The Immune System Flashcards
Define: Antigen
protein (or protein sequence) recognized by an antibody
Define: Antigen-presenting Cell (APC)
large, typically dendritic cell that recognizes foreign cells/materials, internalizes and digests them (into small fragments), and presents the resulting antigens to effector immune cells
fragments are presented on the surface by MHC
EX: macrophages
Define: CD Marker
cell surface protein that acts as a marker for a class of cells
CD → cluster of differentiation
Define: B Cells
make antibodies
named after the bursa Fabricius → a structure found in birds where lymphocytes differentiate → when destroyed, birds could not make antibodies
produced/mature in in bone marrow
travel through blood (lymphocytes)
Define: T Cells
named after the thymus, found in mammals and birds → when removed shortly after birth, animals cannot mount cell-mediated immune responses
produced in bone marrow
mature in thymus
travel through blood (lymphocytes)
What is the function of the immune system?
protection
What does the immune system require?
Adaptability
Surveillance
Rapid Response
Barrier
Define: Innate (natural) Immunity
- first line of defense
- can recognize non-self and attack it directly → can kill bacteria without the help of other things
- cytokines and complement
- phagocytic cell
- for viruses - NK cells, interferons
Define: Adaptive (acquired) Immunity
Recognizes sequences → adaptive, memory
specifically distinguishes self from non-self
anticipates non-self by random protein rearrangement
antibodies, MHC, T-Cell receptors
What are the Two Types of Adaptive Immunity?
- Humoral immunity → antibody mediated (plasma cells)
- Cell-mediated immunity → T cells, B cells, and antigen-presenting cells
Define: Complement
way for your body to deal with things without using cells
Innate Immunity in Action
- Bacterial cell surface induces cleavage and activation of complement
- complement fragment bonds to bacteria, another to an effector cell
- the complement receptor on the effector cell binds to the complement fragment on the bacteria
- The effector cell engulfs the bacterium, kills it, and breaks it down
Neutrophils and Macrophages
Acquired Immunity in Action
- During development, progenitor cells give rise to large numbers of lymphocytes, each with a different specificity (B and T cells)
- During infection, lymphocytes with receptors that recognize the pathogen are activated (random rearrangement to produce variety)
- proliferation and differentiation of pathogen-activated lymphocytes give effector cells that terminate the infection (T and plasma cells)
Components of the Immune System
- Diffuse Lymphatic
- Tissue/Nodules → MALT (Mucosa-associated lymphatic tissue), BALT (Bronchial-associated), GALT (Gut-associated)
- Lymph Nodes
- Spleen → cell production of functional cells
- Thymus → cell production of functional cells
Define: Epithelium
Forms tissues that act as barriers → mucosal linings, skin
lines free surfaces
separates from underlying tissue
Define: Mucosal Linings
Body parts exposed to things outside that isnt your skin
epithelium and lamina propria
Define: Lamina Propria
Loose CT underneath mucosal epithelium
rich in immune cells
Functions of the Integument system
- Protection (barrier) → Physical, Chemical, Pathogens, Desiccation, UV
- Thermoregulation
- Pressure and touch reception
- Excretion
- Production of vitamin D
Define: Epidermis
physical
keratinized epithelium
substantial cell-cell junctions
also has APCs
Define: Dermis
CT component
immune cells
lymph/blood vessels
Immune System Surveillance
begins at the surface
dendritic cells, T cells, macrophages, plasma cells, etc.
