Intro to Immune System Flashcards
implications of the role of the immune system in defense against infections
- deficient immunity results in increased susceptibility to infections, exemplified by AIDS
- vaccination boosts immune defenses and protects against infections
implications of the role of the immune system in defense against tumors
Potential for immunotherapy of cancer
implications of the role of the immune system in injuring cells and inducing pathologic inflammation
immune responses are the cause of allergic, autoimmune, and other inflammatory diseases
implications of the role of the immune system in recognizing and responding to tissue grafts and newly introduced proteins
Immune responses are barriers to transplantation and gene therapy
immune system vs immune responses
System: collection of cells, tissues, molecules
Response: coordinated action of cells and molecules
first disease to be eradicated due to vaccination
Smallpox
innate immunity
Immune response that occurs immediately - is always present to block microbe entry. Is NOT antigen specific. First line of defense.
Phagocytes: neutrophils and macrophages. Goal is to ingest a microbe to alert T cells and B cells, not to kill the microbe.
What are the characteristics of the adaptive immunity?
Cells require specific antigen recognition, expansion, activation, and involve long-lasting memory
B cells and T cells. Takes time for expansions and differentiation of lymphocytes to occur
Antigen specific
B cells
Cells manufactured in the bone marrow that create antibodies for isolating and destroying invading bacteria and viruses -> plasma cells
T cells
Cells created in the thymus that produce substances that attack infected cells in the body.
T lymphocytes -> effector T cells
humoral immunity
Functions to block infections and eliminate extracellular microbes.
B lymphocytes responding to extracellular microbes using secreted antibodies.
cell-mediated immunity
Functions to eliminate phagocytosed microbes and kill infected cells and eliminate reservoirs of infection.
Helper T lymphocytes and cytotoxic T lymphocytes function to eliminate phagocytosed microbes that can live within macrophages or intracellular microbes (viruses) replicating within infected cell, respectively.
properties of adaptive immunity
Specificity: distinguishes among millions of antigens
Mounts a larger and more effective response to repeated antigen exposures
Undergo proliferation upon activation
clonal selection
The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen.
memory response
the rapid and enhanced immune response to a subsequent encounter with a familiar antigen; an enhanced cell-mediated immune response upon subsequent exposure to the same antigen
Primary: 1-3 weeks
Secondary: 2-7 days
Your patient has been recovering from implant surgery at home and gets an infection. He leaves 2 hours from a hospital and drives there to get an IV antibiotic treatment. If he were to have a deficiency, which scenario would have the best outcome?
B. T and B cells. A response from them would take weeks anyway
Cells of innate immunity
- macrophage (primary WBC)
- natural killer cell
- dendritic cell
- neutrophil
- eosinophil
- basophil
cells of adaptive immunity
B cells and T cells (CD4+ T cell and CD8+) T cell
cells which overlap between innate immunity and adaptive immunity
T cell and Natural Killer T cell
B lymphocytes
- blood/lymphoid organs
- mediators of humoral immunity; specific recognition of antigens
- (effector function): responsible for neutralization of microbes due to antibody binding to binding sites of microbe, phagocytosis, complement activation
overall function of lymphocytes
circulate and initiate a response upon recognition of antigen - circulate from lymph node to lymph node in search of an antigen
(B and T lymphocytes)
T lymphocytes
- blood/lymphoid organs
- mediators of cell-mediated immunity; specific recognition of antigens
overall function of antigen-presenting cells
detect presence of microbes
(dendritic cells, macrophages, B cells, follicular dendritic cells)
dendritic cells
- antigen presenting cells in tissue/lymphoid organs: capture of antigens for display to lymphocytes
- initiation of T cell responses
macrophages as an antigen presenting cell
