Lecture 11 - Lymphocytes Flashcards by Leah Schmid

Lymphocytes are central to

adaptive immune system and body defenses

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Three major types of lymphocytes

B cells
T cells
NL cells

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B cells

responsible for antibody production

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T cells

regulate adaptive immunity and are responsible for cell-mediated immune response

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NK cells

play a role in innate immunity

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Lymphocyte cell shape

small round cells

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Lymphocytes nucleus

large, round, stains intensely with hematoxylin

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What lymphocytes are bigger

NK larger than T or B cells

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NK cells may contain obvious

cytoplasmic granules

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Development of B vs T cells

B cells: Bone marrow, bursa, Peyer’s patches
T cells: thymus

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Distribution of B vs T cells

B cells: lymph node cortex, splenic follicles
T cells: lymph node paracortex, splenic periarteriolar sheath

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Antigen receptors of B vs T cells

B cells: BCR- immunoglobulin
T cells: TCR- protein heterodimer associated with CD3, CD4, CD8

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Important surface antigens of B vs T cells

B cells: immunoglobulin
T cells: CD2, CD3, CD4, CD8

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Antigens recognized of B vs T cells

B cells: free foreign proteins
T cells: processed foreign proeins in MHC

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Progeny cells of B vs T cells

B cells: plasma cells, memory cells
T cells: effector T cells, memory T cells

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Secreted products of B vs T cells

B cells: immunoglobulins
T cells: cytokines

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Stages in life history of lymphocytes

Naive cell->antigen recgonition->activated or effector lymphocyte->proliferation->differentiation->memory lymphocyte

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4 key antigen receptors of immune system

TCR, MHC I, MHC II, BCR

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T cell antigen receptor categories

a/B or y/g

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a/B T cell accessory molecules

CD4 and CD8

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CD4 functional subdivision

Helper/Regulatory and memory

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CD8 functional subdivisions

cytotoxic/regulatory and memory

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T cell antigen receptors

aB and yg

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T cell surface receptors

CD4 and CD8

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aB T cells

1. CD4+ aB T cells 2. CD8+ aB T cells

T helper cells or CD4+ aB T cells recognize

antigen on MHC II

type of T helper cell is defined by

cytokines secreted not by surface molecule

Naive TH cells are called

TH0 cells

TH0 cells differentiate into

TH1, TH2, TH17, Treg

TH0 cell differentiation depends on

signals TH0 cells receive from APCs and the local environment

TH1 cells secrete

IFNy, IL-2

TH1 cells are important in protection against

some intracellular (viral, Mycobaterium, Salmonella, Listeria, Brucella) and extracellular pathogens

TH1 cells secrete cytokines that activate

macrophages, meutrophils, NK cells, and CTLs to be better killers

TH1 cells secrete cytokines that signal

B cells to make opsonizing and complement fixing antibodies for extracellular bacteria or certain viruses

TH2 cells secrete

IL-4, IL-5, IL-9, IL-13

TH2 activate

mast cells and eosinophils, and B cells to make IgE

TH2 cells provide defense against

some parasites and some mucosal pathogens

TH2cells are important in

IgE mediated allergies

TH17 cells secrete

IL-17, IL-21, IL-22

Th17 attract and activate

neutrophils and monocyte, leading to acute inflammation

TH17 cells important in

response to extracellular bacteria and fungi

Treg cells secrete

IL-10, IL-35, TGFB

Treg supress

T cell response by secreting suppresive cytokines

Treg help prevent

reactions to self-peptides

If naive T cell recognizes antigen without any danger signals, it may become

Treg

In most cases a self antigen would be encountered in the absence of ______. These self-reactive T cells are then induced to become _____ and do not induce an immune response to the self-antigen but ____

inflammation; Treg, prevent it

Another name for cytotoxic T lymphocytes

CTLs/CD8 T cells

CD* aB t cells recognize antigen on

MHC I

What do CD8+ aB T cells do once they encounter antigen

clonally expand, differentiate and develop a killing machinery in their cytoplasm, kill cell that has antigen it recognizes bound to an MHC I molecule

CD8+ aB T cells

important in protection from intracellular microbes that cause the synthesis of foreign proteins in the cytoplasm, such as viruses

yG T cells defined by their

TCR

yG T cells recognize

intact, unprocessed antigens; also recognize cell surface 'stress' proteins, (recognize protein and non-protein antigens)

yG T cells important at

mucosal surfaces, many are intraepithelial lymphocytes

yG T cells are not as well understood as

aB T cells

B cells antigen recognition

intact, unprocessed molecules

B cells response to antigen

plasma cells produce antibodies

CD4+ TH1 antigen recognition

Exogenous peptides, processed and presented in MHC II

CD4+ TH2 antigen recognition

exogenous peptides, processed and presented on MHC II

CD4+ Treg antigen recognition

self-peptides on MHC II

CD8+ T cytotoxic cells (CTL) antigen recognition

endogenous peptides, processed and presented on MHC I

yG T cells antigen recognition

intact, unprocessed antigens, also 'stress proteins'

CD4+ TH1 response to antigen

Secrete cytokines which activate phagocytes, NK, CTLs to fight intravesicular pathogens, influence B cells to make antibody for extracellular pathogens

CD4+ TH2 response to antigen

Secrete cytokines which help antibody production, especially IgE, to fight parasites and cause allergies

CD4+ TH17 response to antigen

Secrete cytokines that stimulate production of neutrophil chemokines by cells at the site of infection

CD4+ T reg response to antigen

Secrete suppressive cytokines or suppress T cell responses by cell-cell contact

CD8+ T cytotoxic cells (CTL) response to antigen

Cytotoxic for cell synthesizing foreign proteins

yG T cells response to antigen

Secrete cytokines and/or cytotoxic for cells with abnormal surface antigens, stress markers, heat shock proteins

NK cells are NOT ___ and have NO ____

1. antigen specific 2. surface immunoglobulin (CD3, CD4, CD8)

NK cells activated by

IFNy, TNF, IL-2

NK cells cytotoxic for cells that

do not express normal MHC I molecules with normal peptides, or cells that express stress proteins

3 major receptors of NK cells

1. Ly49 2. NKG2D 3. CD16

Lymphocytes all look the same byt can be differentiated by

characterisitic cell surface molecules

cell surface molecules are classified by the

CD (cluster of differentiation) system