Flashcards in Lecture 16 - B Cell Activation and Antibody Production (part II) Deck (123)
Alternating processing of a primary RNA transcript resutls in what?
The formation of mRNA for the membrane or secreted form of μ heavy chain
What does B cell differentiation results in an increasing fraction of what?
The μ protein produced as the secreted form
What are four exons of the Cμ gene?
Cμ1, Cμ2, Cμ3, Cμ4
In T-dependent responses, some of the progeny of activated IgM and IgD expressing B cells under what?
Heavy chaing isotype (class) switching and produce Abs with heavy chains of different classes
Where does isotype switching primarily occur? What are they driven by?
In the germinal centers
Driven by Tfh cells
What is another place were some isotype switching may occur? What are they driven by?
In B cells in extrafollicular foci, driven by extrafollicular Th cells
The capacity of B cells to produce different Ab isotypes provides what?
A remarkable plasticity in humoral immune responses
Abs of various classes perform distinct effector function and are involved in defense against:
Different types of pathogens
Class-switching occurs in response to changing what?
The constant regions of the heavy chains
What is the specificity of the Abs determined by ?
The variable regions
In class-switching, what remains unaltered?
The specificity of the Abs
Isotype switching in response to different types of microbes is regulated by what?
Cytokines produced by the Th cells that are activated by these microbes
What induces B cell switching to IgG?
IFN-γ produced by Th1
What induces B cell switching to IgE?
IL-4 produced by Th2
What does the response to viruses and intracellular bacteria involve? why?
IgG abs, because they block the entry of microbes into host cells and also promote phagocytosis by Mo
Intracellular pathogens activate what Th cells?
T helper cells of the Th1 subset to produce IFN-γ and IFN-γ+ Tfh cells to make more IFN-γ
The response to helminths is mainly driven by what Abs?
IgE, it particiipates in eosinophil and mast cell-mediated elimination of the helminths
What do helminths likely influence Tfh cells to differentiate into?
IL-4+ Tfh cells which produce Th2-type cytokines during the germinal center reaction
B cells in different anatomic sites switch to different ______.
B cell in different anatomic sites switching to different isotypes is controlled by what?
The cytokines produced at these sites
What do B cells in mucosal tissues switch to ?
What antibody is most efficiently transported through epithelia into mucosal secretions, where it defends against microbes that try to enter through the epithelia?
What is the switching to IgA stimulated by?
TFG-β, which is produced by many cell types including Treg and Th cells
Also BAFF, a cytokine of the TNF family
CD40 signals work together with what to induce isotype switching?
What does CD40 engagement induce?
The enzyme activation-induced deaminase (AID)
What is AID crucial for?
Both isotype switching and affinity maturation
In immunodeficiencies related to the CD40-CD40L axis, what occurs?
Ab response to protein Ag is dominated by IgM Abs, whereas there is limited switching to other isotypes
What do mature B cells first produce?
What is every C gene preceded by?
A switching (s) sequence that controls the rearrangement process