- antigen presenting cells in tissue/lymphoid organs: capture of antigens for display to lymphocytes
- effector phase of cell-mediated immunity
follicular dendritic cells
- antigen presenting cells in tissue/lymphoid organs: capture of antigens for display to lymphocytes
- display of antigens to B lymphocytes in humoral immune responses
overall function of effector cells
destroy microbes
(T lymphocytes, macrophages, granulocytes)
T lymphocyte as an effector cell
- travels from blood to infection site
- elimination of antigens through activation of phagocytes, killing infected cells
macrophages as an effector cell
- travels from blood to infection site
- elimination of antigens through phagocytosis and killing of microbes
Granulocytes
- travels from blood to infection site
- elimination of antigens through killing microbes
Helper T cells
Activate macrophages, B cells and T cells with cytokines after microbial antigen is presented by an antigen presenting cell; also causes inflammation
Regulatory T lymphocytes
suppression of immune response
maturation of lymphocytes
- common lymph precursor in bone marrow
- B cells stay in bone marrow to mature; T cells migrate and mature in the thymus
- once mature, get into the circulation and go to peripheral lymphoid organs: lymph nodes, spleen, mucosal and cutaneous lymphoid tissue
differentiation of lymphocytes
Occurs when the cell binds to antigen; happens in secondary lymphoid organs
antigen recognition -> proliferation -> differentiation
what happens if a naive cell never encounters an antigen?
Naive cells survive for weeks to months - Dies without antigen recognition eventually
what happens to an effector T cell when the antigen is eliminated?
They die
Memory cells survive for…
long periods, can be many years
proportion of memory cells with age
increase
primary immune tissues
bone marrow and thymus
secondary immune tissues
spleen and lymph nodes
tissues of the immune system
Bone marrow, thymus, lymph nodes, spleen, tonsils, adenoids, appendix, Peyer’s patch
organization of secondary lymphoid organs enables…
- antigen presenting cells to concentrate antigens
- lymphocytes to locate and respond to antigens
- cells to interact with each other
tissue with the highest number of lymphocytes
lymph nodes (190 x 10^9)
lymph nodes
Bean-shaped filters that cluster along the lymphatic vessels of the body. They function as a cleanser/filter of lymph as wells as a site of T and B cell activation
*dendritic cells pick up antigens in tissues and migrate to lymph nodes
morphology of lymph node
- B cells are
- T cells in parafollicular cortex
- antigen gets in through afferent lymphatic vessel, lymphocytes leave through vein
function of lymphatic system and lymph node
- concentrate antigens
- lymph drained into lymph nodes allowing sampling of antigens by antigen presenting cells at the site
morphology of spleen
- highly vascularized
- blood entering the spleen allowing sampling of antigens by antigen presenting cells
- T cell and B cell zone
segregation of T and B cells in the lymph node and spleen
- B cells and follicular dendritic cells are in follicles around the periphery (cortex)
- T cells and dendritic cells are outside by adjacent to follicles (paracortex)
- once activated, they migrate towards each other
- specific receptors on the T cells and B cells respond to chemokine (cytokines) which attract cells; gradient exists
- B cell zone tissue produces specific chemokine that binds to CXCR5 receptor to attract B cells; T cell receptor is CCR7
mucosal immune system
- collection of lymphoid tissues in skin, gut, and lung
- similar organization as lymph nodes (tonsils, Peyer’s patch), with zones of T and B cells
- 25% of lymphocytes reside in the mucosal lymphoid tissue so that it is ready to fight against infection
chemokine
any of a class of cytokines with functions that include attracting white blood cells to sites of infection.
Migration of T Lymphocytes
- (B cells do not need to migrate because antibodies they release enter the blood)
- activated T cells migrate in tissues to eliminate microbes
- T cells get into lymph node and get activated by antigen presenting cells, then go back into circulation into peripheral tissue where they fight infection
How does immune response to microbes occur?
