Ch. 16 - Immune System Flashcards
Neutrophils
Where is production/function
- Produced in bone marrow
- Functions: phagocytosis, release chemicals involved in inflammation (vasodiltors, chemotaxins, etc.)
Basophils
Where is production/function
- Produced in bone marrow
- Functions: carry out functions in blood similar to those of mast cells in tissues
Eosinophils
Where is production/function
- Produced in bone marrow
- Function: destroy mulitcellular parasites, participate in immediate hypersensitivity reactions
Lymphocytes
- Mature in bone marrow (B cells and NK cells) and thymus (T cells); activated in peripheral lymphoid organs
- Function: serve as recognition cells in scpeficic immune responses and are essential for all aspects of these responses
B cells
- Initiate anti-body mediated immune responses by binding specific antigens to the B cell’s plasma membrane receptors, which are immunoglobulins. - Upon activation, are transformed into plasma cells, which secrete antibodies.
- Present antigen to helper T cells
Cytotoxic T cells
Bind to antigenes on plasma membrane of target cells (virus-infected cells, cancer cells, and tissue transplants) and directly destroy the cells
Helper T cells
Secrete cytokines that help to activate B cells, cytotoxic T cells, NK cells, and macrophages
Regulatory T cells
Act as inhibitors on other immune cells
NK cells
- Bind directly and nonspecificially to virus-infected cells and cancer cells and kill them
- function as killer cells in antibody-dependent cellular cytotoxicity (ADCC)
Plasma Cells
- secrete peripheral lymphoid organs; differentiate from B cells during immune responses
- secrete antibodies
Macrophages
- produced in bone marrow; reside in almost all tissues and organs; differentiate from monocytes
- functions:
- phagocytosis,
- extracellular killing via secretion of toxic chemicals
- process and present antigens to helper T cells
- Secrete cytokines involved in inflammation, activation and differentiation of helper T cells, and systemic repsonses to infection or injury (acute phase response)
Dendritic Cells
Produced: almost all tissues and organs; microglia in the CNS
Function: phagocytosis, antigen presentation
Mast Cells
Produced: bone marrow; reside in almost all tissues and organs; differentiate from bone marrow cells
Function: release histamine and other chemicals involved in inflammation
Innate Immunity
Nonspecific in that the identity of the target is not recognized
Adaptive Immunity
specific in that the target’s identity is recognized
Lymphatic Vessels begin as:
Fenestrated capillaries composed of a single layer of endothelium attached to a basement membrane
What is transported through Lymphatic vessels?
Lymph (similar to plasma) is transported through progressively bigger vessels, through lymph nodes, until it reaches vena cava
Larger lymphatic vessels contain one-way valves and smooth muscle
Primary lymphoid organs
- bone marrow and thymus
- initial sites of lymphocyte development
- naive lymphocytes (have not been activated by a specific antigen)
Secondary lymphoid organs
- lymph nodes, spleen, tonsils, and lymphocyte accumulations in the linings of the intestinal, respiratory, genital, and urinary tracts.
- where the naive lymphocytes are activated to participate in adaptive immune responses
Thymus
- Flat, bi-lobed organ located in superior mediastinum above heart
- enlarges during childhood, then starts to atrophy as we enter our 20s
- each lobe is comprised of lobules held together by areolar connective tissue
- each lobe consists of a medullary region and cortical region
Bone marrow is the site of:
Leukopoiesis
Lymph nodes
follicles consisting of lymphatic and non-lymphatic cells surrounded by a network of lymphatic capillaries
- each is supplied by afferent lymphatic vessels and drained by efferent lymph. vessels
Outermost cortex of lymph nodes
B-lymphocytes, macrophages, dendritic cells
Paracortex of lymph nodes
T-lymphocytes, dendritic cells
Medulla of lymph nodes
B-lymphocytes, epithelial reticular cells
The spleen
- filters blood, stores erythrocytes, removes defective erythrocytes/platelets, recycles iron (important for fighting infection)
- lies between 9th and 11th rib on left side of body
- contains red pulp and white pulp
Red Pulp in spleen
contains macrophages, erythrocytes, platelets, granulocytes, reticular cells, fibers
Cluster of Differentiation (CD)
- numerical system for classifying proteins expressed on the surface of leukocytes
- CD antigen is protein expressed on the surface of some but not all lymphocytes
Common characteristics of Lymphocytes
contain a single, large nucleus, a small amount cytoplasm, and a wide range of proteins expressed on their surface
B lymphocytes
develop in bone marrow
T lymphocytes
begin development in bone marrow but complete it in thymus
Cytotoxic T cells (TC)
- designed to destroy virus-infected and tumor cells
- play key role in transplant rejection
- release perforin, granzymes, and granulysin
- expresses CD8 on its surface for differentiation (forms dimer and interacts with MHC 1 molecule on infected cells)
Memory T cells (TM)
carry the memory of antigen exposure after the antigen has left the body
- refers to clonal growth of a T-cell that recognizes a specific antigen
Regulatory T cells (TR)
- maintain immunological tolerance
- block T cell-mediated immune responses at the end of the response window
- also help to inhibit the activity of T-lymphocytes that recognizes self-antigens
Helper T cells (TH)
assist other lymphocytes by aiding in the maturation of B-lymphocytes into plasma cells
Natural Killer Cells
- bridge between innate and adaptive immune system
List all of the T-Lymphocytes
- T-memory
- T-helper
- T-regulatory
- T-cytotoxic
- NK cells
- Mucosal-associated invariant T-cells
- Gamma delta T-lymphocytes (in gut)
Memory B Cells
- carry the memory of previous exposure to antigen
- generated after exposure to antigen by cytokine signaling
Plasma B cells
- long-lived, non-proliferating antibody-secreting cells
- arise after exposure to antigen
Other B cell types
- plasmablasts
- follicular B cells
- Marginal zone B cells
- Regulatory B cells
- Naive B cells
Positive Selection of lymphocytes
ensures lymphocytes are able to respond to antigen
Negative selection of lymphocytes
removes lymphocytes that bind strongly to self antigens
Outcomes of Negative Selection of Lymphocytes:
- Receptor Editing: change the lymphocyte receptor so it no longer recognizes self antigens
- Anergy: change the lymphocyte so it is no longer capable of an immune response
- Apoptosis: clonal deletion and cell death
- Ignorance: continue maturation
Flow of innate immunity
Foreign threats -> physical barriers (skin, mucosal membranes, tears, saliva, stomach acid, sebum) -> chemicals, proteins, and cells (histamine, complement, neutrophils, eosinophils, basophils, NK cells, macrophages) -> stereotypic response (fever, inflammation)
Opsonin
any substance or pathogen molecule that links a pathogen to an innate immune cell such as a phagocyte
Complement
family of plasma proteins (including C3b) activated during inflammation by either the classical complement pathway (adaptive immunity) or alternate complement pathway (innate immunity); not only stimulates many of the steps of inflammation but mediates extracellular killing via the membrane attack complex.
