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Phar 504 > Lymphocyte activation: B cell > Flashcards

Lymphocyte activation: B cell Flashcards

1
Q

What are the phenotypic markers found at the surface of B cells

A

CD19,CD20,CD21, MHC 2, Surface Ab (IgD/IgM)

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2
Q

T/F: Plasma cells do not have surface Ab

A

True

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3
Q

Where are most B cells located

A

In the lymph nodes,MALT, splenic marginal zone

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4
Q

B cell receptor

A

the antigen recognition unit in the form of membrane bound antibody (Ig), usually IgM or IgD

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5
Q

What is the function of CD21,CD19

A

CD21 binds opsonized antigenic particles, CD19 is primarily responsible for signal transduction

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6
Q

What are the two ways a B cell can be activated

A

Thymus-dependent (TD) Antigen, Thymus-Independent(TI) Antigen

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7
Q

What occurs in thymus dependent antigen B cell activation

A

protein antigen that require activation are guided by the CD4+ Th cells (helper T cell required)

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8
Q

What occurs in thymus independent antigen B cell activation

A

polymeric Antigen that crosslink the BCR and directly activate the B cell

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9
Q

What are the locations that will determine thymus dependent activation

A

lymph node germinal center, MALT

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10
Q

What are the location that will determine thymus independent activation

A

Splenic marginal zone

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11
Q

What are the three signals required for naive B cell activation via thymus dependent antigen

A

Signal 1: BCR encounters Antigen, Signal 2: costimulatory signal, Signal 3: cytokine signal

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12
Q

How long does it take for a response in thymus dependent antigen activation, how specific are the antibodies

A

5-15 days, specific for more than just one epitope of a particular antigen

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13
Q

T/F: Only Thymus dependent antigen B cell activation will give rise to memory B cells

A

True

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14
Q

What happens once a B cell recognizes an antigen as a soluble protein

A

A protein will bind the B cell receptor causing it to be internalized and digested, Peptides will be joined to MHC 2 and placed on the outside

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15
Q

T/F: Without co-stimulation a helper T cell can still have activity

A

False: Without co-stimulation there will be nothing that occurs after these interactions

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16
Q

What are the ctyokines that aid a B cell in turning into a plasma cell

A

IL-4, IL-5

17
Q

What bond causes the second signal or costimulation in Thymus dependent antigen activation

A

CD40-L (CD4+) and CD40 (B cell)

18
Q

What is the other costimulatory pair besides CD40/CD40L, what is the action

A

B7/CD28, activate the T-cell

19
Q

How does CD40/CD40L affect the B cell

A

Promotes up regulation of B7 on B cell, promotes B cell proliferation (clonal expansion), Promotes somatic hypermutation (higher affinity), class switching ( diffrent typers of antibodies made), promote B cell formation

20
Q

How does CD40/CD40L affect the T cell

A

Promote T cell to secrete cytokines that will promote growth and antibody production by the activated B-cell

21
Q

What is needed for a secondary response to occur

A

The same epitopes must be presented to B and T cells

22
Q

Why is the secondary response better than the primary responce

A

higher affinity due to somatic hypermutation -> respond more rapidly -> generate more progeny -> produce higher concentrations of antibodies

23
Q

How fast is Thymus independent activation, where is it localized

A

within 2 days,marginal zone of the spleen

24
Q

T/F: Thymus independent activation causes immunologic memory

A

False: Thymus independent activation does not create immunologic memory

25
Q

What are the antibodies created in thymus independent activation, are there other antibodies created

A

IgM, no

26
Q

What are the two types of Thymus independent antigen activation

A

Type 1:Mitogens activate multiple different B cell clones to produce antibodies (polyclonal response), Type 2: multiple and repeating identical epitopes

27
Q

What are the signals that occur in Type 1 (mitogen) Thymus independent activation

A

1st signal: BCR binds polymeric Antigen (mitogen binds but NON-SPECIFICALLY) 2nd signal: Toll like recpetors respond to the mitogen

28
Q

What is the result of Type 1 (mitogen) thymus independent activation

A

Pattern recognition receptor on the B cell leads to cell division and antibody production

29
Q

What are the signals that occur in Type 2 (repeating BCR) thymus independent activation

A

1st signal: BCR binds antigen with repeating identical epitopes 2nd signal: provided by clustering of BCRs

30
Q

What are the type of antigens that cause Type 1 thymus independent activation, type 2

A

Type 1: lipopolysachrides derived from cell walls and protein coats of viruses, Type 2: bacterial flagelin, bacterial and fungal polysachrides, nucleic acids

31
Q

What is the key difference between type 1 and type 2

A

Type 1 can activate multiple B cells leading to polycloncal activation of B cells

32
Q

What are key features of Thymus independent antigen activation

A

Essention in recognition of non-protien antigens, generate primarliy low affinity IgM antibodies (no class switching and no somatic hypermutation), not developed until 2nd year of life

33
Q

What are the three key transcription factors in intracellular signalling pathway after thymus dependent activation, what are the results

A

NFAT, NFkB, AP-1, proliferation/synthesis of Ig/cytokine receptors

34
Q

What are the maturation events in thymus dependent antigen activation

A

class switching, somatic hypermutation, differentiation into antibody producing plasma cell or memory B cell

35
Q

T/F: Maturation events occur in both thymus dependent antigen activation and thymus independent antigen activation

A

False: Maturation events only occur in thymus dependent antigen activation

36
Q

What are the antibodies that cause aggultination, complement activation

A

IgG/IgM/IgA, IgG/IgM

37
Q

What are the five steps of the hummoral immunity

A

1) Inactivation of viruses and neturilizations of bacterial toxins 2) Cells clump or agglutinate 3) Ag-Ab complex formation leads to complement fixation 4) macrophages have enhanced phagocytosis due to Fc receptors 5) Destruction by non specific immune cells

38
Q

What percentage of B lymphocytes circulates

A

10-15%

Phar 504 (34 decks)

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