The development of lymphocytes Ch8 The development of lymphocytes

Immune system Design for living Boundary Self/non-self recognition

Ags………. Gene rearranged receptors: TCR/BCR Germline-encoded receptors Innate immunity Germline-encoded receptors Adaptive immunity Gene rearranged receptors: TCR/BCR Lymphopoiesis

B/T cell development Cells Microenvironment AgR

Adaptive immunity 1. Antigen specificity 2. Diversity 3. Immunological memory 4. Self tolerance

Aim of development Self Ag? MHC-restricted? Production of AgR 2. Functional Ag recognition Self Ag? MHC-restricted?

Hematopoiesis Central lymphoid organs Microenvironment Commitment Productive rearrangement? Cell survival & death

One cell one AgR Clone Fate

B-cell development T-cell development Positive & negative selection

B cell development Die Microenvironment Survive

Transcription factors Proteins, receptors

The dependence on bone marrow stromal cells Adhesion molecules Early stages Growth factors Cell-cell interaction B cell commitment Proliferation (SDF-1) Constitutive production

Ig gene rearrangement

One receptor on one cell Heavy chain One receptor on one cell Allelic exclusion

Protein-regulated gene rearrangement

Protein-regulated gene rearrangement

Cell survival or death

Self-reactivity Fate The presence of autoreactive lymphocytes in periphery

Receptor editing 21

7-8 Fig. 7-23 22

T B-cell development Stromal cell-dependent (Spatial regulation) B cell commitment BCR rearrangement Cell survival & death (BCR, self tolerance) Stromal cell-dependent (Spatial regulation) Temporal regulation of protein expression Proteins: receptors, cytokines, TS factors, recombinase, ..)

T cell development Self MHC restriction Self tolerance Cells Microenvironment

Affinity

Epithelial cell network: thymic stroma Thymus 26

The importance of thymus in T-cell development Thymectomy DiGeorge’s syndrome Defective repairing system Genetic defect of a gene coding for transcription factor Wnt required for terminal differentiation of cortical epithelial cells

Cells & microenvironment

Flow cytometry

T cell development gdTCR

T cell subsets in central and peripheral organs Flow cytometry: immunostaining Normal

T cell commitment R: Notch 1

Microenvironment

abTCR or gdTCR ? b

Developmental control of gd T cells Ordered sequence

abTCR or gdTCR ? b

Cells Repeated rearrangements can rescue nonproductive VaJa joins 37

a gene rearrangement induces d gene deletion

39

Microenvironment After TCR rearrangement MHC restriction Self tolerance 40

Positive selection : MHC restriction Cortex MHCI-CD8 MHCII-CD4 41

Positive selection (T cell precursor) T cells : thymus MHC restriction

Ag encounter in periphery Bone marrow-derived DC/macrophages 43

Bone marrow chimera Thymic non-lymphoid stroma Bone marrow-derived APC

Negative selection: self tolerance Bone marrow-derived 45

Negative selection : Self tolerance AIRE expression on thymic medulary cells Medulary epithelial marker MTS10 Self antigen (encoded by the host’s genome) AIRE (Autoimmune regulator) AIRE regulates the expression of ubiquitous self antigens & a wide variety of tissue-restricted self Ag (e.g. pancreas, brain) at low levels in the thymus

Microenvironment MHC restriction Self tolerance affinity 47

T cell development Central tolerance The presence of AIRE medulary cells Central tolerance The presence of autoreactive lymphocytes in periphery

The development of lymphocytes 重要性 細胞 地點 時間 如何運作 結果 特性 比較異同

Adaptive immunity 1. Antigen specificity 2. Diversity 3. Immunological memory 4. Self tolerance

Techniques Adoptive transfer 51

Techniques Hormone Transgenic mice Fertilized egg Transgene

Hybridoma TCR transgene

Knock-out mice

Knock-out mice

黑 白 Knock-out mice Knock-in mice Lethal effect

Positive selection MHC II restriction: Interaction of CD4 with MHCII Host 57

Inducible knock-out mice Tissue specificity Cre/lox system Enzyme (recombinase) in other tissues