adaptive immunity: B cells Flashcards

1
Q

what are B cells?

A

communicate with T cells, have specific B cell receptor for antigens, produce antibodies

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2
Q

what is clonal expansion?

A

generation of 2 subsets

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3
Q

what ae plasma cells

A

large antibody factories

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4
Q

what are memory B cells?

A

mount a quicker antibody response to any subsequent infections

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5
Q

where do you find B cells?

A

mature in bone marrow, circulate in blood and lymph and are found in large numbers in lymphoid organs

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6
Q

how do B cells recognize antigens?

A

through B Cell Receptor which is actual antibody - diversity

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7
Q

what do b cells become once activated

A

plasma cells

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8
Q

what are the 5 types of immunoglobulins produces by b cells (as receptors)

A

IgG, IgE, IgD, IgM, IgA

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9
Q

describe b cell receptor structure

A

different to t cells, but has variable and constant regions, and light and heavy chains

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10
Q

what are the 3 main functions of antibodies?

A

neutralization, opsonization, initiation of complement

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11
Q

what is the goal of antibodies?

A

prevent microbial activity and aid removal of threat from host

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12
Q

what is opsonisation?

A

coating of pathogens by antibodies or complement proteins; phagocytosis, antibody dependent cellular cytotoxicity, mast cell degranulation

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13
Q

describe b cell development

A

each development stage is defines by rearrangements of the immunoglobulin heavy and light chain genes, once in periphery b cells migrate to secondary lymphoid organs

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14
Q

what are the components of heavy chain?

A

variable, diversity and joining genes

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15
Q

what are the components of light chain?

A

variable and joining genes

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16
Q

what immunoglobulins do immature and mature b cells express?

A
immature = IgM
mature = IgM and IgD
17
Q

how do b cells undergo negative selection?

A

macrophages engulf and remove self- reacting b cells

18
Q

what are the 2 types of b cell activation?

A

thymus-dependent
antigens which don’t require t cell help
thymus-independent
antigens which dont

19
Q

describe b cell activation

A

occurs n lymph nodes

activation of naïve b cell results in rise of plasma cells

20
Q

describe thymus-dependent activation

A

co-receptor binding, cytokine signals released from t helper cells induce proliferation
generates pool of plasma cells which produce antibody
also generates memory b cells
plasma cells initially produce IgM

21
Q

describe thymus-independent activation

A

certain antigens can activate directly, cells differentiate into plasma and produce IgM but antibody response weaker than antigen dependant b cell activation, doesn’t lead to generation of memory cells

22
Q

what is class switching?

A

caused by class switching, IgM response is weak, cells class switch to IgG, occurs by gene rearrangement, but antigen binding site remains same, antibody has increasing affinity for antigen

23
Q

what is avidity?

A

ability of antibodies to form complexes

24
Q

what is cross talk?

A

in lymphoid organs, between B and T cells, leads to generation of both humoral and cellular immune response

25
Q

what are germinal centres?

A

hubs for t and b cross talk, also proliferation, differentiation, somatic hypermutation-class switching

26
Q

describe the vaccination process

A

in 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 on 2nd exposure immune system responds much faster, cells also primed to produce more effective IgG response immediately

27
Q

what is immunological tolerance?

A

an active response to a particular antigen-central and peripheral

28
Q

what is central tolerance

A

in primary lymphoid organs- thymus for t and bone marrow for b, + and - selection eliminates >90% of t cells

29
Q

what is peripheral tolerance (t cells)

A

not all self reactive t cells are eliminated, however peripheral tolerance prevents their activation

30
Q

signal 1, no signal 2 =

A

anergy

31
Q

signal 1 + 2 no 3 =

A

deletion by apoptosis

32
Q

what can Treg cells do in peripheral tolerance?

A

directly block activity by binding antigen

33
Q

what is peripheral tolerance (in b cells)

A

occurs in secondary lymphoid organs, self reactive b cells still require help from self reactive t cells, since most eliminated the b cells become anergic

34
Q

what is breach of tolerance?

A

to self antigens or commensal organisms drived many autoimmune diseases