Antibodies, Antibody Diversity, and T cell Development Flashcards
What is an antigen?
Anything that can be SPECIFICALLY bound by cells of the adaptive immune system
- B cell receptor
- T cell receptor
Which cells bind in a specific manner to antigen?
B and T Cells
T/F. B cells are involved in humoral immunity whereas T cells are involved in cell-mediated immunity.
True.
What happens when B cells recognize antigen?
- antibody secretion by plasma cells (effector B cells)
2. development of immunologic memory (memory B cells)
Recognition of antigen by T cells results in what?
- T cell activation
2. Development of immunologic memory (memory T cells)
What is another name for antibody?
immunoglobulin (Ig)
What are the two forms that an antibody can be found?
membrane bound (B cell receptor) or secreted
What are the functions of antibodies?
- Antigen recognition
- Direct antigen neutralization
- Opsonization (enhances phagocytosis by phagocytes)
- Activation of the complement cascade
Which cells recognize antigen? Antigen fragment (peptide) + MHC?
B cells; T cells
What is hematopoiesis?
The generation of blood cells
___ selection involving either deletion or receptor editing mediated by ___-avidity interactions with ___ antigen.
Negative; high; self
___ selection and lineage commitment is ___-avidity interaction with ___ antigen.
Positive; low; self
B cell’s hematopoietic stem cells originate in the ___ ___ and immature B cells migrate to the ___ and eventually become ___ B-2 B cells or ___ ___ B-2 B cells.
bone marrow; spleen; follicular; marginal zone
T/F. Antibody binding alone is not sufficient to neutralize antigen.
False, it is.
How do antibodies trigger the elimination of foreign antigen?
- activation of complement leads to cell lysis
- opsonization leads to phagocytosis
- ADCC causes NK mediated cytotoxicity
What are the two fragments of an antibody?
Fab and Fc portion
Which fragment binds antigen?
Fab
Four chain structure contains 2 ___ heavy chains that spans ___ and ___. There are also 2 ___ light chains that span ___ only.
identical; Fab; Fc; identical; Fab
Match the immunoglobulin with its heavy chain:
- IgG
- IgM
- IgA
- IgD
- IgE
A. mu B. gamma C. delta D. epsilon E. alpha
- IgG – B. heavy chain gamma
- IgM – A. heavy chain mu
- IgA – E. heavy chain alpha
- IgD – C. heavy chain delta
- IgE – D. heavy chain epislon
Which immunoglobulin isotype is found in mucosal areas, saliva, tears, and breast milk to prevent colonization by pathogens?
IgA
What form is IgA found?
dimer
Which antibody functions mainly as an antigen receptor on B cells that have not been exposed to antigens?
IgD
Which Ig binds allergens and triggers histamine release from mast cells and basophils?
IgE
T/F. IgG provides the majority of antibody-based immunity against invading pathogens. It is the only antibody capable of crossing the placenta to give passive immunity to the fetus.
True.
Which Ig is expressed on the surface of B cells and in a secreted form with very high avidity?
IgM
what structure is IgM found?
pentamer
In IgG, the Fab arms are linked to the Fc by an extended region of polypeptide chain known as the ___.
hinge
What two forms do the light chains of IgG have?
kappa and lambda
How many subclasses of IgG heavy chains are there?
4 (gamma 1-4)
The hypervariable regions of the antibody are known as the ___ ___ ___.
complementary determining regions (CDR)
Where is the CDR located?
on the tip of the Fab and Fc regions of the light chain of the antibody. This is where antigen binding occurs.
There are an estimated ___ human protein-coding genes. How could our body make so many different antibodies?
20,000-25,000; VDJ rearrangement
The human ___ chain variable region is constructed from the joining of three gene segments, V (variable), D (diversity), and J (joining). The ___ chain variable gene is constructed by the joining of two gene segments, ___ and ___.
heavy; light; V; J
___ ___ is the creation of antibody diversity in the Ig repertoire through the joining of various gene segments.
combinatorial diversity
After antigen stimulation, the V, D,J genes in B cells can make ___ base changes (often at the region of ___). This is called ___ ___, which occurs to increase the ___ of antibody (affinity maturation).
single; CDR; somatic mutation; affinity
What are the two BCRs you find on a naive B cells?
IgM or IgD
T/F. Plasma cells can secrete ALL of the Ab isotypes but they can only secrete ONE form of Ab.
True.
What allows for the generation of multiple antibody isotypes with the same Ag specificity?
Class switching (isotope switching)
T/F. In class switching, some genes of the constant region are looped then cut to produce a primary RNA transcript that only expresses one form of antibody.
True.
Where do T cell mature?
thymus
Those lymphocytes that do not bind ___ through their TCR are destined to die by apoptosis. This ___ selection takes place in the ___ region of the thymus.
MHC; positive; cortical
___ selection mediated by ___-avidity interactions with self antigen takes place in the ___ region of the thymus.
negative; high; medullary
T/F. If the thymocyte TCR engages in a low-affinity interaction with a self MHC molecule on the thymic epithelial cell, it is rescued from programmed cell death and continues to mature.
True. This is known as positive selection.
T/F. If the thymocyte TCR does not engage in any interactions with peptide-MHC molecule complexes on thymic epithelial cells, it will die by apoptosis.
True. This is known as lack of positive selection.
T/F. If the thymocye TCR binds peptide-MHC complexes on a thymic antigen-presenting cell with high affinity or avidity, it is induced to undergo apoptosis.
True. This is known as negative selection.
Eater cells are also known as what?
phagocytes. This antibody marking is the process of opsonization.
