El linfocito B

El linfocito B: lo fundamentalInmunología Básica

Mayo 2011

Persio D. López

1Sunday, May 22, 2011

¿Qué veremos hoy?Abbas AK, Lichtman AH. Cellular and molecular immunology. Philadelphia, PA: Saunders; 2005:564.

Figure 1.1; p. 5.2Sunday, May 22, 2011

Pro-B Pre-B Immature B Transitional B Mature B

µ/ IgM IgD and IgM

IgM

IgG

IgA

IgE

IgD

VHDHJHrearrangement

CSR

IgM plasma cell

IgG plasma cell

IgA plasma cell

IgE plasma cell

IgD plasma cell

VLJLrearrangement Antigen

stimulation

Bone marrow Periphery

Transcription

Transcription

Transcription

Transcription

Splicing

Splicing

Splicing

Splicing

TransmembraneIgM

Secreted IgD

TransmembraneIgD

Secreted IgM

L V D J Iµ Sµ Cµ1 Cµ3 µm1 µ C 1 H1 C 2 S m1

Poly-An Poly-An Poly-An Poly-An

Human genomic IgM-IgD region

Cµ2 Cµ4 µm2 H2 C 3 m2

+

+





IgD IgM DAPI

A C

B

D

Chen & Cerutti Æ Regulation and function of IgD

166 ! 2010 John Wiley & Sons A/S • Immunological Reviews 237/2010

¿Qué veremos hoy?Chen K, Cerutti A. New insights into the enigma of immunoglobulin D. Immunol Rev. 2010;237:160-179.

Figure 2a, Expression of human IgD by alternative splicing and CSR; p. 167.2Sunday, May 22, 2011

µ

Chromosome 14n = ~50

Germline DNADJ rearrangement Deletion

VDJ-rearrangement

Transcription

DJ-Cµ mRNA DJ-Cµ protein

Cleavageof L-codedsequence

VDJ-Cµ coding mRNA µ heavychainsA. Organization and rearrangement of immunoglobulin H genes

B. Organization of ! light chain genes

C. Organization of " light chain genes

3'5'

3'

C#4

5'

Deletion

5' 3'

VH1 VH2

D. Immunoglobulin class-switching

V D Js s s Maturation

mRNA

lgM-expressing B cell lgG1 -expressing B cell

V D J

mRNA

s

#1

s

Chromosome 223'

V"1 V"x

5'

V"n

Chromosome 2

n = ~35

3'

V$1 V$2 V$n

5'

V$3

✂✂

VH1 VH2 VnVH3

L1 L2 L3 Ln D1 D2 D3 D4 Dn J2J1 J3 J4 J5 J6 CµC% C#3 C#1 C&1 C#2 C#4 C' C&2

L1 L2 L3 Ln D1D2D3 J6 CµC% C#3 C#1 C&1 C#2 C' C&2J5

VH1 VH2 VnVH3

J6 Cµ C% C#3 C#1 C&1 C#2 C#4 C( C&2L1 L2 D3 J5

L1 L2 L3 Ln J$2J$1 J$3 J$4 J$5 C$

L1 Lx LnVpreB J"2 C"2 J"4 C"4 C"xJ"x

C#3 C#1Cµ C% C&1

C µ

C%

C #3

C#1

!""#$%&'%(#')$ *+$+ ,-&.$)/.0)%$!

"

!

1#$2

."+$

0.'3-

)$4)5'+6

78

"Burmester, Color Atlas of Immunology © 2003 ThiemeAll rights reserved. Usage subject to terms and conditions of license.

Lo básicoBurmester G-R, Pezzutto A, Ulrichs T, Aicher A. Color atlas of immunology. Stuttgart ; New York: Thieme; 2003.

Figure 15, Organization and rearrangement of immunoglobulin genes; p. 31.


