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BAMS > Adaptive Immunity II > Flashcards

Adaptive Immunity II Flashcards

1
Q

What are B cells

A
  • communicate with T cells
  • have a specific B cell receptor for antigens
  • B cells produce antibodies
  • clonal expansion leads to generation of two subsets
  • plasma cells are great big antibody factories
  • memory B cells are important
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2
Q

Where do B cells mature

A

Mature in bone marrow

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3
Q

Describe B cell circulation

A

Circulate in the blood and the lymph they are found in large numbers in the lymphoid organs

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4
Q

How do B cells recognise antigens

A

They recognise antigens through the B cell receptor (BCR) which is the actual antibody (lgM or lgD)

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5
Q

When B cells are activated what do they change into

A

Plasma cells - antibody factories

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6
Q

What are the three main receptors in adaptive immunity

A
  • T cell receptor
  • B cell receptor
  • Major histocompatibility complex (MHC proteins)

Multiple genes encoding each allows the development of a repertoire of receptors with wide specificity

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7
Q

What are the 5 types of immunoglobulins produced by B cells

A

LgG, lgE, lgD, lgM, lgA

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8
Q

Describe the B cell receptor structure

A

Slightly different from T cell receptors, both have variable and constant regions, they have light and heavy chains

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9
Q

Describe LgG antibodies

A

Account for 80% of all antibodies, they are responsible for resistance against many viruses, bacteria and bacterial toxins

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10
Q

Describe lgE

A

Attaches as an individual molecule to the exposed surfaces of basophils and mast cells

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11
Q

Describe lgD

A

Individual molecule on the surfaces of B cells, where it can bind antigens in the extracellular fluid, this binding can play a role in the sensitisation of the B cell involved

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12
Q

Describe lgM antibodies

A

The first class of antibody secreted after an antigen is encountered. LgM concentration declined as LgG production accelerates, the anti-A and anti-B antibodies responsible for the agglutination of incompatible blood types are lgM antibodies

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13
Q

Describe lgA antibodies

A

Found primarily in grandular secretions such as mucus, tears, saliva and semen. These antibodies attack pathogens before they gain access to internal tissues

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14
Q

What is each development stage for B cells defined by

A

Defined by rearrangements of the immunoglobulin heavy and light chain genes

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15
Q

Once in periphery B cells migrate to…

A

Secondary lymphoid organs

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16
Q

Heavy B cell chains involves rearrangement of ….

A

Variable (V), Diversity (D) and Joining (J) genes

17
Q

Light chain involves rearrangement of….

A

Variable (V) and Joining (J) genes

18
Q

What is the B cell receptor

A

lgD

19
Q

Immature B cell receptor is mainly…

A

LgM

20
Q

Mature B cells express both….

A

LgM and lgD

21
Q

Describe negative selection of B cells

A

Undergo negative selection in the bone marrow, macrophages will engulf and remove self reacting B cells

22
Q

What are the three functions for antibodies in the human body

A
  • Neutralisation
  • Opsonization
  • Initiation of complement

Primary goal is to prevent microbial activity and aid removal of threat from host

23
Q

Describe opsonisation

A

Refers to coating of pathogens by antibodies or complement proteins
- phagocytosis
- antibody dependent cellular cytotoxicity (ADCC)
- mast cell degranulation

24
Q

Describe complement initiation

A

Classical pathway - antibody attached to microbe

25
Q

Describe B cell activation

A
  • antigens require T cell help are called thymus-independent antigens
  • occurs in lymph nodes
  • activation of naive B cells results in the rise of plasma cells
  • plasma cells are antibody factories
26
Q

Describe B cell activation (T cell dependent)

A

T cell and BCR interactions requires co receptor binding (CD40 to CD40L)
- cytokine signals are released from T helper cell induce proliferation
- generates a pool of plasma cells which produce antibody
- also generates memory B cells
- plasma cells initially produce IgM before undergoing class switching

27
Q

What is the first antigen produced after B cell activation and how many binging sites does it have

A

IgM and 10 binding sites

28
Q

Why does class switching take place

A

Activation leads to class switching due to lgM response being weak therefore they class switch to IgG (or IgA/IgE)

This increases affinity for the antibody

29
Q

What does avidity mean

A

Ability of antibodies to form complexes

Gives a measure of the overall strength of an antigen-antibody complex

30
Q

In lymphoid organs cross talk between B and T cells leads to

A
  • humoral immunity
  • cellular immunity
31
Q

What are germinal centres

A

Hubs for T cells and B cells to cross talk and
- proliferate and differentiate
- somatic hypermutation (class switching)

32
Q

Describe vaccinations

A

B cells and T cells play a role in the process of vaccinations against a weak antigen, this leads to immunological memory, in the primary immune response IgM acts early but as B cells undergo class switching an IgG response follows

Presence of memory T and B cells means that upon second exposure the immune system can respond much faster

33
Q

What is immunological tolerance

A

Sometimes the immune system can become dysfunctional and in a state of immune unresponsiveness to a particular antigen or set of antigens, two types central and peripheral

34
Q

Describe Central tolerance

A

Can cause autoimmune disease something goes wrong in the selection of B and T cells

35
Q

Describe peripheral tolerance of T cells

A

Not all self reactive T cells are eliminated however peripheral tolerance prevents their activation

Signal 1 but no signal 2 results in anergy
Signals 1 and 2 but no 3 (cytokine survival signal) results in deletion by apoptosis
T regulatory cells can also directly block activity by binding antigen (both self and foreign antigens)

36
Q

Describe peripheral tolerance of B cells

A
  • occurs in secondary lymphoid organs
  • self reactive B cells still require help from self reactive T cells
  • since most self reactive B cells do not receive any T cell help and therefore become anergic
37
Q

Describe the term breach of tolerance

A

Breach of tolerance to self antigens or commensal organisms drives many autoimmune diseases

BAMS (41 decks)

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