Specific acquired immunity Flashcards
what is one way to increase the function of phagocytes?
Through Lymphocytes
How many surface antigen receptors may lymphocytes have?
100’s to 1000’s but they are all identical on each cell
What is the capacity of antigen receptors?
1 hundred billion (10’14)
- lymphocyte diversity PREEXISTs before antigen exposure
What is the epitope?
10-20 amino acids found on the antigenic molecule that fits the lymphocytes receptor
What is a naive lymphocyte?
It is a fully differentiated cell like a T-cell which needs to bind to an antigen before become “mature”
- takes 6-12 hrs to double the number of cells with the same antigen, after exposure
What is immunological memory and its significance?
after first expansion of clones we form memory cells.
- idea is that the next time we encounter the same antigen we can overwhelm it before it becomes established
Do we have more memory B cells after exposure to an antigen?
NO
- they are just easier to activate
- no Co-stimulatory signal
- only Ag on MHC I/II
how long does it take for full activation of B and T lymphocytes?
7-10 days
1-5 days for development of memory cells
What are the two kinds of adaptive immunity?
Humoral
Cell- mediated
What is humoral immunity?
The releasing of antibdies into fluids
- fluids like blood, secretion and tissue fluids
- B cell mediated
- Idea is to protect the extracellular space
What is Cell-mediated immunity?
T cells themselves survey the surfaces of the bodys cell
- looking for ones that have parasites within them or that are dangerously change or mutated
- need to be inside tissues to have effect
Where do B cells go?
To tissues to fight infection
- memory cells to BM to release IgG
What is class I MHC?
Ag synthesized within the cell
- recognized by CD8+ T cells
- kills any cell displaying foreign Ag
- Expressed by all cells except RBC’s
- this lack could be reason for persistence of malarial parasite (Plasmodium)
What is Class II MHC?
Ag are products of phagocytosis
- recognized by CD4+ T-Cells
- On monocytes/ macs, DC, B cells, Epithelial cells of thymus
What is the purpose of the thymus?
To train the T cells not to react to “self”
What is HLA?
Human Leukocyte Antigens
- Different genes from parents will display certain Ags better/worse depending on inheritance
- can one more susceptible to inflammation
Where are mature B and T cells found?
Can be found in the blood or resident in LN’s and spleen
What is B and T cell trafficking?
Mature B and T cells traveling from one LN to another or to and from spleen.
What are lymphokines and their significance?
Re-stimulation by APC’s cause the release of these cytokines of the lymphocytes
What the kinds of T cell receptors?
yS
aB- most common- 90-95%
- they are both made by different proteins
What do aB TCR’s bind to?
MHC I and MHC II molecules only
- coupled with CD3
- CD4 + and CD8 + T-cells
what do yS bind to?
They can bind to cells without the use of MHC
- coupled with CD3
- protect the mucosal surfaces of body
- double negative T cells (lacking both CD4 and CD8)
What are the 2 types of T cells?
Helpers and Killers
What are the subtypes of Helper T-cells?
TH1 Th17 Th2 Tfh Treg - Molecular marker CD4
What is the function of TH1?
recognized Ag and make lymphokine that attracts 1000’s of Macs
- Can wipe our serious infection
- destroy transplants
What is the function of Th17?
Similar to Th1 it is focused in inflammation
- more powerful than Th1
- In placed in many serious forms of AI diseases
- protect mucosal barriers
What is the function of Th2?
Stimulates macs
- able to wall off pathogens and promote normal healing
- after pathogen killing
- important in Parasite immunity
What is the function of Tfh?
stimulated by Ag and migrate to T cell areas of LN’s in the B cell follicles
- help B cells get activated
- make M,G,E, and A antibody classes
What is the function of Treg?
Keep immune system in check by suppresing activation of Th1/Th17/Th2
What is the function of Cytotoxic T cells?
Destroy any body cell they identify as bearing foreign of abnormal Ag
- CD8
How do killer T cell kill?
Fas-Fas ligand interaction
- T cells expressing Fas Ligand bind to Fas
- Fas is a protein on a target cell that induce caspase activation and apoptosis.
What are the 2 types of selection that happen in the thymus to T cells?
Positive and Negative selection
- Mature T cells that are tolerant to self Ag’s leave thymus and settle in LN and Spleen
- Self MHC restricted
What is positive and negative selection of T cells?
Positive- T-cells must recognized MHC I or II in order to be stimulated to mature (self restricted)
Negative- T cells that recognized self antigens bound to MHC II on the thymus epithelial cells are driven to Apoptosis (tolerant of self Ag’s
How do B cells recognized Ag’s to phagocytize for destruction?
surface IgD and IgM
- release then soluble versions of their receptors called antibodies
What is a plasma cell?
a fully differentiated B cell
- protein production factory that releases soluble versions of its receptor (antibodies)
- these antibodies bind to Ag and gets neutralized
How doe B cells recognized AG?
Alone
- does not need simultaneous recognition of associated MHC molecule
- it binds then is activated to prolif and diff
what immunoglobulin with a fetus have after born if infected in the womb?
IgM
-They all healthy or unhealthy express IgG from mom
What is better at activating complement IgG or M?
IgM
What will a pathogen face when trying to enter the mucous membranes first, in terms of immunoglobulins?
IgA which is found in mucous membranes
- Then it will encounter IgM and IgG once the pathogen reaches local LN and Spleen and blood
What makes you more susceptible to Salmonella?
Splenectomy because it makes IgG and IgM which would be decreased in this case