µ

Chromosome 14n = ~50

Germline DNADJ rearrangement Deletion

VDJ-rearrangement

Transcription

DJ-Cµ mRNA DJ-Cµ protein

Cleavageof L-codedsequence

VDJ-Cµ coding mRNA µ heavychainsA. Organization and rearrangement of immunoglobulin H genes

B. Organization of ! light chain genes

C. Organization of " light chain genes

3'5'

3'

C#4

5'

Deletion

5' 3'

VH1 VH2

D. Immunoglobulin class-switching

V D Js s s Maturation

mRNA

lgM-expressing B cell lgG1 -expressing B cell

V D J

mRNA

s

#1

s

Chromosome 223'

V"1 V"x

5'

V"n

Chromosome 2

n = ~35

3'

V$1 V$2 V$n

5'

V$3

✂✂

VH1 VH2 VnVH3

L1 L2 L3 Ln D1 D2 D3 D4 Dn J2J1 J3 J4 J5 J6 CµC% C#3 C#1 C&1 C#2 C#4 C' C&2

L1 L2 L3 Ln D1D2D3 J6 CµC% C#3 C#1 C&1 C#2 C' C&2J5

VH1 VH2 VnVH3

J6 Cµ C% C#3 C#1 C&1 C#2 C#4 C( C&2L1 L2 D3 J5

L1 L2 L3 Ln J$2J$1 J$3 J$4 J$5 C$

L1 Lx LnVpreB J"2 C"2 J"4 C"4 C"xJ"x

C#3 C#1Cµ C% C&1C µ

C%

C #3

C#1

!""#$%&'%(#')$ *+$+ ,-&.$)/.0)%$!

"

!1#

$2."

+$0.'3-

)$4)5'+6

78


Lo básicoBurmester G-R, Pezzutto A, Ulrichs T, Aicher A. Color atlas of immunology. Stuttgart ; New York: Thieme; 2003.

Figure 15, Organization and rearrangement of immunoglobulin genes; p. 31.


A. B-cell differentiation scheme

pro-B pre-B-I pre-B-II Immature B Mature B Plasma cellHL A -class I I

(HL A -DR)CD34

CD10

lg-!/lg-"

Cytoplasmic

Surface

VpreB/#5

Immunoglobulinscyt-µ slgM/slgD

CD22

CD19

CD20

CD21

CD23

Surface

IL-7RCD34 CD19

CD22cyt

DJ-rearrangement

VpreB/#5Pro-B

transcriptionDJ-Cµ

pre-B-I

IL-7RCD19

L$H

L#

L$H

L#

B. Immunoglobulin modulation during B-cell differentiation

CD10

Prot.

CD19

DJ-Cµ

L$H

L#

VL-JL-

Pre-B-II

VDJ-rearrangement

Rearrangement

Hµ/VpreB/#5

CD10

CD19

L$H

L#

CD22s

CD20

CD21CD23Mature B

slgM+

or

HµL$

HµL#

CD19

Immature B

Hµ/L$ (slgM)

CD20

CD19CD22cyt

or

Hµ/L#(slgM)

VpreB/#5

VpreB/#5

Hµ/VpreB/#5

Pre-B-I

CD22cyt

CD22cyt

CD22cyt

(slgM)

CD10

!""#$%&'%(#')$ *+$+ ,-%.#/0 123-+44)%$!

"

!

5#$.

6"+$

06',-

)$/)3'+4

77


Burmester G-R, Pezzutto A, Ulrichs T, Aicher A. Color atlas of immunology. Stuttgart ; New York:

Thieme; 2003. Figure 16b, Immunoglobulin modulation during B-cell differentiation; p. 33.

El comienzo


El comienzoShapiro-Shelef M, Calame K. Regulation of plasma-cell development. Nature Reviews Immunology.

2005;5:230-242. Figure 1, Antigen-independent development of B cells; p. 231.

Bone marrow

HSC Pro-B cell Pre-B cell

Pre-BCRIgM+

IgD–

Naive B cell(immature)

Spleen

Naive long-livedfollicular B cell

Naive marginal-zone B cell

IgMlow

IgDhi

CD21int

CD23+

IgMhi

IgDhi

CD21hi

CD23+

IgMhi

IgDlow

CD21hi

CD23–

T1 B cellT2 B cell

IgMhi

IgDlow

CD21low

CD23–


El comienzo


µ/ IgM IgD and IgM

IgM

IgG

IgA

IgE

IgD

VHDHJHrearrangement

CSR

IgM plasma cell

IgG plasma cell

IgA plasma cell

IgE plasma cell

IgD plasma cell


stimulation


Transcription

Transcription

Transcription

Transcription

Splicing

Splicing

Splicing

Splicing

TransmembraneIgM

Secreted IgD

TransmembraneIgD

Secreted IgM





+

+





IgD IgM DAPI

A C

B

D



Chen K, Cerutti A. New insights into the enigma of immunoglobulin D. Immunol Rev. 2010;237:160-179. Figure 2d, Expression of human IgD by alternative splicing and CSR; p. 166.


