Chapter 3 The Immune System Flashcards
The immune system chapter three sections 1-6
other names for nonspecific immune system
non-adaptive
innate immunity
Innate immunity
1st and 2nd line of defense
provides rapid response to invaders
generalized response using limited number of recognition specificity (non specific attacks all invaders)
response does not improve during response or if 2nd exposure to pathogen occurs (response remains constant and the same)
2nd line of defense:
phagocytosis inflammation
1 line of defense:
barriers and chemicals of skin and mucus membrane
Other names for specific immune response
adaptive immune response
acquired immune response
Adaptive Immune Response
3rd line of defense
slow but efficient response (takes weeks to days)
variable but highly selective specificity(produces antibodies specific for invading pathogen)
improves during response and remains if 2nd exposure occurs
amazing ability of this branch of IR to distinguish one organism from another!
due to a moreTARGETED(specifie)d more focused and forceful response
3rd line of defense
part of specific immune response
consists of both humoral and cell mediated response
consists of B & T lymphocytes, macro phages, antibodies
Differences in Innate IR and Adaptive IR
Innate receptors recognize: structures shared by various groups of pathogens (TLRS)
and the alterations on human cells due to infection by pathogen (MIC-A)
Adaptive IR: Adaptive receptors recognzie THEIR SPECIFIC ANTIGEN
B Cell Receptors
T Cell receptors
BCR
B cell Receptor (part of adaptive IR)
has specificity for its Ag
TCR
*T cell Receptor (part of adaptive IR)
*Has specificity for its Ag
*TCR has an alpha and beta chain each of which has a:
*constant and variable region
*Variable region binds to Ag
*trans membrane region bind TCR to the T cell
(figure 3.1)
specificity
each B or T cell has its own unique BCR or TCR this is their specificity
Diversity
collectively there are infinite binding capabilities among all the BCR and TCRs present in a human this is their diversity
who has ADAPTIVE IR, why?
adaptive is present only in vertebrates!
because of the complexity they have the ability to devote a large part of their genome to specificity. or perhaps due to their having adaptive ir they are more successful as a species.
who has INNATE IR
many types of animals and plants
Summary of Adaptive IR verses Innate IR (features/ advantages)
Adaptive:
*can TARGET IR FORCEFULLY because it can distinguish self from non-self in a specific way
* once large # of B & T cells during IR come can be retained for long periods of time as MEMORY B AND T CELLS these work to prevent reinfection (vaccination)
Innate:
*can attack any pathogen
*useful since pathogens are forever evolving
BCR and TCR are antigen receptors
they are the recognition molecules of the adaptive IR
immunoglobulins (Ig)
another name for BCRs
Ifs are on B cell surfaces and are also secreted as antibodies (Ab)
Secreted Immunoglobulins
Antibodies
TCRs where
are bound to the T cell’s surface and are never secreted
Antigen (Ag)
anything that binds to a TCR or BCR
What are Immunoglobulins
- They are glycoprotiens formed with 2 heavy and 2 light chains
- within an Ig molecule each of the 2 heavy chains are the same and each of the 2 light are the same
- Amino terminal end
- Carboxy terminal region
glycoprotiens
- make up Immunoglobulins: formed with 2 heavy and 2 light chains
- the 2 heavy chains are the same and each of the 2 light are the same
*Amino terminal end
is the Variable Region
Carboxy terminal region
is the constant region.
Variable Region
is the Variable Region differs in amino acid sequence from one Ig to another.
*Contains the region that binds the Antigen The differences in the amino acid sequence from Immunoglobin to Immunoglobin confer their specificity (figure 3.2)
Constant region
- the amino acid sequence is ~ the same with each class of Ab,
- Carboxy terminal region
- contains sites so other cells & molecules can bind (i.e. phagocytes, mast cells and complement proteins)
Immunoglobulin/ B-cell receptor
Y shaped with two chains on each chain on the inner side of the 2 arms are the heavy chain the 2 outer on the upper arms are the light chains.
if attached to B cell then there is a trans membrane region (not present if acting as an Ig/ antibody)
the very tip of the 2 arms of the B cell receptor is the antigen binding site
the constant region includes all of the lower arm as well as the lower section of the 2 upper arms of both the heavy and light chain.
figure 3.1
T Cell receptor
II shaped always embedded in t-cell surface so all contain a trans membrane region with alpha and beta chain attachments. one of the II is the Alpha chain the other is the beta chain. following the trans membrane section upward the next region is the constant region followed by the variable region which at the tip contains the antigen binding sites.
