasma cells), isotype switching, and somatic hypermutations
- Treg (T regulatory cells): suppress immune response
+ many others
What happens once a B lymphocyte is activated in the lymph node? What is this called?
It secretes soluble antibodies specific for pathogen => humoral response
How do antibodies differ from each other?
- Half-lives
- Abilities to be secreted
- Abilities to interact with other components of the immune system
When using antibodies, what results in destruction of the pathogen?
Complement cascade: serum proteins bind to one another and/or to the antibody in a specific pathway
How is the immune response turned off when needed?
- Regulatory lymphocytes
- Inhibitory cytokines
- Inhibitory receptor-ligand interactions
Immune response to extracellular pathogen?
- IgG AB
- Complement cascade
- Phagocytosis
Immune response to intracellular pathogen?
- NK cells
2. Cytotoxic T lymphocytes
Immune response to intracellular vesicles?
Macrophages
Immune response to parasites?
- IgE AB
2. Mast cells, eosinophils, and basophils
What are 2 types of immunodeficiencies? Describe each. How do these patients present?
- Inherited: genetic
- Acquired: associated with cancer or environmental exposure
=> present with recurrent or overwhelming infections
How do some diseases challenge the immune system? 3 examples?
- Immune response suboptimal
- Evasion of immune system
- Destruction/suppression of immune system
Examples:
- Cancer
- HIV
- Malaria
What happens when the immune response is too strong? Explain.
Tissue injury due to hypersensitivity and includes responses to noninfectious agents
2 types of tissue injuries caused by an immune response? Provide examples for each.
- AB mediated: bee sting (IgE), penicillin allergy (IgG, complement), serum sickness (IgG, immune complexes, inflammation)
- T cell mediated: poison ivy (contact mediated), tuberculin test (delayed response after skin injection)
What is autoimmunity triggered by? 2 types?
Triggered by genetic and environmental factors to escape regulation
- Organ-specific
- Systemic
How can people become sensitized to tissue transplants?
- Pregnancy
2. Transfusion
3 ways we manipulate the immune response?
- Vaccination produces memory response
- Therapy by inducing immune activation or introducing immune products/cells (e.g. cancer treatment)
- Induce immune suppression (e.g. transplant, autoimmunity)
Other name for central lymphoid tissue?
Primary lymphoid tissue
Other name for peripheral lymphoid tissue?
Secondary lymphoid tissue
Role of megakaryocytes?
Produce platelets important in blood clotting
