introduction to immune responses Flashcards
What is the immune response?
comprises an interacting network of cells and molecules responsible for mounting an immune response when appropriate
What is the function of the immune response? (3)
protect the body against invasion by microorganisms
stopping tumour formation
fight against infection
Physical barriers to infection
4 groups
Skin Mucosal surfaces mucus cilia secretions Commensal organisms - competition Acid – kills infectious agents
Skin
what does it do?
how do organisms overcome it?
Skin provides a protective cover Organisms can overcome this barrier Cuts or damaged skin Insect bites Animal bites
mucus lining
where?
what do they do?
There are areas of the body that are not covered by skin
Mucus traps organisms
Can you name infectious agents that infect the genital tract?
what is always present in gental tract? how does this help?
what are consequence if antibitoics remove this?
Commensal organisms present in the genital tract
There is always a competition
Example; if you are treated with antibiotics that result in removing the bacteria that are normally resident in the genital tract, what are the consequences?
Less competition more likely to get infection – thrush – candida
Innate immune system: Effector cells
7 cells
Phagocytes: neutrophils, macrophages, dendritic cells
mast cells, eosinophils, basophils
natural killer (NK) cells
Phagocytes - function?
origin?
identify, ingest, destroy pathogens
origin: generated in bone marrow
Phagocytes: Macrophages
what do they start off as?
how do phagocyte kill organism?
Macrophages
They start as monocytes then they are activated in the tissue and become macrophages.
Microbe must attach to phagocyte
Ingestion initiated
Organism enters the phagocyte in a vacuole
Destroyed within this vacuole
Some phagocytes become Dendritic cells
where do they enter?
what do they do?
They enter skin, mucosa, tissues
capture microbes
phagocytosis
eliminate the microbe
Phagocytic cells -what else do they do?
Eliminating the microbe is not the only task. They present these as antigens to T cells
Do phagocytes work alone?
Phagocytes don’t work alone
They need help in attaching to and destroying organisms – mainly bacteria.
Complement helps.
What are complements?
what 3 roles do they have?
Complement are a group of proteins
Task number one is to help attachment of micro-organisms and phagocytes
They also act as an enzyme cascade system.
Enhance phagocytic function
Phagocytes
We know they Kill and They can also clear dead cells
But do they have any other roles? (2)
Produce substances that attract other cells to the site– chemotactic substances
Increasing vascular permeability – allow immune cells to get in.
Innate immunity - not just Phagocytes. What other responses? (3)
Acute Phase Proteins
C Reactive Protein (CRP)
inflammation
Inflammation – Why? (2)
Attract cells to the site.
Help killing and clearance of organisms
Interferon - what make them? function?
Many immune cells make interferons
Task – to interfere with viruses infecting other cells.
Natural killer cells
innate system - jobe?
Surveillance role
Any cell that has changed is a target for killing
Summary – innate immunity
barriers to infection?
important cells?
Barriers to infection Mucus Saliva Acid of stomach Tears Sweat Cilia Cough Organisms that compete Flushing action of urine
Phagocytes Complement C-reactive protein Other inflammatory response cytokines Interferons Natural killer cells Important points – low specificity and no memory
Adaptive Immune System
difference?
tow key cells?
B lymphocytes
T lymphocytes
Adaptive immune system - high specificity
PRIMARY LYMPHOID ORGANS (2)
Bone marrow
Thymus
Secondary Lymphoid organs (4)
Blood
Spleen
Lymph
Lymph nodes
Lymphocyte development from primary to secondary organ - what is special about the cells?
Production of >108 different cells, each with different specificity
to
1 cell = 1 specificity
Lymphocytes and antigens
what is special about the cell?
how do B-lymphocytes recognise anitgens?
how do T-lymphocytes recognise antigens?
Each cell has (slightly) different cell-surface receptor for antigen, and hence binds to different antigen
B-lymphocytes recognise antigen through immunoglobulin receptors on their surface
T-lymphocytes recognise antigen through T-cell receptors
Lymphocyte response to antigen
survival for non-dividing cells?
what do they lymphocytes do in the mean time?
what happens if they bind to an antigen?
> 10^8 lymphocytes = >10^8 different specificities in your body
the non-dividing cells – live for years
patrolling – waiting to meet the one (few) antigens their receptors bind to
when (if) their receptors bind to an antigen, they proliferate
What do B lymphocytes do?
what do they make?
two example?
how do we make correct anitbodies?
B cells make antibodies
Immunoglobulins
Two examples are;
IgM – made first
IgG – made later
We have many B cells Each with own receptor Selection of specific B cell Proliferation of clone Make correct antibodies
How do antibodies work?
2 ways they work?
example of how these two ways work?
Neutralisation
Example – coat virus with antibody – stop it entering cells
Opsonization
Coat micro-organism with antibody
Phagocytic cells have receptors for antibody
Phagocytes can now attach to the bacterium
Engulf
Kill
This is team work!
Memory of immune cells
first time vs second time?
First time we see an infectious agent we take time to respond.
Second time we meet the same agent – very quick response
We remember the enemy!
This is why we call it adaptive immunity
How do T cells work?
what do thye do? how?
Helper T cells – very helpful
help B cells make antibody
How?
When activated they release chemicals known as cytokines
Cytokines are the helpful chemicals that encourage B cells to work
Problem T cells face
what can’t they see? how does the body overcome this?
T helper cells can not see the virus on their own.
They need help to see antigens
Help provided by phagocytic cells
They phagocytose the infectious agent, destroy the virus or bacterium
But they carry the antigens and present these to T helper cells.
Team work!
T cytotoxic cells
They cannot see viruses or bacteria on their own either!
So how do they kill?
use the example of cell infected by virus to explain
significance of MHC
Cell infected e.g. virus
Virus wants to replicate
Virus proteins made inside cell
Cell cannot hide infection
Virus proteins appear on cell surface – attached to a cell protein called major histocompatibility antigen MHC
T cytotoxic cells can see MHC and virus protein together
Killing begins
