Immune system Flashcards
The immune system has three types of components
– Lymphoid tissues
– Various types of immune cells
– Chemical signals that coordinate responses
The immune system is able to recognize molecules as
foreign (“non-self”) and specifically attack them
Functions of immune system
Protects against pathogens – Bacteria – Viruses – Parasites Protects against foreign molecules (e.g., toxins) • Removes dead or damaged cells • Attempts to recognize and remove abnormal cells
3 types of immune system pathologies
Incorrect immune responses – Autoimmune disease (e.g., Type 1 diabetes) • Overactive immune responses – Allergies • Lack of immune response – Immunodeficiency disease (ex: AIDS)
2 lines of defense in the organism
- Physical and chemical barriers
2. Immune defenses
Examples of physical and chemical barriers
–Skin, epithelial linings, and cilia
–Acids, mucus, and lysozymes
2 types of immune defenses
Innate and Acquired/adaptive
Differences between innate and acquired immunity
–Innate immunity
• Non-specific – responds to a range of signals
• Immediate response
–Acquired/adaptive immunity
• Specific – attacks a specific pathogen or antigen
• Slower but stronger response
• Memory allows for fast responses upon re-exposure
4 examples of chemicals that act as barriers
- sebum( secreted by sebaceous glands, low pH inhibits
microbial growth - Perspiration (flushes skin of microbes, contains lysozyme
- gastric juice (low pH, presence of enzymes)
- urine: flushes preventing attachment
What is part of our innate immunity
Epithelial
Phagocytes (activate complement and NK cells)
Complement
NK cells (a type of lymphocyte)
Cells that are part of adaptive immunity
B lymphocytes that will differentiate to plasma cells that will produce antibodies upon exposure of particular antigen
T lymphocytes , cytotoxic T cell and T helper
4 steps in an immune response
- Detection and identification of the foreign
substance - Communication with other immune cells
- Recruitment of other immune cells, and
coordination of the response - Destruction or suppression of the invader
What is a lymphatic system
a vascular system that collects tissue fluid and returns it to the blood.
This lymphatic fluid (called lymph) is monitored for pathogens by immune system cells as it travels
What in lymphatic system is packed with T and B cells
Lymph nodes
What happens to lymph after certain period of time
It is going to be dumped back into the veins and thus right atrium
How much of fluid gets into the lymph system every day?
3.6L
The flow of lymph depends on
Muscle contraction, because it has no driving force
Primary lymphoid tissues
Bone marrow
Thymus
Encapsulated lymphoid tissues
Lymph nodes
Spleen
Lymphoid nodules are also called what type of lymphoid tissues
Diffuse, for example gut-associated lymphoid tissue (GALT) . they are found beneath epithelial
Where thymus gland is found
A 2-lobed organ located in thorax just
above heart
When thymus gland reaches its peak size and what happens after
adolescence, then shrinks and is replaced
by adipose
What cells are eliminated during the development in thymus
cells that would be
self-reactive in the thymus are eliminated
Thymus produces
T lymphocytes
- Peptides: thymosin, thymopoietin,
thymulin
what are lymphoid nodules
Loose connective tissue with densely packed
lymphocytes
• Not surrounded by a fibrous capsule
In germinal center of lymph nodules what can be found
Dividing lymphocytes
Lymphoid nodules size
Size can increase or decrease depending on number of
lymphocytes present
Where lymphoid nodules are found
Located beneath epithelial lining of organs that have
direct contact to the outside world (digestive,
respiratory, urinary
Distribution of Lymphoid Nodules
– Respiratory tract (tonsils)
– Along digestive and urinary tracts
Steps in viral invasion
Viral invasion of host cell
Synthesis of new viral
nucleic acids and proteins
Self-assembly of new viral
macromolecules into new
virus particles
Virus particles released
from host cell
What is interferon
A chemical that will be released from virus infected cells.