- Several steps: antigen recognition, cell activation, antigen elimination
- innate immunity controls level of infection: inflammation, microbe ingestion and killing by phagocytes, antiviral mechanisms triggered if is viral infection
- adaptive immunity kicks in a few weeks later: antibodies block infection, T cells, eradicate intracellular microbes
phases of adaptive immune response
- antigen recognition - by naive T and B cells
- clonal expansion - cells dividing
- differentiation in effector cells - reaches a plateau. B cells making antibodies, T cells making cytokines or killing
- contraction via apoptosis
- surviving cells become memory cells (takes 3 weeks from start)
Immediate immunity where an intruder is recognized and they eat the intruder: monocyte and neutrophil
innate immunity
Delayed immunity, where lymphocytes possess clonally distributed receptors with fine specificity for antigens. Lymphocytes divide in response to antigens and become effector and memory cells
adaptive immunity
___ capture antigens and concentrate it in lymphoid organs where the organization allows them to present it to T cells
antigen presenting cells
___ circulate through lymphoid organs, whereas ___ cells migrate to infection site
naive T lymphocytes; effector T cells
overall function of lymphocytes
circulate and initiate a response upon recognition of antigen
T lymphocytes
overall function of lymphocytes
overall function of lymphocytes
What are the characteristics of the innate immunity?
Immediate, non antigen specific response, non memory!
(Innate immunity is always present to block microbe entry)
_______ immunity requires expansion/differentiation of lymphocytes
Adaptive
Which type of immunity is antigen specific?
Adaptive Immunity
-it can distinguish among millions of antigens
______ immunity is mediated by antibodies; extracellular microbe
Humoral
________ immunity; T lymphocytes - intracellular microbe
Cell-mediated
Recognizes microbial antigens, on microbes or host cell surface
Adaptive Immunity
What is the function of Humoral immunity
Block infections and eliminate extracellular microbes
What is the function of Cell-mediated immunity
-Elimination of phagocytosed microbes
-Kill infected cells and eliminate reservoirs of infection
What is the time frame of Primary memory response?
1-3 weeks
(this is when B cells and T cells are recognizing antigen for the 1st time)
What is the time frame of Secondary memory response?
2-7 days
(mounts larger and more effective responses to repeated antigen exposures)
Circulates and initiates response upon recognition of antigen
Lymphocytes
-B lymphocytes: mediators of humoral immunity
-T lymphocytes: mediators of cell-mediated immunity
Detects presence of microbes
Antigen-presenting cells
-Dendritic cells: initiation of T cell responses
-Macrophages: effector phase of cell-mediated immunity
Destroys microbes
Effector cells
-T lymphocytes: activation of phagocytes, killing infected cells
-Macrophages: phagocytosis and killing of microbes
-Granulocytes: killing microbes
Survive for weeks-months and die if no antigen
Naive T/B cells
Short lived and die when the antigen is eliminated
Effector T/B cells
Survive for long periods of time
Memory T/B cells
Organization of secondary lymphoid organs enables…
- Antigen presenting cells to concentrate antigens
- Lymphocytes to locate and respond to antigens
- Cells to interact with each other
Lymph draining into lymph nodes…
-Concentrates antigens
-Allows sampling of antigens by antigen presenting cells at the site
Lymph Node morphology
-Distinct B and T cells zones
-Dendritic cells (DC) pick up antigens in tissues and migrate to lymph nodes
Morphology of Spleen
-Distinct T cell and B cell zones
-Blood entered the spleen, allowing sampling of antigens by antigen presenting cells (APC)
Activated T cells migrate in tissues to eliminate ________
microbes
Mucosal Immune System
Similar organization as lymph nodes (tonsils, Peyer’s patch)
B cells are attracted in follicles around the ________ (______)
periphery (cortex)
CXCR5 binds to CXCL5
T cells are attracted outside but adjacent to ________ (________)
follicles (paracortex)
CCR7 binds to CCL19
List the phases of Adaptive Immune Responses
1) Antigen recognition
2) Clonal expansion (now cells are activated)
3) Differentiation in effector cells
4) Contraction via apoptosis (most of the cells die but some survive)
5) Memory cells (surviving cells become memory cells)
