lymphocyte differentiation

of 35 /35
Lymphocyte Differentiation

Upload: devona

Post on 12-Jan-2016

106 views

Category:

Documents


0 download

Embed Size (px)

DESCRIPTION

Lymphocyte Differentiation. B cell development 、 activation and maturation. Genetic Models. Genetic models: Germ-Line model The genome contributed by the grem cells contains a large repertoire of immunoglobulin genes. No special genetic mechanisms to account for antibody diversity - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Lymphocyte Differentiation

Lymphocyte Differentiation

Page 2: Lymphocyte Differentiation

Genetic Models• Genetic models:

– Germ-Line model• The genome contributed by the grem cells contains a large rep

ertoire of immunoglobulin genes.• No special genetic mechanisms to account for antibody diversi

ty– Somatic-Variation model

• The genome contains a small number of immunoglobulin genes, from which a large number of antibody specificities are generated in somatic cells by mutation or recombination.

– Two-Gene model, 1965 by W. Dryer and J. Bennett• Two separate genes encode a single immunoglobulin heavy an

d light chain, one gene for the V region and the other for the C region

B cell development、 activation and maturation

Page 3: Lymphocyte Differentiation

Verification of the two-gene model

1967, by S. Tonegawa and N. Hozumi1987, Tonegawa got Nobel Prize

(a) Digested DNA fragemnts from embryonic and myeloma cells hybridized with radiolabel-RNA

(b) V and C gene are brought closer together and intervening DNA sequence is eliminated

B cell development、 activation and maturation

Page 4: Lymphocyte Differentiation

Immunoglobulin Gene

– 總共有 7 組基因片段 (gene segments) 進行重組後表現出免疫球蛋白。

• 重鏈:– V 、 D 、 J 、 C 等 4 組基因片段。– 位於第 14 條染色體。– 具多段 VH 、多段 DH 、 6 段 JH 、 9 種 CH ( Cμ 、 Cδ 、 Cγ3 、 Cγ1 、 Cα

1 、 Cγ2 、 Cγ4 、 Cε 、 Cα2 )。

• 輕鏈( κ 及 λtype light chains ):– V 、 J 、 C 等 3 組基因片段。– κtype (多段 Vκ 、 5 段 Jκ 及單一段 Cκ 組成)位於第 2 條染色

體。– λtype (多段 Vλ 、多段 Jλ 及多段 Cλ 組成)位於第 22 條染色體。

B cell development、 activation and maturation

Page 5: Lymphocyte Differentiation

Heavy Chain DNA

κChain DNA

λ Chain DNA

Immunoglobulin Germline Gene Segments in Human

B cell development、 activation and maturation

Page 6: Lymphocyte Differentiation

Immunoglobulin Germline Gene Segments in Mouse

B cell development、 activation and maturation

Page 7: Lymphocyte Differentiation

Heavy-Chain Gene Rearrangement in HumanV-D-J joining

B cell development、 activation and maturation

Page 8: Lymphocyte Differentiation

κ- Light-Chain Gene Rearrangement in Human V-J joining

B cell development、 activation and maturation

Page 9: Lymphocyte Differentiation

λ- Light-Chain Gene Rearrangement in Human V-J joining

B cell development、 activation and maturation

Page 10: Lymphocyte Differentiation

Heavy-Chain Gene Rearrangement in the mouse V-D-J joining

B cell development、 activation and maturation

Page 11: Lymphocyte Differentiation

Kappa Light-Chain Gene Rearrangement in mouse V-J joining

B cell development、 activation and maturation

Page 12: Lymphocyte Differentiation

B cell development、 activation and maturation

Page 13: Lymphocyte Differentiation

B cell development、 activation and maturation

Overview

1. Antigen-independent phase• Immunocompetent B cells

expressing membrane IgM and IgD are generated in the bone marrow

2. Antigen-dependent phase• B cells are activated and pr

oliferated with secondary lymphoid organs

• To differentiate into memory B cell and plasma cells

Page 14: Lymphocyte Differentiation

Differentiation of B cellB cell development、 activation and maturation

Page 15: Lymphocyte Differentiation

Differentiation of B cell– pro-B cell :重排 heavy-chain genes ( DH/ JH joining ),沒有免

