Immune 1 Flashcards
What is immunity?
protection against infections
What is the immune system?
collection of cells and molecules that are responsible for defending the body against pathogens
What is a pathogen?
organism that causes disease
What is the goal of the immune system?
- Prevent foreign substances from entering the body
- Establish immunocompetence: ability of the body to produce a robust immune response following exposure to disease-producing agents
What are the characteristics of innate immunity?
- Mediates initial protection against infections
- Nonspecific defense
- Rapidly eliminate microbes that enter host tissues
- Eliminate damaged and necrotic cells
What are the different types of nonspecific defenses for the innate immunity?
- Physical barriers: skin, mucus membrane, nasal hairs, respiratory tract cilia
- Chemical barriers: skin pH, mucous secretions, gastric acids, tears, sweat, saliva
- Effector cells: macrophages, neutrophils, NK cells
What are the main cells of the innate immune system?
macrophages, neutrophils, NK cells, dendritic cells
What are the main ways that the epithelium acts as part of innate immunity?
- physical barrier to infection
- killing of microbes by locally produced antibiotics
- killing of microbes and infected cells by intraepithelial lymphocytes
What are pathogen associated molecular patterns (PAMPS)?
Recognize general microbial pattens through pattern recognition receptors
What part of the immune system has PAMPS and DAMPS?
innate
What are damage associated molecular patters (DAMPS)?
Recognize molecules released from damaged or necrotic host cells
What is the first cell type to respond to most infections (bacterial and fungal)?
neutrophils
What type of cell usually activates neutrophils?
macrophage
What are the features of neutrophils?
- Short-lived
- Ingest and degrade dead cells, debris, tumor cells, pathogens, foreign material through phagocytosis
Neutrophil
What are the features of dendritic cells?
- Thin, membranous cytoplasmic processes
- Present antigens to T cells
- Abundant near epithelium, mucus membranes
- Help shape adaptive immune response
What is the job of a dendritic cell?
- Present antigens to T cells
dendritic cells
What are the features of a macrophage?
- Survive in extravascular tissue for long periods
- Ingest and degrade dead cells, debris, tumor cells, pathogens, foreign material through phagocytosis
- May present antigens to T cells
- Release cytokines to activate other immune cells
What is the lifespan of a macrophage?
- Survive in extravascular tissue for long periods
(months or years)
What is the lifespan of a neutrophil?
short-lived
What are the types of professional antigen presenting cells?
- dendritic cells
- macrophages
- B cells
What are the features of the natural killers cells?
- Capable of rapidly attacking and killing infected cells
- Induce cell apoptosis
- Release cytokines to activate other immune cells
How can a natural killer do its job?
- directly kill an infected cell (especially virus)
- stimulate a macrophage with phagocytosed microbes to kill itself
What is the complement system?
Collection of circulating and membrane-associated proteins important in the defense against microbes
What is the classical pathway?
activated by antibodies that bind to microbes or other antigens → component of adaptive immunity (humoral)
What is the alternate pathway?
activated when complement proteins are activated on microbial surfaces → component of innate immunity
What is the lectin pathway?
activated by mannose binding lectin binds to surface glycoproteins on microbes → component of innate immunity
What is the lectin pathway activated by?
mannose binding lectin binding to surface glycoproteins on microbes
What is the alternate pathway activated by?
complement proteins are activated on microbial surfaces
What is the classical pathway activated by?
antibodies that bind to microbes or other antigens
What two complement pathways are innate immunity?
alternate pathway
lectin pathway
What complement pathway is adaptive immunity (humoral)?
classical
All three complement pathways lead to form the…
membrane attack complex (MAC)
What does formation of the membrane attack complex (MAC) in complement lead to?
lysis of microbe
What are the functions of the complement system?
- Opsonization and phagocytosis
- Inflammation
- Cell lysis
What does opsonization and phagocytosis do in the complement system?
C3b coats microbes, promotes binding to phagocytes → microbes ingested and destroyed
What does inflammation do in the complement system?