It will warn nearby cells and induce the production of antiviral protein (AVP)
Anatomy of lymph nodes
Will have multiple afferent lymph vessels coming to the germinal core, screens and then the fluid goes out through efferent vessel. Has lymph node artery and vein
B cells are around the cortex
then t cells (paracortical) and medullary cords are macrophages and plasma cells
Anatomy of spleen
Darker regions of red pulp
are closely associated with
extensive blood vessels and
open venous sinuses.- associated with RBCs
Regions of white pulp resemble the interior of lymph nodes and are composed mainly of lymphocytes Located behind the stomach
Division of WBCs
Granulocytes(neutrophiles,basophules,eosinophils)
Agranulocutes (monocytes, lymphocytes,dendritic cells)
Appendix has a lot of
Lymphoid nodules
Mast cells have similar function to ___, however
Basophils
Release histamine and heparin
Mast cells are tissue specific, when basophils are in circulation
What kind of cells are highest in population in blood and their function
Neutrophils
Ingest and
destroy
invaders
Eosinophils function
Destroy invaders, particularly antibodycoated parasites
Function of monocytes and macrophages
Ingest and destroy
invaders.
Antigen presentation
What cells are a link between innate and adaptive immunity, their other name and function
Dendritic cells Also called Langerhans cells, veiled cells Recognize pathogens and activate other immune cells by antigen presentation
Lymphocytes and plasma cells function
T, B, NK cells
Specific responses
to invaders, including
antibody production
Types of macrophages (brain,lungs,spleen,kidney, liver, epidermis)
Microglial Alveolar Macrophages in sinuses of spleen Macrophages in kidney Kupffer cell Dendritic cells Macrophages in joints
Natural cells are good at
Releasing granules that kill some virus-infected cells and abnormal looking cells
Why most pathogens do not enter the body
they are kept out by surface tissues and their secretions: • Physical barriers – Skin – Mucous membranes • Chemical barriers – Stomach acid – Lysozyme in many secreted fluids
What is done to pathogens without capsule
Phagocytosis by phagocytes
What is done to pathogens with capsules
antobody molecules are attached to the pathogen. then the phagocyte with these antibody receptor recognizes it ->phagocytosis
Ingested pathogens are ___ in phagocytes
Are killed by lysosomal enzymes
Dendritic cells role
They reside in peripheral tissues
Dendritic cells migrate via lymphatic vessels to regional lymph nodes
Mature dendritic cells active naive T cells in lymph nodes by presenting an antigen
How antigen presentation happens
Pathogen is lyzed and then macrophage presents antigen fragments on the surface receptor
What NK cells secrete
Interferon-alpha and interferon-beta
• Prevent viral replication
– Interferon-gamma
• Activates macrophages and other immune cells
Inflammation is caused by
Infection or tissue damage stimulates a set of
local nonspecific reactions
3 beneficial roles of inflammation
Attract immune cells and chemical mediators to
sites of infection
– Create physical barriers to prevent infections from
spreading
– Promote tissue repair
Steps in the inflammation response
Chemical signals called cytokines are released upon tissue
damage or infection
-Acute-phase proteins help prevent tissue damage
• Cytokines stimulate histamine release from mast cells
Histamine causes ____
- vasodilation->leads to heat and redness
- nearby capillaries become more permeable
2a - wbc’s and plasma proteins move into tissue
2b - edema (swelling) results from the osmotic
effect of the plasma proteins
Cytokines aree
small proteins that stimulate or
inhibit many normal cell functions such as cell
growth and differentiation
• Released by tissue macrophages to stimulate
inflammation
• Attract other immune cells, increase tissue
permeability, and cause fever
Interleukins are
a subset of cytokines
– Cause fever, blood vessels become more permeable to
wbc’s and proteins, acute-phase proteins
Other chemicals released during inflammation
Bradykinin
– Pain and swelling
• Complement proteins (inactive as plasma
proteins)
– Complement cascade produces a membrane attack
complex (MAC) that inserts into foreign cell
membranes and results in cell lysis
Acute phase proteins function
Liver proteins that act as opsonins (any molecule that enhances phagocytosis by marking an antigen) and enhance the inflammatory response
What are chemotaxins
Molecules that attract phagocytes to a cite of infection
What are pyrogens
Fever-producing substances
What is an acquired immunity
response reacts to and targets a
specific foreign molecule, called an antigen
What is active immunity
occurs when the lymphocytes are exposed
to foreign antigens in the body, (vaccination or exposure to the disease)
What is passive immunity
Passive immunity occurs when we receive antibodies made
elsewhere (breast feeding
Cytokines regulate both___
innate and acquired immune
responses, and also help coordinate these responses
What is the problem with passive immunity
we do not acquire memory cells
The coarse of the adaptive response
1. Antigen presentation to helper T cell by either a B cell or APC 2. The helper T cell gives the B cell permission to differentiate into a plasma cell 3. Plasma cell (activated B cells) 4. Which produces antibody against the antigen that was presented.