Ig molecule (BCR)
Variable region
constant region
trans membrane region
(figure 3.2)
Trans membrane Region
anchors the Ig to the B cell
and T cell receptor to T cell
Igs are Very ________
specific!!! only bind to specific pathogen wont bind to another pathogen (i.e. antibodies/Ig made during measles infection will bind to measles virus and prevent measles reinfection but measles antibodies that were made will not bind to influenza virus. SPECIFIC )(figure 3.2)
Diversity of Ig and TCRs is generated by __________________
gene rearragnement
Gene rearrangement
*is a mechanism unique to Ig and TCR situation
Ig and TCR are encoded by _____________ called __, __, ___
gene segments, V, D, J
V,D,J gene segments
encode heavy chain of Ig and Beta chain of TCR
V & J gene segments
encode light chain of Ig and alpha chain of TCR (not continuous)
Details of Gene Rearragngement
The V,D and J segments are not continuous on the chromosome so they cannot be directly transcribed and translated
* there are multiple genes encoding different V products within a person’s genome. One gene from the V region on the Chromosome is selected
* the DNA must then break and& splice to be made into a usable gene.
(figure 3.3)
somatic recombination
process of gene rearrangement (only occurs in B and T cells) the DNA then folds to bring the two chosen genes togehte
somatic recombination process
a single V gene a D gene and a J gene are each chosen from the DNA(Germiline configureation) the DNA then folds to bring the two chosen genes togehter(somatic recombination) and then the folded part is removed and the genes are now next “pasted” next eachother to form a rearranged gene
somatic recombination process (Germiline configuration)
a single V gene a D gene and a J gene are each chosen from the DNA (since there are multiple choices for V,D,J there are millions of combinations that are possible this is where the diversity in TCR and BCR in their entirety)
somatic recombination process (rearranged gene)
and then the folded part is removed and the genes are now next “pasted” next eachother to form a rearranged gene
Junctional diversity
Diversity arises due to the imprecision of enzymes in the splicing process by the insertion or deletions of nucleotides
Combinatorial Association
adds to diversity by association of a certain heavy and certain light chain. BCR or the association of a certain alpha chain and a certain Beta chain of the TCR
Clonal Selection
when one of the naive T and B cells encounters its specific antigen as the cells curculate through the body. the antigen is detected and attached by the BCR or TCR (finding of B and T cells specific antigen then can fight against pathogen and produce more)
functional product
result of gene rearrangement mechanism (TCR or BCR of a single specificity and is expressed on the cells surface
following TCR or BCR ligation by Antigen
(this typically occurs in lymph node) then the T or B cell proliferates(differentiation )
Clonal expansion
Proliferation (differentiateinto effector cells) of the T or B cell following clonal selection
first time pathogen enters body following clonal expansion
resultes in a primary immune response
where is the adaptive IR initiated?
in the secondary lymph tissues by t cells and antigen bearing dendritic cells (DCs)
Dendritic cell maturation process
immature DCs in the tissue ingests the pathogen, which induces the BC to differentiate (mature) & migrate to the draining LN.
Mature Dendritc Cell job
no longer phagocytic but becomes a professional antigen presenting cell (APC)
APC
antigen presenting cell
since dendritic cells are present in skin…
they are the best activator of naive T cells
If innate IR can not contain infection….
*mature DC presents Antigens of pathogen to naive T cells as they pass through the LN.
*For many of these T cells , their TCR will not recognize the antigen on the dendritic cells and thus will leave LN
* A small # of T cells recognize the antigen on the dendritic cells these will remain engaged with the DCS where they will become activated to proliferate and differentiate into effector T cells
(figure 3.6)
TCRs do not directly recognize the surface molecules of a pathogen
instead TCRs recognize the antigen presented by Antigen presenting cell (mature DC) this antigen is derived from the pathogen by the APC
antigens presented by APC
are 8-25 aa long and are derived from pathogens proteins
this focuses the IR on recognizing one type of molecule (proteins)
by recognizing a small linear region from pathogen this limits the difficulties of recognizing 3D aspects of whole protein
Several Ag can be presented from same pathogen
MHC
peptide antigen complex is carried to the surface of DC and presented to T cells, if right T cell binds to specific Ag at MHC complex then the T cell stays engaged with the DC
antigen presentation by DC to a Tcell
the degraded proteins of the pathogen are bound to MHC molecules