La regulaciónPaul WE. Fundamental Immunology. 6th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2008.

Figure 7.4, Transcription factors important at different stages in B cell development in mouse bone marrow.


Paul WE. Fundamental Immunology. 6th ed. Philadelphia: Wolters Kluwer/Lippincott Williams &

Wilkins; 2008. Figure 1.4, Two forms of B cell activation; p. 7.

La activación


La activación

Abbas AK, Lichtman AH. Cellular and molecular immunology. Philadelphia, PA: Saunders; 2005:564.

Figure 9.3; p. 192.


La activaciónAbbas AK, Lichtman AH. Cellular and molecular immunology. Philadelphia, PA:

Saunders; 2005:564. Figure 9.4; p. 194.8Sunday, May 22, 2011

La producción

Shapiro-Shelef M, Calame K. Regulation of plasma-cell development. Nature Reviews Immunology.

2005;5:230-242. Figure 2, Formation of plasma cells; p. 232.

©!!""#!Nature Publishing Group!

!

R E V I EW S

232 | MARCH 2005 | VOLUME 5 www.nature.com/reviews/immunol

BCRs and express switched immunoglobulin isotypes,exit the germinal centre.

Memory-cell response. Post-germinal-centre memory B cells retain high-affinity BCR at their cell surface, donot secrete antibody and (at least one subset) can persistindependently of antigenic stimulation when gene tar-geting is used to change the specificity of the BCR20,21.Memory B cells have the intrinsic ability to respondmore rapidly than naive B cells, and they show a prolif-erative burst on secondary encounter with antigen22.Complement receptors expressed by stromal cells arerequired for this rapid recall response19. Stimulation ofhuman memory B cells ex vivo shows that bystander T-cell signals and CPG-CONTAINING OLIGODEOXYNUCLEOTIDES

can suffice to stimulate the differentiation of memory B cells, indicating a way to replenish and/or maintainmemory and plasma cells in the absence of furtherexposure to antigen23.

A unique subset of BCR+CD79b+B220–syndecan 1(SDC1)– cells in the bone marrow was shown by adop-tive transfer to be ‘pre-plasma’ memory cells; these cellsdifferentiate into plasma cells on secondary encounterwith antigen more readily than do the B220+ memorysubset in the spleen24. However, this pre-plasma memory-cell subset is controversial because another researchgroup has suggested that they are non-B cells that cap-ture BCRs using cell-surface Fc receptors25. BCR+B220low

SDC1+CD44+ bone-marrow cells that differentiate intoplasma cells independent of antigen have also beendescribed26. The relationship between these two bone-marrow cell populations is unresolved at present. Thecommon requirement for B-lymphocyte-induced mat-uration protein 1 (BLIMP1) in the formation of plasmacells and pre-plasma memory cells led us to speculatethat post-germinal-centre cells might develop through a single pathway that leads from memory B cells toplasma cells27. The alternative possibility is that memoryB cells and plasma cells are two separate fates of the B cellsthat leave the germinal centre.

Relationships between cell division and plasma-cell differentiation. Before differentiation into plasma cells,activated B cells undergo a strong proliferative burst.Studies using a division-tracking dye to assess cell divi-sions of B cells stimulated in vitro showed that, at eachcell division, there was a probability of commitment tothe plasmacytic fate, and this probability was increased inthe presence of interleukin-4 (IL-4) or IL-5 (REFS 28,29).Clearly, the clonal expansion of cells that are committedto a plasma-cell fate amplifies the selected antibodyresponse, but these studies indicate that proliferationmight be a mechanistic requirement for plasmacytic dif-ferentiation. Because replication provides an opportu-nity for epigenetic remodelling, it will be interesting tostudy unactivated B cells and examine the chromatinstructures of the genes that are crucial for plasma cells.Ultimately, proliferation ceases and non-dividing plasmacells are formed, but it is interesting that BLIMP1expression and immunoglobulin secretion precede thecessation of the cell cycle.

