Immuno 6A: The Humoral Immune Response: Activation of B lymphocytes and production of Ab

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Which type of immunity cell mediated or humoral has the ability to recognize and combat a wider range of microbes

Humoral
(cell mediated can only recognize protein antigens)

What are the effector cells of B lymphocytes called

plasma cell

Naive B lymphocytes express two class of membrane bound antibodies, what are they

IgD and IgM

During differentiation, some B cell may begin to produce antibodies of different heavy chain isotypes which mediate different effector functions and are specialized to combat different types of microbes. What is this process called?

Heavy chain isotope switching

Repeated exposure to a protein antigen results in the production of antibodies with increasing affinity for the antigen. What is this process called

Affinity maturation

What are the three types of B cell

Follicular B cells (lymph), Marginal zone B cells (spleen), and B-1 B cells (mucosa)

What type of B cell is able to respond to protein antigens and Th cell and has high affinity, long lived plasma cells, and isotype switching

Follicular B cells

Name four improvements that a secondary response has compared to a primary response in the humoral immunity

1) Quicker reaction time
2) Increased affinity maturation
3) Increased heavy chain isotope switching
4) Larger response

Describe the general pathway of signal transduction induced by antigen cross-linking and clustering of B cell receptors

BCR associated IgAlpha and IgBeta form BCR complex. When these are brought together their ITAMs start the cascade leading to activation of transcription factors leading to B cell proliferation and differentiation

Similar to how the T lymphocytes needed costimulators, there are two second signals that the B cell needs. what are they

The complement system (specifically CD3 binding to CR2) and a toll-like receptor (TLR) (which recognizes the PAMP on the microbe)

Where do the Th cells and B cells actually meet

At the edges of the lymphoid follicles in the lymph node (remember the B cells are in the follicles and the T cells are in the parafollicular cortex) (germinal centers)

Give the steps that occur as soon as the Th cell recognizes the MHC II molecule and peptide on the B cell

It expresses CD40L which binds to CD40 and it also releases cytokines. These signals then trigger then B cell to proliferate and differentiate producing antibodies (One of the effects of the reaction is the induction of heavy chain class switching which enables the production of different antibody classes which can optimally function to combat particular microbes each in a special way

What two things trigger heavy chain class switching

Binding of CD40L to CD40 and the release of cytokines from Th cells

What is the term for the rearrangement of the DNA in IgM producing cells aided by the enzyme activation-induced deaminase (AID) which allows various Ig to be produced upon activation by CD40L and cytokines

switch recombination

Over time and with secondary and tertiary immune responses, mutations increase within the CDR regions leading to somatic hypermutation which may increase (lower Kd) the attraction of antibodies towards antigens. What is the this called

Affinity maturation

what is the term for the increased mutation rate in Ig genes

somatic hypermutations

What two classes of B cells do not need Th cells

Marginal Z B cells and B-1 B cells

What are the initial antibodies made in the primary immune response of humoral immunity

IgM

How many Ig molecules need to be brought together on the surface of a cell in order to send a signal after binding of microbe

2+

What triggers the second signal in antigen binding to B cells

C3d

What is the main Ig that provides protection against helminths (parasitic worms)

IgE

What is the major Ig that provides protection in the mucosal areas (respiratory and GI tract)

IgA

What induces the switching phenomenon in B cells allowing a change from simple IgM antibodies to all the other types

Cytokines

What are the three properties of Ab binding to T dependent Ag

Heavy chain isotope switching
Affinity maturation
Memory B cell function

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