What happens at the infection site after producing antibodies
On the cellular reaction side, T cells identify infected cells through MHC antigen complexes on their surface and become activated B. The helper T cell produces cytokines that cause the activated T cell to differentiate into a cytotoxic T cell which then kills the target cell C. B cells and cytotoxic T cells become memory cells
Differences in types of lymphocytes
B lymphocytes – Plasma cells àsecrete antibodies • T lymphocytes – Helper T cells àsecrete cytokines – Cytotoxic T cells àdirectly attack infected cells • NK cells
What is the majority if circulating lymphocyte and what they are part of
T Cells (part of specific immunity) – Make up 80% of circulating lymphocytes
4 types of T cells
Cytotoxic T cells
– Helper T cells
– Suppressor T cells
– Memory T cells
B cells are part of ___ immunity
Specific
Percentage of B cells in lymphocytes
10-15 %
What is antibody-mediated immunity
A chain of events that destroys the target compound or organism
NK cells are part of ___
Non-specific immunity
NK cells: the other name, percentage, responsibilities
Also called large granular lymphocytes
– Make up 5% to 10% of circulating lymphocytes
– Responsible for immunological surveillance
– Attack foreign cells, virus-infected cells, and cancer cells
Where lymphocytes come from
In the bone marrow , there are hemocytoblasts. They differentiate into lymphoid stem cells. Some of them go to Thymus. Under the influence of thymic hormones lymphoid stem cells produce mature T cells
Other part of lymphoid stem cells int he bone marrow will differentiate into B cells and NK cells
Lymphocytes that all bind a particular antigen
are called a ___
Clone
What happens in immunity since Antigen stimulates a specific lymphocyte clone of cells
that have surface receptors for the antigen
Clonal expansion occurs as the cells multiple rapidly in
response to antigenic stimulation
• Some new cells become one of three types of effector
cells (plasma cells, helper T cells, cytotoxic T cells)
• Other cells become memory cells, which create a
stronger and more rapid response to future antigen
exposure (memory T helper, memory T cytotoxic,
memory B cells)
What is the role of memory cells
Respond Quickly and More
Strongly to Later Antigen Exposure (secondary immune response). It multiplies more rapidly
B lymphocytes are responsible for
Humoral immunity
Each clone of plasma cells produces a specific ___
Antibody
Antibody structure
Fc region- the base
Fab region- 2 “hands”
Fc region has 2 heavy chains that extend to Fab region as well
Fab region has also light chain
Hinge region - a connection between Fab and Fc regions- allows movement of the arms
Difference in primary and secondary responses
Primary- the peak of antobodies is day 2 and the concentration is not so high
Secondary- the response is less than a day and reaches max in day 3, but very high since the beginning
Antibodies are also known as
Gamma globulins
5 classes of antibodies
IgG,A,E,M and D
what do each of antibodies do
IgG - most common, secondary response is IgG
– IgA - secretory form (saliva, tears, breast milk, etc.)
