Adaptive Immunity Flashcards
Innate immunity
nonspecific defenses against any pathogen
adaptive immunity
induced resistance to a specific pathogen
specificity
resistance to a specific pathogen
memory
body responds more quickly if exposed to pathogen a secon time
humoral immunity
B cells (B lymphocyte) produce antibodies that directly target antigens
cell-mediated immunity
activated T cells (T lymphocytes) control antibody production and can directly kill infected host cells
The immune system does not recognize the _____ microbe, but innumerable tiny ______ of it.
whole; pieces
Each small segment of an _______ that elicits an immune response is called an _____ or an antigenic determinant.
antigen; epitope
Antigen =
Anti(body) Gen(erating)
Antigen (Ag)
a substance that causes the body to produce specific antibodies or sensitized T cells
Antibodies interact with ________ or ________ ___________.
epitopes; antigenic determinants
Haptens
low molecular weight (small) compound that is not antigenic on its own; antigenic only when bound to a larger “carrier” molecule
Once the antibody is formed against a hapten, the antibody is _______ against the hapten ________ presence of the carrier molecule.
active; without
Antibodies
made in response to a specific antigen; can recognize and bind to specific antigen
Another name for an antibody is:
immunoglobulins (Ig)
Antibody Structure:
Four poplypeptide chains (2 heavy & 2 light)
Each polypeptide has a:
constant region and a variable region
constant region
same within a particular class of Ig
variable region
recognize antigenic epitope; same between arms of antibodies
The Antibody is in the shape of a Y. The Fc region is the _____ while the Fab region is the ____.
stem; arms
The Fc region:
the site that binds to the cell
Fab region:
binds to the antigen
Neutralization
antibodies prevent a virus/toxic protein from binding their target
Opsonization
a pathogen tagged by antibodies is consumed by a macrophage/neutrophil
Complement activation
antibodies attached to the surface of a pathogen cell activate the complement system
Five types of Antibodies:
IgG, IgA, IgE, IgM, & IgD
Which Ab’s are monomers?
IgG, IgD, & IgE
Which Ab’s are pentamers?
IgM
Which Ab’s are dimers?
IgA
What is the only Ab known to cross the placenta? What type of immunity is this called?
IgG; Naturally acquired passive immunity
3 functions of IgG Abs?
- enhance phagocytosis through opsonization
- Neutralize toxins (antitoxins-exotoxins) and viruses
- Activate complement through the classical pathway
IgG makes up what percentage of serum antibodies?
80%
IgM makes up what % of serum antibodies?
5-10%
3 functions of IgM antibodies?
- First Ab produced in response to infection
- Agglutinate microbes
- Activate complement through the classical pathways
IgA makes up what percentage of serum antibodies?
10-15%
Where are IgA Abs found and why?
They are found in secretions. This gives IgA Abs mucosal protection from degradation. Their presence in mucous also prevents attachment of microbial pathogens to mucosal surfaces.
What two species have the ability to produce IgA proteases (that destroy IgA antibodies)?
Haemophilus influenzae, and Streptococcus pneumoniae
What percentage of antibody serum is composed of IgD?
0.2%
Functions of IgD Abs?
Abundant on surface of B cells, and involved in signaling B cells to begin producing antibodies
What percentage of antibody serum is composed of IgE antibodies?
0.002%
3 functions of IgE abs?
- On mast cells, on basophils, and in blood
- Main antibody involved in allergic reactions
- Bind parasitic worms: antibody-dependent cell-mediated cytotoxicity
ADCC
Antibody-dependent cell-mediated cytotoxicity
When is ADCC carried out?
When a pathogen is too big to phagocytose
Steps of ADCC (2):
- Target pathogen is coated with Ab (IgE)
2. Eosinophils, macrophages, and NK cells bind Fc portion of antibodies and lyse cell
Where are B cells produced?
bone marrow
Where do mature B cells go?
lymphoid organs
What types of antibodies are on the surface of B cells?
IgD and IgM
B cell becomes _________ when the surface antibodies bind their specific epitope.
activated
What do activated B cells divide and differentiate into?
plasma cells and memory cells
All the antibodies on a particular B cell recognize/bind:
the same epitope
how many antibodies can plasma cells produce per second?
hundreds to thousands
2 features of memory cells:
- long-lived
2. rapid,enhanced immune response after later exposure to same antigen
primary response
occurs after initial contact with antigen
secondary (memory) response
occurs after second exposure
What two things can activate B cells?
T-independent antigens or T-dependent antigens
How do T-dependent antigens activate B cells?
The antigen is presented with MHC II to a T helper cell. The T helper cell then produces cytokines that activate the B cell.
How do T-independent antigens activate B cells?
They stimulate the B cell to make antibodies withOUT T helper cells. T-independent antigens have repeating units (epitopes) that can bind multiple antibodies on the surface of B cells.
2 main problems with T-independent antigens:
- No memory cells are generated
2. generally weaker immune response
class switching
B cells can produce different classes of antibodies
All antibodies produced by a specific B cell recognize:
the same epitope!!!!
self tolerance
the body does not normally make antibodies against itself
clonal deletion
harmful B cells that recognize self antigens are eliminated
How many different B cell receptors are there?
At least 10^15
The vast diversity of antibodies are encoded by:
only a few hundred genes
Somatic recombination
brings together different variable, diversity, and joining regions that make up the antibody
Antibody specificity can distinguish between _______ and minor differences in the _____ ____ sequence.
isomers; amino acid
What is it called when binding to a similar epitope occurs? (ex: cowpox & small pox)
cross-binding
What are the consequences of Antibody-Antigen binding?
agglutination, opsonization, activation of complement (classical), ADCC, Neutralization
What are humoral antibodies effective against?
circulating pathogens
What things can T cells recognize? (3)
- antigens derived from intracellular pathogens (virus/bacteria/parasites)
- “non-self” cells (tumor)
- antigens presented by MHC
What can’t T cells do?
bind free-floating antigens
MHC class I
found on all nucleated cells; markers of “self”
MHC class II
found on antigen presenting cells (B cells)
MHC molecules are involved in ______ _________
thymic selection
If a T cell binds too strongly to MHC (binding self as opposed to nonself), what happens?
It is eliminated
What percentage of T cells are eliminated through thymic selection?
95%
Surface glycoprotein CD4 is found on which T cell?
T helper
Surface glycoprotein CD8 is found on which T cell?
Cytotoxic T cell
CD4 binds to MHC class _ molecules on B cells and other Antigen Presenting Cells (APCs)
two
What is the function of Helper T cells?
assist in activation of B cells and other T cells
CD8 binds to MHC class _ molecules, which display antigens from internal pathogens.
one
2 functions of cytotoxic T cells:
- differentiate into cytotoxic T lymphocytes (CTL)
2. destroy bacteria and infected host cells
Cytotoxic T lympocytes (CTL) attack the altered self cell by:
releasing perforin and granzymes
perforin
forms pores in target cells
granzymes
induce apoptosis
NK cells are similar to cytotoxic T lymphocytes, but differ in what way?
They do not require stimulation with an antigen
NK cells kill what kinds of cells?
Cells that do not produce MHC I
How do NK cells work?
They bind the target cell and then release cytotoxic granules (perforin & granzymes)