C5a and C3b are chemoattractants for leukocytes → recruit and promote inflammation
What does cell lysis do in the complement system?
complement activation concludes with the MAC → microbial death
What are cytokines?
soluble proteins that mediate immune and inflammatory reactions (communication)
What are the functions of cytokines?
- Responsible for communication b/w leukocytes and other cells
- Most cytokines function in autocrine and paracrine actions
How are cytokines released?
- Secreted in small amounts in response to external stimuli
What cell makes IL-12 and what cells does it affect?
- released by dendritic and macrophages
- affects NK and T cells
What cell makes IFN-y and what cells does it affect?
- release by NK and T cells
- activates macrophages
What cell makes TNF and what does it affect?
- released by macrophages, T cells, mast cells
- activates endothelial cells, neutrophils, and leads to inflammation
What cells make IL-1 and what does it affect?
- released by macrophages, dendritic cells, endothelial cells, epithelial cells, and mast cells
- activates endothelial cells and leads to inflammation
What cells make chemokines and what does it affect?
- released by macrophages, dendritic cells, endothelial cells, T cells, fibroblasts, and platelets
- affects leukocytes
What innate immune response do you get from extracellular bacteria and fungi?
acute inflammatory response and complement
What innate immune response do you get from intracellular bacteria?
eliminated by phagocytes
What innate immune response do you get from viruses?
Type I interferon, NK cells
What are the types of receptors of innate immunity?
- Toll-like receptor
- Nod-like receptor
- C-type lectin receptor
What is a toll-like receptor?
plasma membrane and endosomal receptors
* Recognize lipopolysaccharide (LPS), viral and bacterial RNA/DNA
What is a nod-like receptor?
cytosolic receptors
* Recognize necrotic cell products, ion disturbances, microbial products
What is a C-type lectin receptor
plasma membrane
* Recognize fungal polysaccharides
Where are toll-like receptors located in the cell?
plasma membrane and endosomal receptor
Where are NOD-like receptors located in the cell?
cytosol
Where are C-type lectin receptors located in the cell?
plasma membrane
What are the primary lymphoid organs?
bone marrow and thymus
Where do B cells develop?
bone marrow
Where do T cells develop?
thymus
What are secondary lympoid organs?
- Sites where adaptive immunity is initiated
- Lymphocytes have contact with antigens
What role does bone marrow have in immune system?
- Produces the cells of the immune system from stem cell precursors
- Soft, spongy tissue in the medullary cavity of bones
What role does the thymus have in immune system?
- Lymphatic organ responsible for the maturation and specialization of white blood cells called T lymphocytes
- After maturation, T lymphocytes enter bloodstream and travel to secondary lymphatic sites
What is waldeyer’s ring?
Where are most lymphocytes found?
lymph nodes
What is the difference between innate and adapative immunity?
- Innate immunity: first line of defense
- Develops quickly
- Rapidly reacts against infectious pathogens
- No memory
- Adaptive immunity: specialized immunity
- Develops more slowly
- Mediates an effective defense against infections
- Memory for future encounters
What are the main effector cells of the adaptive immunity?
B and T cells
What is the function of the adaptive immune system?
- Recognizes diverse foreign substances
- Triggered when microbes pass through epithelial barriers, recognized by lymphocytes in lymphoid organs
What is an antigen?
substance that can induce an immune response
What are the two parts of the adaptive immune system?
- humoral immunity
- cell-mediated immunity
What is humoral immunity mediated by?
antibodies produced by B lymphocytes
What is cell-mediated immunity mediated by?
T lymphocytes
Where are B and T cells in the lymph node?
T cells - parafollicular region
B cells - follicular region
What are the functions of antibodies?
- Secreted into circulation and mucosal fluids
- Neutralize and eliminate microbes and microbial
toxins - Prevent infections from being established
What cell makes antibodies?
B cells
B cells make up what percent of circulating peripheral lymphocytes?
10-20%
What do B cells do?
- Recognize antigens through membrane bound IgM
- Recognize many chemical structures: soluble or cell-associated proteins, lipids, polysaccharides, nucleic acids, small chemicals
- Differentiate into plasma cells after stimulation: secrete antibodies
Where are B cells activated?
peripheral lymphoid organs