– IgE - involved in allergic responses
– IgM - antibodies involved in primary response
– IgD - found on surface of B cells, role unclear
Functions of antibodies in general
Active B lymphocytes
Acts as opsonins ( tag antigens for phagocytosis)
Causes antigen clumping and inactivation of bacterial toxins
Activates antibody-dependent cellular activity (NK or eosinophil)
Triggers mast cell degranulation
Activates complement
In cell-mediated immunity role of T cells
T lymphocytes are
specialized to defend against intracellular
pathogens
T cells use ___ signaling
contact-dependent
What is MHC
major histocompatibility complex
Antigen-Presenting molecules and markers of ‘self’
They are found in all body cells. (MHCI)
MHC class II proteins
– Found only on antigen-presenting cells (dendritic cells,
macrophages, B cells)
– Recognized by helper T cells (CD4 T cells)
How T cells get activated
MHC -antigen complex binds to the corresponding T-cell receptor and activates T-cell with this receptor
Difference and similarities between cytotoxic T cells and helper T cells
they both mature in thymus Cytotoxic can kill directly. Target MHC class I target cells ( so any type of cells in the body)
Helper T cells binds to MHC-II antigen-presenting cells and after start secrete cytokines that will activate other immune cells
What is the reason for tissue rejection
MHC
Difference of B cells and T cells in antigen recognition
B cells can recognize and bind to antigens in lymph, interstitial fluid, or blood plasma • T cells only recognize fragments of antigenic proteins that are processed in a certain way
How antigen presentation occur
In antigen processing, antigen proteins are broken down into peptide fragments that then associate with MHC molecules • The antigen-MHC complex then inserts itself into the plasma membrane of a body cell
Cytotoxic T cells: characteristics and function
Display CD8 (CD8 T cells)
– Attack and destroy infected cells in two ways
• Release perforin to create holes in infected cells
• Stimulate apoptosis (cell suicide)
Helper T cells: function and what cd
– Secrete cytokines that influence other immune
cells
– Bind to B cells, promoting differentiation to
plasma cells
– Display CD4 (CD4T cells)
What is CD in immunity
The cluster of differentiation (also known as cluster of designation or classification determinant and often abbreviated as CD) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophenotyping of cells.
What reacts more quickly and what stronger in immune system
– Innate responses act quickly
– Acquired responses take longer, but are stronger
What chemicals coordinate and reinforce the two sets of responses
Cytokines
Immune response to extracellular bacteria
- Activity of complement system: activated by
components of bacterial cell wall - Activity of phagocytes: if uncapsulated,
macrophages can begin to ingest bacteria
immediately; presence of capsule disguises bacteria
from macrophage receptor - Role of acquired immune response (lymphocytes)
- Initiation of repair; recruitment of platelets and
proteins of coagulation cascade; once bacteria are
removed , repaired by growth factors and cytokines
Bacteria activate ___
Complement proteins
Complement proteins do what upon activation by bacteria
Make Membrane attack complex
Activate mast cells that will secrete chemotaxins and histamine
And also they will serve themselves as chemotaxins to attract circulating leukocytes
Immune response to viruses
- Antibodies act as opsonins; coating viral particles to make them better
targets for APCs such as macrophages - Macrophages that ingest viruses insert fragments of viral antigen into
MHC-II molecules on membrane; macrophages secrete cytokine
(interferon production) - Helper T cells bind to viral antigen on MHC-II molecules; activated Th
cells then secrete cytokines to stimulate B lymphocytes and cytotoxic T
cells - Previous exposure to the virus can create memory B lymphocytes with
viral antibody on their surface; activates more memory cells and
promotes development of plasma cellsàantibody production - Tc cells use viral antigen –MHC-I receptors with antigen, they secrete the
contents of their granules onto cell surface. Perforin molecules insert
pores into host cell membrane allowing granzymes to enter; cell
undergoes apoptosis
Mechanism of allergic reaction
First exposure: allergens ingested and processed by antigen-presenting cell
Antigen -presenting cell activates helper T cell, which in turn activate B lymphocyte , thus will antibodies and memory cells produced
Reexposure:allergens will bind to antibodies (IgE) on mast cell and degranulate releasing cytokines, histamine->vasodilation, bronchoconstriction and increased vascular permeability
Allergen will also bind to IgG-> activation of complement proteins-> inflammation
T cells will be activated once again ( out of memory T cells) -> release of cytokines->inflammation
Autoimmune disease in thyroid glans
Grave’s (TSH receptor on thyroid cells)
Autoimmune disease of pancreas
T1DM ( beta cells in pancreas)
Autoimmune disease in nervous system
Multiple sclerosis (myelin of CNS neurons) Myasthenia gravis (acetylcholine receptor of motor endplate) Guillain-Barre( myelin in peripheral nerves)
What is rheumatois arthritis and systemic lupus erythematosus
Rheumatoid arthritis- autoimmune , attacks collagen
systemic lupus erythematosus- causes inflammation in connective tissues, such as cartilage and the lining of blood vessels, antbodies produced against intracellular nucleic acid protein complex
What is the hygiene hypothesis
the decreasing incidence of infections in western countries and more recently in developing countries is at the origin of the increasing incidence of both autoimmune and allergic diseases.