疫球蛋白產物。– pre-B cell :重排 heavy-chain genes ( VH /DH/ JH joining ),將 V

DJ 片段與 Cμ 連結,做出 μpolypeptide ; light-chain genes 尚未重排。

– late pre-B cell :細胞表面具有完整的 heavy chain 、 Ig-α 、 Ig-β及 surrogate light chain

– immature B cell :細胞表面具有完整的 surface IgM ( s IgM ),此時細胞可以辨識抗原,與抗原結合後造成細胞部活化及消滅,無法再進入分化過程。

B cell development、 activation and maturation

Page 16: Lymphocyte Differentiation

– mature B cell :細胞表面具 surface IgM 、 IgD (可對特殊抗體產生免疫反應)及其他表面分子,如:• 5’ nucleotidase ( CD73 ):鑲嵌於細胞膜的酵素。• CD23 :多醣蛋白( oligosaccharide-bing portein )。• adhesion proteins : LFA-1 、 ICAM-1 、 CD22 。• L-selectin : surface homing receptor ,引導細胞回到林巴結或到其他

上皮細胞。• MHC class II :呈獻抗原始 T 細胞認識。• CD40 :接受 T 細胞協助。

– 成熟 B 細胞未受刺激活化的細胞形態稱之為 virgin B cell(naïve B cell) 。– 上述之 B 細胞發育在骨髓中進行,並無特殊抗原誘發屬於 antigen-in

dependent 。當 mature B cell 進入 secondary lymphoid organs 後,因為抗原的誘導引其分化成為 plasma cell 而分泌游離之抗體( IgM )。

B cell development、 activation and maturation

Differentiation of B cell

Page 17: Lymphocyte Differentiation

B cell development、 activation and maturation

Page 18: Lymphocyte Differentiation

ac

1. Pro B-cells contact with stromal cells in the bone marrow

2. c-kit on pro B-cell interacts with stem-cell factor on surface of stromal cells

3. Pro B-cells begin to divide and differentiate into pre B-Cell

4. To express the receptor of IL-7 on the surface of pre B-Cell

B cell development、 activation and maturation

Page 19: Lymphocyte Differentiation

ac

B-1 B cell

Page 20: Lymphocyte Differentiation

B cell development、 activation and maturation

The Cell Cycle of B lymphocytes

Page 21: Lymphocyte Differentiation

B cell activation and maturation

• B 細胞活化主要因素:– Ig-α 及 Ig-β :

• 連結 B 細胞表面抗體及細胞質內之 protein tyrosine kinases ( PTKs , CD45 之細胞質內部 domain 具有此活性)。

– 抗原:• Thymus-dependent : B 細胞

與抗原(大部分之蛋白抗原)作用後,需受到 T 細胞的協助方可活化者;即 B 細胞表面分子 CD40 可與 TH 細胞表面分子 CD40L( CD40 ligand )結合後啟動。

B cell development、 activation and maturation

Page 22: Lymphocyte Differentiation

• Thymus-independen : B 細胞與抗原作用後,可自行分化產生抗體,不需受到 T 細胞的協助方可活化者;即 B 細胞可利用表面之 IgM 及 IgD 與抗原接觸後啟動 B 細胞增殖。

– T 細胞刺激:• B 細胞作為抗原呈獻細胞與 TH 細胞作用後, T 細胞會釋

放出 helper factors 活化 B 細胞。• 被活化之 B 細胞表現出 B7 proteins ( T cell costimulat

ors )並釋放出細胞激素( IL-6 、 TNFα )增加 TH 細胞活化作用的有效性。

B 細胞受到 T 細胞細胞激素作用或與 T 細胞接觸活化後,會以不同的路徑進行分化,分泌具專一性抗體。其中抗體 isotype ( class ) switching 會開始進行,轉形成 IgG 、 IgA 或 IgE 。