Interferons
chemical mediators produced by virus-infected cells that stimulate the production of intracellular proteins that inhibit viral replication
Toll-like Receptors (TLRs)
evolutionary ancient proteins which recognize pathogen-associated molecular patterns (PAMPs) that are shared features of many pathogens
- present on membranes of dedritic cells, macrophages, and certain nonimmune cells
- binding of pathogen to a TLR generates intracellular signals that results in secretion of inflammatory mediators
Features of the Skin
- first line of defense against foreign threats
- epidermis: waterproof, chemically resistant to bacterial enzymes
- glands: maintain surface pH of 3-5, blocking the growth of most microorganisms
- mucosal membranes contain anti-pathogenic substances (lysozymes)
(T/F): Cytokines affect both the innate and adaptive immune systems
True
Features of Cytokines
- act in a autocrine, paracrine and endocrine manner
- produced by a broad range of immune cells
- overproduction of cytokines can lead to sickness and death
Neutrophils
- most abundant leukocyte
- first responders to site of infection
- release anti-microbial enzymes and “NETS” (neutrophil extracellular traps)
Basophils
- comprise ~1% of leukocytes
- release histamines (more permeability) at site of infection
- responsible for symptoms of allergies
Mast Cells
- release histamine (expand capillaries, more permeability), heparin (allows blood to flow faster), and other compounds
- Also responsible for symptoms of allergies
Eosinophils
- comprise ~6% of leukocytes
- release histamines
- highly effective against parasites
Features of NK Cells
- able to induce apoptosis in virus-infected and cancer cells
- release granules containing powerful proteases and perforin
- also secrete alpha-defensins (anti-microbial peptides)
- people w/ an impairment in NK cell development display a heightened incidence of blood cancer
Process of Macrophage Phagocytosis:
- macrophages drawn to site by chemotaxis
- physical interaction between macrophage and foregin threat
- macrophages produce pseudopia that extend around foreign threat
- pseudopia fuse foreign threat within a vesicle forming a phagosome
- proteases and toxic chemicals in lysosome kill foregin threat
- parts of the foreign threat are exposed on the cell surface-antigen presentation
Most complements are produced in the ________ in ____________ forms.
liver;inactive
Most complements are produced in the ________ in ____________ forms.
liver;inactive
____ separate pathways all converge to produce ____ and ____ convertase activities.
3 separate pathways all converge to produce C3 and C5 convertase activities.
The ________________ opens pores on target cells.
membrane attack complex
Inflammation is:
a stereotypic innate immune response
Features of Antigens
- antigen = anything that can trigger an adaptive immune response
- immune system recognizes epitopes - discrete sites on macromolecules
- any molecule has the ability to act as an antigen, but some are more potent than others
- proteins are most potent, followed by sugars
- common antigens: componenets of bacteria, viruses, pollen, animal dander, food, drugs
Adaptive Immunity
Functions of antibodies in adaptive immunity:
- antigen neutralization
- antigen agglutination
- antigen precipitation
- complement activation
- lymphocyte recruitment and activation
Antigen Neutralization
covering and blocking the surface of the antigen
Antigen Agglutination
clumping of antigens into larger complexes more readily recognized by macrophages
Antigen Precipitation
bringing antigens out of solution, making them more easily recognized by macrophages
Complement activation
through Fc region; leading to cell lysis and attraction of other leukocytes
Primary vs. Secondary antibody responses
- Primary phase starts with IgM, while secondary phase starts with IgG
- difference in primary and secondary response is due to presence of memory B cells in secondary response
- antibodies are more rapidly produced in secondary response
Causes of Autoimmune diseases
unknown, but may include molecular mimicry, triggering of an immune response that bypasses TH cell movement, or a deficiency in TR cells
Treatment of Autoimmune diseases
immunosuppressive drugs, removal of thymus, plasmapheresis
Examples of Autoimmune Diseases
- Celiac/IBS
- Diabetes
- Graves
- Multiple Sclerosis
- Psoriasis
- Rheumatoid Arthritis
Aging-related changes in the immune system
- tissues and organs related to immunity decrease in size and become less repsonsive to the presence of pathogens
- elderly are more likely to have to take immunosuppressive drugs for other conditions (e.g. chemotherapy for cancer)
- inability to produce and mature new T lymphocytes due to replacement of thymus tissue with adipose tissue
- fewer antibodies and memory B cells are produced, reduing vaccine effectiveness
- accumulation of damage caused by autoimmune diseases that developed earlier