in the follicle where B cells undergo rounds of prolifera-tion, which is accompanied by affinity maturation andCLASS-SWITCH RECOMBINATION (CSR) of immunoglobulin.Antigen-specific T helper cells and FOLLICULAR DENDRITIC

CELLS (FDCs) are important for the germinal-centreresponse15. Interactions between CD40 ligand (CD40L)–CD40 and inducible T-cell co-stimulator (ICOS)–ICOSligand — which are present at the cell surface of T and B cells, respectively — are important, as are cytokinesexpressed by T cells16. T helper cells present in the germi-nal centre have unique properties, including high-levelexpression of CXC-chemokine ligand 13 (CXCL13)17

and the adaptor protein SAP (signalling lymphocyte-activation molecule (SLAM)-associated protein), whichis required for providing help18. FDCs sequester antigenin the germinal centre, and complement receptors(CD21 and CD35) expressed by FDCs are crucial forthis function19. The germinal-centre response peaksbetween day 10 and day 14 after immunization andthen diminishes. Plasma cells and memory B cells,which mainly have somatically mutated, high-affinity

CLASS-SWITCH

RECOMBINATION

(CSR). A DNA rearrangement in which deletion replaces oneimmunoglobulin heavy-chainconstant-region gene segment(usually µ) with a more 3! genesegment (", # or $).

FOLLICULAR DENDRITIC CELLS

(FDCs). Specialized cells ofunknown origin, which holdantigen–antibody complexes ingerminal centres and are crucialfor optimal selection of B cellsthat produce antigen-bindingantibody.

CPG-CONTAINING

OLIGODEOXYNUCLEOTIDES

DNA oligonucleotides thatcontain unmethylated CpGbases, which are commonlyfound in bacteria.

Apoptotic cell

Selectionand CSR

ASC

Plasmacell

Plasmacell

Plasmacell

Naturalantibodiesand IgA

MemoryB cell

Survivalin bonemarrow

Germinal centre

Proliferationand mutation

Week 1 Week 2 Week 3

IgM

IgG, IgAor IgE

B1 cell

Marginal-zoneB cell

FollicularB cell

IgM

Figure 2 | Formation of plasma cells. Antibody-secreting cells (ASCs) formed from B1 cellssecrete natural antibody in the absence of external antigen, and they also secrete IgA in the gut,in response to pathogens. On encounter with foreign antigen (indicated by week 1 in figure), naivemarginal-zone B cells differentiate into plasma cells, and subsequently, naive follicular B cells alsodifferentiate into plasma cells. Most of the extrafollicular plasma cells that are formed in this earlyresponse are short-lived. Some activated follicular B cells form a germinal centre. Post-germinal-centre plasma cells might progress through a memory B-cell stage in the primary response ormight develop directly from germinal-centre B cells (for further details, see main text). Plasma cellsthat result from a germinal-centre reaction might become long-lived if they find survival niches,which are mainly located in the bone marrow. CSR, class-switch recombination.


La producción

Paul WE. Fundamental Immunology. 6th ed. Philadelphia: Wolters Kluwer/Lippincott Williams &

Wilkins; 2008. Figure 9.6, The GC pathway to memory B cell development.


La producción

ANRV313-BI76-01 ARI 23 May 2007 22:20

C

U

Rev1

Xrcc2Xrcc3

ReplicativeDNA Pol?

MSH2/6ExoIPol!

Other TLS polymerases

(Pol"?)

NHEJ

G

GTA

TA

AT

G

GC

IgV geneconversion

Class switchrecombination

Transitionsat C:G pairs

Transversions + transitionsat C:G pairs

Mutationsat A:T pairs

AID

UNG

Figure 2DNA deamination model of immunoglobulin gene diversification, emphasizing somatic hypermutationand indicating some of the key enzymes implicated in each pathway. Abbreviations: AID,activation-induced deaminase; ExoI, mismatch repair exonuclease I; IgV, immunoglobulin variableregion; NHEJ, nonhomolgous end joining; MSH2/6, mismatch recognition proteins; Pol, polymerase;Rev1, Y-family DNA polymerase involved in DNA damage tolerance; TLS, translesion synthesis; UNG,uracil-DNA glycosylase; Xrcc2 and Xrcc2, Rad51 paralog proteins involved in homologousrecombination repair.

diversification pathways: Modifying or ablat-ing enzymes involved in processing U:G le-sions should therefore significantly perturbantibody gene diversification pathways. Bothtypes of prediction have been confirmed in avariety of studies.