B cell development、 activation and maturation

B cell activation and maturation

Page 23: Lymphocyte Differentiation

• Ig-α 及 Ig-β – Immunoreceptor tyrosine-based activation motif (ITAM)

• The cytoplasmic tail of both Ig-α(61 amino acids ) and Ig-βlong (48 amino acids), 18-residue motif

• To transduce the antigen-mIg binding stimulus into cell to become an effective intracellular signal

• Binding stimulus is mediated by tyrosine kinases (PTKs)• The BCR itself has no PTK activity

• Modification of coreceptors – B-cell coreceptor:

• To provide stimulatory modifying signals• Complex of CD19, CR2 (CD21) and TAPA-1 (CD18)

– CD22• Associated with the B-cell receptor in resting B cells• A negative signal to make B-cell more difficult to activate

B cell development、 activation and maturation

Page 24: Lymphocyte Differentiation

B cell development、 activation and maturation

The initial stage of signal transduction by an activated BCR

Page 25: Lymphocyte Differentiation

• CD19: immunoglobulin superfamily protein, long cytoplasma tail, and three extracellular Ig-fold domain

• CR2: receptor of complement (C3d)

• TATP-1: transmembrane protein

B cell development、 activation and maturation

Page 26: Lymphocyte Differentiation

B cell development、 activation and maturation

• Thymus-dependent antigens (TD antigens)– Require to interact with TH cell

• Thymus-independent antigens (TI antigens)– Not to require to interact with TH cell– Typ1, such as lipopolysaccharide of bacterial cell wall

• Polyclonal B-cell activators• Activate immature and mature B cells• Fully T-cell independence

– Type2, highly repetitious molecules, such as polymeric proteins

• Not polyclonal B-cell activators• Activate mature B cells• need T-cell cytokines

Page 27: Lymphocyte Differentiation

B cell development、 activation and maturation

Signals from TI and TD Antigens for B-cell Activation

Page 28: Lymphocyte Differentiation

B-cell Activation by TD antigens

Page 29: Lymphocyte Differentiation

The Humoral Responses

- Primary and Secondary Response

Page 30: Lymphocyte Differentiation

• isotype ( class ) switching (同種形轉換):– 在 B 細胞成熟(該時期遇抗原即發生)及增殖時發生。– 利用 heavy chain gene rearrangment 來改變免疫

球蛋白的類型(此時對於已經完成之 VDJ joining 比較不會受影響,即會表現出具有相同 V 區的基因,但此情形會因體細胞基因突變而增加抗體的多樣性)。

– T 細胞及其分泌之激素對引發類別轉換具有重要的功能;如 T 細胞會傾向刺激 IgA 的形成, IL-4 刺激 B細胞產生 IgG 等。

Class Switching

Page 31: Lymphocyte Differentiation
Page 32: Lymphocyte Differentiation
Page 33: Lymphocyte Differentiation
Page 34: Lymphocyte Differentiation

Plasma cell and Memory B cell• Plasma cell :

– Plasma cells 會移入 bone marrow 中,因此 marrow 為人體 plasma cell聚集最主要的場所也是循環免抗體的主要來源。

– Plasma cells 無法複製增生,生活期也只有幾天的時間。– 細胞核具有鐘面。

• Memory B cell (記憶細胞):– 因受抗原活化而產生,且記憶形成後會表現 isotype 抗體在其細胞

表面上,具有循環特性,具有可引導淋巴細胞及組之間 homing(自動引導)作用的表面分子。

– 分佈於各淋巴組織的發生中心,此處 B 細胞抗體可變區基因的變化率很大,選擇性也很高(過程中會使細胞進行自殺作用)。

– 多種記憶性 B 細胞會聚集於初級淋巴組織中,當受抗原感染時,具專一性之記憶性 B 細胞變成 B 細胞母細胞,進行快速增殖及分化。

Page 35: Lymphocyte Differentiation