In epithelium (skin) and underlying CT (skin and mucosa)
Resident Cells of the Lamina Propria of Mucosa
Fibroblasts → collagen production
Macrophages → clean up, release inflammatory mediators
Mast cells → release inflammatory mediators
Plasma cells → antibody production
Migratory Cells of the Lamina Propria of Mucosa
Lymphocytes (T/B) → frequent
Granulocytes (neutrophils, eosinophils, basophils) → variable
Monocytes (immature macrophages) → found in resident tissue
Define: Macrophages
aka histiocytes (in skin)
ingest foreign matter
enhance lymphocyte activity
precursor → monocyte
phagocytosis and killing of microorganisms → activation of T cells and initiation of immune responses
resident
Define: Mast Cells
granules contain histamine/heparin
release chemotactic factors
single central nucleus → eosinophilic or basophilic granules
expulsion of parasites from body through release of granules containing histamine and other active agents
precursors mature in the spleen
Define: Plasma Cell
Mature B Cells
Make antibodies
comet shape
fully differentiated form of B cell that secretes antibodies
Define: Gut-Associated Lymphatic Tissue (GALT)
Found in → oral cavity, esophagus, stomach, small/large intestines (peyer’s patch, appendix), rectum
Define: Peyer’s Patch
white lumps in illium
large number of small lymphatic nodules in one area
Diffuse vs. Nodules
- both are the site of the initial immune response
- components
- diffuse → T/B cells travel to lymph nodes, mature, return to tissue
- plasma cells, eosinophils
- Nodules → concentrations of lymphocytes
- diffuse → T/B cells travel to lymph nodes, mature, return to tissue
Define: Primary Nodule
small lymphocytes
collection of unactivated small lymphocytes
Define: Secondary Nodule
lymphocytic proliferation in response to antigen produces larger cells that do not stain as darkly (germinal center)
differentiation of plasma cells
Define: Corona
darker staining rim
Bronchi-Associated Lymphatic Tissue (BALT)
- found in the bronchial tree
- trachea
- bronchus (bronchi)
- bronchioles (only larger ones)
- not in the alveoli (dust cells)
- Thick basement membrane → good barrier
Respiratory Epithelium
- Ciliated (C) → move bacteria away from lung
- pseudo stratified → barrier
- thick basement membrane (BM) → barrier
- Goblet Cells (G) → capture bacteria
- Highly Vascular (V) CT
Immune System Drainage System
Extracellular (interstitial) fluid exits tissue and enters thin walled vessels called lymph vessels
What is the function of the lymph nodes?
filter lymph fluid
Afferent
peripheral tissue to Lymph Nodes
pathogens from site of infection reach lymph nodes via lymphatics
Efferent
Lymph Node to blood (exit)
lymphocytes and lymph return to the blood via lymphatics
Define: Lymph Nodes
Filter Lymph to expose immune cells to non-self antigens not destroyed in peripheral tissue
encapsulated
Lymph node circulation
into lymph node from afferent vessels
out of lymph node from efferent vessel (hilum)
high endothelial venule → taller than normal epithelium (cuboidal)
Lymph enters subcapsular sinus → travels through paratrabecular sinus to medulla
Define: Lymph
protein with fluid
stains eosinophilic if retained
Clearance of Lymph
- cells in medulla recognize antigen and bind
- T cells activated by dendritic cells
- Plasma Cells activated by T cells
- Macrophages kill bacteria
Define: Hematopoiesis
Production of cells in the bone marrow
Define: Small Lymphocyte
production of antibodies (B Cells) or cytotoxic and helper functions (T cells)
Define: Dendritic Cell
Activation of T cells and initiation of adaptive immune response
Define: Natural Killer Cell
Kills cells infected with certain viruses
Define: Monocyte
circulating precursor cell to macrophage
in transit → becomes macrophage
Define: Neutrophil
granulocyte
phagocytosis and killing of microorganisms
Define: Eosinophl
granulocyte
killing of antibody-coated parasites through release of granule contents
Define: Basophil
granulocyte
controlling immune responses to parasites
Define: Megakaryocyte
platelet formation
wound repair
bone marrow only
Define: Eryhtrocyte (RBC)
oxygen transport
no immune function
Define: Lymphocytes
- B Cells
- mature into plasma cells
- T cells
- mature into T helper cells or cytotoxic/suppressor T Cells
can only differentiate with IHC
Define: Granulocytes
- Neutrophils
- WBC; bacterial phagocytosis
- Eosinophils
- anti-parasitic WBC
- Basophils
- WBC; similar to mast cells
Define: Leukocytes
in bone marrow
granulocytes
monocytes
Thymus
medulla is continuous → light staining
cortex → lobules separated by trabecula → darker staining
T cell maturation and quality control
- differentiation begins in cortex of thymus
- T cell receptor expression
- CD4 and CD8 expression
- In medulla, specialize:
- express either CD4 or CD8
- still express T cell
- Tested for Function:
- eliminate those that cannot function (positive selection)
- eliminate those that recognize self (negative selection)
- Managed by epithelioreticular cell (Hall monitors)
- macrophages to digest failures
- tag any cells that fail the selection process for destruction by macrophages
What must be expressed for T cells to leave the cortex?
