Basics of Immunology Flashcards
Define immunology (2)
- A branch of biomedical sciences concerned with immunity or immune system
- Study of host defence against infection and disorders of the immune system
What are the organs that make up the immune system? (8)
- Bone marrow
- Spleen
- Thymus
- Tonsils
- Mucous membranes
- Skin
- Lymphatic vessels
- Lymph nodes
What are the 3 classes of immune cells? (and the names of each cell in each class)
- Lymphocytes (T-cells, B-cells, and NK cells)
- Granulocytes (neutrophils, eosinophils, and basophils)
- Monocytes/macrophages
What is innate immunity? (4)
- First line immune response (present at birth)
- Relying on mechanisms that exist before infections
- Rapid (within minutes) but non-specific
- Inflammation
What is acquired immunity? (3)
- Second line immune response
- T-cells and B-cells involved
- Developed from immunological memory
Innate immunity vs. acquired immunity. Which is adaptive, and which is non-adaptive?
Innate = non-adaptive
Acquired = adaptive
What are the cells that make up innate immunity? (7)
- Natural killers
- Dendritic cells
- Mast cells
- Neutrophils
- Basophils
- Eosinophils
- Macrophages
What do NK cells do?
Cytotoxic, kill infected cells and cancer cells
What do dendritic cells do?
Antigen-presenting, important to acquired immunity
What do mast cells do?
Rich in histamine and heparin, possess antibacterial and antiparasitic functions
What do neutrophils do?
Patrol for microbial infections and one of the first responders to the site of inflammation
What do basophils do?
Fight parasite infections and mediate allergic reactions
What do eosinophils do?
Possess antibacterial and antiparasitic functions
What do macrophages do?
Phagocytosis and present antigens along with dendritic cells
What are the pattern recognition receptors in innate immune response? (5)
- Toll-like receptors (TLRs)
- NOD-like receptors (NLRs)
- C-type lectin receptors (CLRs)
- RIG-1 like receptors (RLRs)
- AIM2-like receptors (ALRs)
What are damage-associated molecular patterns (DAMPs)? (2)
- Endogenous molecules released from damaged and dying cells during infection and inflammation, such as high mobility group box 1 protein (HMGB1) and heat shock proteins (HLPs)
- Interacting with pattern recognition receptors (PRRs)
The innate immune system can detect missing-self (mainly via NK cells). What does that mean? (2)
- Recognizing molecules expressed in healthy cells but not in infected cells/pathogens
- Inhibiting innate immune response against host cells/tissues
MHC is essential for ________ _________
acquired immunity
Where are MHC class I molecules found?
What do they do?
- Identified in all nucleated cells
- Present normal self-antigens and foreign pathogen antigens to cytotoxic T cells
Where are MHC class II molecules found?
What do they do?
- Identified in macrophages, dendritic cells and B cells
- Present foreign pathogen antigens to helper T cells
Acquired immunity - What is cell mediated immunity? (4)
- Antigen-specific cytotoxic T-cells
- Release cytokines in response to the antigen
- Do not involve antibodies
- Kill infected cells
Acquired immunity - What is humoral immunity? (4)
- B-cells
- Mediated by secreted antibodies
- Attack and neutralize antigens (such as microbes) outside cells
- Prevent microbial penetration into body cells
Describe the process of T-cell maturation (4)
- Bone marrow: hematopoietic stem cells → lymphoid progenitor cells (migrate to the thymus)
- Thymus: lymphoid progenitor cells → functional T-cells with specific markers (such as TCR, CD4 and CD8)
- CD4+ T-cells: helper T-cells, secrete cytokines to stimulate the differentiation of B cells into plasma cells
- CD8+ T-cells: cytotoxic T-cells, bind and kill infected cells and cancer cells
What activates cytotoxic T-cells?
Activated by simultaneous interactions of surface molecules between cytotoxic T cell and antigen-presenting cell (APC) → T cell proliferation
What are the first and second activation signals of cytotoxic T-cells?
- First activation signal: interaction between TCR of cytotoxic T cell and MHC I molecule of APC
- Second activation signal: interaction between CD28 of cytotoxic T cell and CD80/CD86 of APC
CD80 and CD86 are called __-___________ of T-cell activation
co-stimulators
Regulatory T cells (Tregs) are a specialized subgroup of T-cells, different from helper T-cells. What do they do? (5)
- Supress immune response
- Inhibit T-cell proliferation and cytokine production
- Maintain immune homeostasis and self-tolerance
- Prevent autoimmune disease
- Promote cancer development and progression by inhibiting
anticancer immunity within the tumor microenvironment (TME)
What do B-cells do? (5)
- Provide humoral immunity
- Recognize specific antigens and differentiate into long-lived plasma cells
- Plasma cells secrete antibodies binding to specific antigens on microbes
- Destroy microbes and block them from entering into body cells
- Some B-cells evolve into memory B-cells
What are 4 ways in which B-cells can be activated?
- Activated when B-cell receptor (BCR) binds to antigen
- T-cell dependent activation
- T-cell independent activation
- Memory B-cell activation
How do memory B-cells work? (3)
- Activated by different pathogens
- Differentiate into long-lived plasma cells to secrete antibodies
- Re-enter germinal centers (GCs) to relinquish memory B cell pool
What are the 5 classes of immunoglobulins? (antibodies)
- IgA
- IgD
- IgE
- IgG
- IgM
What is the structure of IgA? (2)
- Monomeric in serum
- Dimeric in GI tract and respiratory tract
What does IgA do? (3)
- Important first line of defence against infections
- Inhibit bacterial growth and neutralize bacterial toxins
- Neutralize viruses
What is the structure of IgD?
Monomeric
What does IgD do? (3)
- Usually co-expressed with IgM
- Activate B-cells, basophils and mast cells
- Target mucosal antigens → enhance mucosal immunity
What is the structure of IgE?
Monomeric
What does IgE do? (2)
- Mediate type I hypersensitivity
- Provide immunity against helminth infections
What is the main type of antibody in the body? What percent does it make up?
IgG –> ~75% of serum antibodies
What is the structure of IgG?
Monomeric
What does IgG do?
Bind different types of antigens such as viruses, bacteria and fungi
There are 4 subclasses of IgG, 1 through 4. What is special about these? (2)
- IgG1, IgG3 and IgG4 can cross placenta
- Newborns: having the same antibodies as mothers’ in the first 6 months of life
What is the structure of IgM?
Pentameric - largest antibody
What does IgM do? (4)
- First antibody produced for humoral immunity response
- Respond to many antigens
- Mainly produced from spleen and bone marrow
- May also present as hexamers → physiological function unknown
Monoclonal antibodies can be produced via hybridoma technology. What is that? (3)
- Fusion of B-cells and myeloma cells
- B-cells: antibody production
- Myeloma cell: longevity and reproductivity
What are the 3 complement pathways?
- Classical
- Lectin
- Alternative
