Immunology Physiology: Part 2 Flashcards
What are MHCs?
Protein molecules (self-antigens) on the surface of cells. They help differentiate between invaders and self
- unique to an individual
- useful in matching organ donors
Where are MHC Is found?
found on virtually all body cells (except for red cells)
Where are MHC II’s found?
found on certain cells in the immune response
What do MHCs display?
peptides, usually self antigens
What do MHC’s display in infected cells?
display fragments of foreign antigens, which help mobilize Tcells
What are B lymphocytes associated with?
(B cells)—humoral immunity
What are T lymphoctyes associated with?
(T cells)—cell-mediated immunity
Where is the bone marrow do lymphocytes develop?
shafts of long bone and vertebra
When lymphocytes mature what characteristics do they posess that make them functional?
2
- Immunocompetence– they are able to recognize and bind to a specific antigen
- Self-tolerance – unresponsive to self antigens
Where are naive (unexposed) lymphocytes exported to?
3
lymph nodes
spleen
other lympoid organs
What are peyer’s patches?
Fixed macrophages in the colon
What are the major types of APC’s?
3
- dendritic cells
- macrophages
- activated B cells
Where do T cells become immunocompetent?
B cells?
thymus
bone marrow
Antigen-activated immumocompetent lymphocytes are what kind of cells?
effector cells and memory cells
What is positive selection of a T cell?
Selects T cells capable of binding to self-MHC proteins (MHC restriction)
What is negative selection of T cells?
What does this ensure?
Prompts apoptosis of T cells that bind to self-antigens displayed by self-MHC
Ensures self-tolerance
What will happen if a B cell is self-reactive?
3 things can happen
- Are eliminated by apoptosis (clonal deletion-group of cells that are related are deleted) or
- Undergo receptor editing – rearrangement of their receptors
- Are inactivated if they escape from the bone marrow
What determines which foreign substances the immune system will recognize and resist?
Genes
Macrophages as APCs are mostly found where?
Fixed in the lymphoid organs
Dedritic cells as APCs are mostly found where?
internalize pathogens and enter lymph system to present antigens to lymphoid organs
How do T cells activate macrophages?
release chemicals that make them insatiable phagocytes and secrete bactericidal chemicals
If the anitgen provokes a humoral immune response what is produced?
antibodies
In clonal selection how do the daughter cells differentiate from the parent cell?
Through chances in DNA that have different receptor that will indentify a uniquely different pathogen
Do B cells need MHC proteins/APC?
No, they can bind directly to the antigen
After the B and T cells are selected for by the antigen what happens?
They begin replicating rapidly but with the same receptor (unlike the first round)
When the B cells and T cells are replicating to mount an immune response to the antigen they encoutnered what kind of cells do they make?
Effector cells (plasma cells)- used to fiight the pathogen right now! -this is the fate of most cells
Memory cells- used to remember the pathogen and mount/signal an even stronger/faster response next time
What do effector cells do to mount an immune response?
secrete antibodies at a rat eof 2000 per second fro 4-5 days
What are the antibodies doing in the body?
circulating in blood an dlymph and marking the antigens for destruction
Whats the lag period of the primary immune response (first time the body ever encounters an antigen?)
When are peak levels of antibodies reached?
three to 6 days
10 days then anitbody levels decline
Whats the lag period of the secondary immune respnse?
Anitbody levels peak when?
hours
two to three days. Anitbodies bind with greater affinity and remain high for weeks or months
What are the two types of active humoral immunity and give an example of each
- Naturally acquired—response to a bacterial or viral infection
- Artificially acquired—response to a vaccine of dead or attenuated pathogens
Why do vaccines fail to fully establish cellular immunological memory?
They only target one type of helper T cell
What is different about passive humoral immunity compared to active?2
- B cells are not challenged by antigens
2. Immunological memory does not occur
What are the two types of passive humoral immunity and give an example
- Naturally acquired—antibodies delivered to a fetus via the placenta or to infant through milk
- Artificially acquired—injection of serum, such as gamma globulin
- -Protection is immediate but ends when antibodies naturally degrade in the body
What are immunoglobulins?
2
- Proteins secreted by plasma cells
2. Capable of binding specifically with antigen detected by B cells
What is the general structure of an antibody?
two heavy chains and two light chains
What part of the antibody structure determines the antibody class, what the antibody can bind to, and how the antibody functions in antigen elimination?
Constant (C) region of stem
Characteristics of IgM?
2
first responder to acute infection (can be a monomer-pentamer in pic)
Characteristics of IgA?
2
- Helps prevent attachment of pathogens to epithelial cells/respiratory too
- because its found in body secretions - (dimer)
Characteristics of IgD
2
Anitgen receptor for B cells
Monomer
Characteristics of IgG
4
- Most abundant and diverse antibody in plasma
- Main antibody in primary and secondary respinses
- Passes from mother to fetus
- monomer
Characteristics of IgE
3
- Causes release of histamines
- Heightened in allergic reactions
- monomer
Antibodies inactivate and tag antigens
Statement
What is neutralization?
antibodies bind to and block specific sites on viruses or exotoxins, thus preventing these antigens from binding to receptors on tissue cells
What is aggulation?
- antibodies bind the same determinant on more than one antigen
- Makes antigen-antibody complexes that are cross-linked into large lattices
- -Cell-bound antigens are cross-linked, causing agglutination
What is precipitation?
soluble molecules are cross-linked into large insoluble complexes
–more subjectable to phagocytosis
What is complement fixation?
- cell lysis and activation of phagocytosis
- The MAIN mechanism used against cellular antigens
- Enhances the inflammatory response
What are monoclonal antibodies made of?
hybridomas
Cell hybrids: fusion of a tumor cell and a B cell
What could monoclonal antibodies be useful for?
Proliferate indefinitely and have the ability to produce a single type of antibody
Used in research, clinical testing, and cancer treatment
What kind of cells are involved un cell-mediated immunity?
T cells and CD4 and 8 cells
When activated what do CD4 T cells become?
Helper T cells
When activated what do CD8 cells become?
cytotoxic T cells
What do antibodies of the humoral response target?
Bacteria and molecules in intracellular environments
(body secretions, tissue fluid, blood and lymph)
Straight for pathogen
What do T cells of cellmediated response target?
3
- Body cells infected by viruses or bacteria
- Abnormal or cancerous cells
- Cells of infused or transplanted foreign tissue
Cells that are infected by pathogen
Endogenous antgens are processed and displayed by what?
Class I MHC proteins
Exogenous antigens are processed and displayed by what?
Class II MHC proteins
What two things have to happen for a T cell to be activated?
- Antigen binding
2. Co-stimualtion
How are dendritic cells able to obtain other cell’s endogenous antigens?
2
- Engulfing dying virus-infected or tumor cells
2. Importing antigens through temporary gap junctions with infected cells