must express both CD4 and CD8
What must be expressed for T cells to leave the medulla?
CD4 or CD8
only needs one
What happens if the T cells don’t express the requirements to leave the cortex and medulla?
they will be killed by macrophages
Define: Positive Selection
eliminate those who cannot function because they don’t properly express receptors
Define: Negative Selection
eliminate those recognize self antigens
Define: Epithelioreticular Cells
dendritic extend processes
keep an eye on T cells in thymus
What is the function of T Cells?
- only recognize epitopes bound to MHC
- Responsible for cell-mediated immune response
- CD8+ cytotoxic T cells
- CD8+ suppressor T cells
- T memory cells (anamnestic response)
- rapid and intense secondary response
- second dose → feel worse
- Facilitate B cell response
- CD4+ T Helper Cells
- Produce cytokines
- induce B cells to differentiate
How do T cells kill?
release various products to promote cell death
Define: Interleukins
like hormones but at the cellular level
Similar to growth factors, but immunological
Promote leukocyte growth and interactions
Define: Interferons
Anti-proliferative and antiviral activities
stimulate cytolytic activity in NK cells. macrophages, and lymphocytes
What are the primary functions of the spleen?
- Cardiovascular (red pulp → blood)
- Remove aging RBCs
- destruction (macrophages)
- iron recycling
- Blood storage
- Remove aging RBCs
- Immune (white pulp→ immune cells)
- T and B cell activation and proliferation (forms splenic nodule)
- mast cell maturation and activation
- monitor for blood-bourne antigens (also red pulp → macrophages and APCs)
What is the function of B Cells?
formed in bone marrow
have surface immunoglobulins
express MHCII to present antigen to T helpers
promotes T helper formation (IL-12 production)
Proliferate during humoral response → B memory cells and plasma cells
facilitate amnestic response to humoral response
Define: Antibodies
part of humoral response
Bind to particular epitope → recognized as antigen
produced by mature B cells (plasma cells)
What are the 5 isotypes of antibodies?
IgG
IgM
IgA
IgE
IgB
How do antibodies work?
- bacterial toxins meet cell with receptors for toxin → antibody recognizes toxin and binds to it so it can’t bind to cell → phagocyte ingests and destroys toxin → toxin neutralized
- Bacteria in EC space → opsonization → antibody bind to bacteria → phagocyte ingests and destroys toxin
- Bacteria in EC space → opsonization → antibody recognizes and binds to bacteria + complement → phagocyte ingests and destroys toxin
What is the major function of nodules?
immune surveillance of mucosa
What are the characteristic features of nodules?
diffuse lymphatic tissue with nodules beneath epithelium
What is the major function of nodes?
filter lymph
respond to antigens in lymph
What are the characteristic features of nodes?
lymphatic sinuses
reticular meshwork
What is the major function of the thymus?
develop immunocompetent T cells
What are the characteristic features of the Thymus?
lobules
meshwork of epithelioreticular cells
hassall’s corpuscle
What are the major functions of the spleen?
filter blood
remove old RBCs
respond to circulating antigens
What are the characteristic features of the spleen?
White pulp → PALS, nodules with central artery
Red Pulp → cords and sinuses