Thus, both bacterial genetic studies as wellas biochemical studies of recombinant AIDhave confirmed that it is able to deaminatecytosine in DNA (47, 54–59). Indeed, AIDshows a preference for C residues that liewithin a WRC consensus, suggesting that

the WRCY hot spots observed during IgVsomatic mutation in vivo could result fromAID oligomers acting preferentially on tar-gets comprising overlapping WRC motifs onopposite DNA strands (57, 60).

With regard to genetic evidence thatthe U:G lesion is an intermediate in anti-body diversification, a deficiency in the majoruracil-excision enzyme (UNG) perturbs so-matic mutation, gene conversion, and switchrecombination exactly as predicted by thescheme (61–66). Similarly, the second phase

8 Di Noia · Neuberger

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Di Noia JM, Neuberger MS. Molecular mechanisms of antibody somatic hypermutation. Annu Rev Biochem. 2007;76:1-22. Figure 2, DNA deamination model of

immunoglobulin gene diversification; p. 8.


A fin de cuentas…Chen K, Cerutti A. New insights into the enigma of immunoglobulin D. Immunol Rev. 2010;237:160-179.

Figure 2a, Expression of human IgD by alternative splicing and CSR; p. 167.


µ/ IgM IgD and IgM

IgM

IgG

IgA

IgE

IgD

VHDHJHrearrangement

CSR

IgM plasma cell

IgG plasma cell

IgA plasma cell

IgE plasma cell

IgD plasma cell


stimulation


Transcription

Transcription

Transcription

Transcription

Splicing

Splicing

Splicing

Splicing

TransmembraneIgM

Secreted IgD

TransmembraneIgD

Secreted IgM





+

+





IgD IgM DAPI

A C

B

D




A fin de cuentas…

Albumin Globulins

!1 !2 "

A. Protein electrophoresis

1. Circulating Ig

B. Different immunoglobulin types

2. Membrane-2. bound Ig

Breastmilk

Fcreceptors

3. Secretory Ig 4. Cell-bound IgIgGIgAIgM IgD

IgE

65%IgG1

23%IgG2

8%IgG3

4%IgG4

SecretorylgA; dimer

V

VLSerum:Monomeric lgA

Serum: lgM

Membrane-bound lgM

MatureB lymphocyte

Serum: lgD

Membrane-bound lgD

Basophilgranulocyte

Serum lg 80% 13% 6% 0.1% 0.002%

Half-life 23 6 5 3 2.5 days

C. Immunglobulin structure and features

Fc#R Binding at pH <7.0

J chainlgApH 7.4 Release at pH 7.4

Lumen

D. IgG transport through intestinal epithelium E. Secretion of IgA

SS

SS

SS

SS

SS

SSSSSSSS

SSSSSSSSSSSSSSSSSSSSSS

S S

SS

#

IgG IgA IgM IgD

SS

SS

SS

SS

SS

S SS S

SS

MatureB lymphocyte

CL

SS

SS

Lumen

Jchain SS

Hingeregion

Secretory component

!""#$%&'%(#')$ *'+,,-,!

"

!.#

$/+"

-$0+'12

)$3)4'-,

56


Burmester G-R, Pezzutto A, Ulrichs T, Aicher A. Color atlas of immunology. Stuttgart ; New York: Thieme; 2003. Figure 14c, Immunoglobulin structure and features; p. 29.


1. recombinación de genes germinales

2. imprecisión en el sitio de unión de ciertos grupos de AAs (V/D, D/J)

3. expresión de TdT

4. combinación de VH con VL

5. hipermutación somática

6. flexibilidad molecular

6 fuentes de variación


Buen día.

Paul WE. Fundamental Immunology. 6th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2008.

Roitt IM, Brostoff J, Male DK. Immunology. 7th ed. Edinburgh; New York: Mosby; 2009.

Kindt TJ, Goldsby RA, Osborne BA, Kuby J. Kuby immunology. 6th ed. New York: W.H. Freeman; 2007.

Abbas AK, Lichtman AH. Cellular and molecular immunology. 5th ed. Philadelphia, PA: Saunders; 2005.


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