Fibroblastic Reticular Cells in Secondary Lymphoid Organs

Mechthild Lütge

PhD Defense, 22.03.2024

University of Zurich

Lymph Nodes

Spleen

Peyer's patches

Secondary Lymphoid organs (SLO)

Dedicated sites where adaptive immunity is mounted to pathogens in the lymph, blood or intestine

Fibroblastic reticular cells orchestrate SLO organization

Acton et al. Trends in Immunology, 2021

Acton et al. Trends in Immunology, 2021

Fibroblastic reticular cells (FRC) form specialized immune cell niches to support adaptive immune responses

Fibroblastic reticular cells orchestrate SLO organization

Fibroblastic reticular cells orchestrate SLO organization

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Fibroblastic reticular cells orchestrate SLO organization

Migration

created with biorender.com

Fibroblastic reticular cells orchestrate SLO organization

Migration

Activation

and survival

created with biorender.com

Fibroblastic reticular cells orchestrate SLO organization

Migration

Activation

and survival

Extracellular matrix

created with biorender.com

Fibroblastic reticular cells orchestrate SLO organization

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

Fibroblastic reticular cells orchestrate SLO organization

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

→ Modulators of immune responses:

Strength and specificity of immune response

Fibroblastic reticular cells orchestrate SLO organization

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

→ Modulators of immune responses:

Strength and specificity of immune response

→ Prototypic immune-interacting fibroblast

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

Fibroblastic reticular cells as prototypic immune-interacting fibroblasts

→ Modulators of immune responses:

• Vaccine efficacy

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

Fibroblastic reticular cells as prototypic immune-interacting fibroblasts

→ Modulators of immune responses:

• Autoimmunity and inflammatory disorders

• Vaccine efficacy

Migration

Activation

and survival

Extracellular matrix

Antigen presentation

and immune cell interaction

created with biorender.com

Fibroblastic reticular cells as prototypic immune-interacting fibroblasts

→ Modulators of immune responses:

• Autoimmunity and inflammatory disorders
• Antitumor immuntity

• Vaccine efficacy

Fibroblastic reticular cells orchestrate SLO organization

Acton et al. Trends in Immunology, 2021

Acton et al. Trends in Immunology, 2021

Fibroblastic reticular cells orchestrate SLO organization

Antigen sampling zone:

- Marginal reticular cells (MRCs)

Acton et al. Trends in Immunology, 2021

Fibroblastic reticular cells orchestrate SLO organization

Antigen sampling zone:

- Marginal reticular cells (MRCs)

Acton et al. Trends in Immunology, 2021

B cell follicle:

- Follicular dendritic cells (FDCs)

Fibroblastic reticular cells orchestrate SLO organization

Antigen sampling zone:

- Marginal reticular cells (MRCs)

Acton et al. Trends in Immunology, 2021

B cell follicle:

- Follicular dendritic cells (FDCs)

T-B border region:

- T-B border reticular cells (TBRCs)

Fibroblastic reticular cells orchestrate SLO organization

Antigen sampling zone:

- Marginal reticular cells (MRCs)

Acton et al. Trends in Immunology, 2021

B cell follicle:

- Follicular dendritic cells (FDCs)

T-B border region:

- T-B border reticular cells (TBRCs)

T cell zone:

- T cell zone reticular cells (TRCs)

Fibroblastic reticular cells orchestrate SLO organization

Antigen sampling zone:

- Marginal reticular cells (MRCs)

Acton et al. Trends in Immunology, 2021

B cell follicle:

- Follicular dendritic cells (FDCs)

T-B border region:

- T-B border reticular cells (TBRCs)

T cell zone:

- T cell zone reticular cells (TRCs)

Perivascular space:

- Perivascular reticular cells (PRCs)

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

(2.) Species?

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

(2.) Species?

​(3.) Activation?

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

(2.) Species?

​(3.) Activation?

→ What factors shape FRC subset identity and function?

Fibroblastic reticular cells orchestrate SLO organization

• Conserved stromal–immune cell circuits secure B cell homeostasis and function

Fibroblastic reticular cells orchestrate SLO organization

B cell zone reticular cells direct efficient humoral immunity

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

B cell zone reticular cells direct efficient humoral immunity

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

B cell zone reticular cells direct efficient humoral immunity

• to what extend are BRC underpinned niches functionally conserved across SLO?

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

B cell zone reticular cells direct efficient humoral immunity

• to what extend are BRC underpinned niches functionally conserved across SLO?

• Systemic humoral immunity?

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

B cell zone reticular cells direct efficient humoral immunity

• to what extend are BRC underpinned niches functionally conserved across SLO?

• Systemic humoral immunity?

• What are major pathways controlling BRC-immune cell interactions?

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

B cell zone reticular cells direct efficient humoral immunity

• to what extend are BRC underpinned niches functionally conserved across SLO?

• Systemic humoral immunity?

• What are major pathways controlling BRC-immune cell interactions?

• Are these interactions functionally redundant across SLOs?

CXCL13  CCL19/CCL21

CXCL13+ FRC = B cell zone reticular cells (BRCs)

Shared B cell follicle and PI16+ BRC subset identity across SLOs

Onder L et al., Immunity, 2017

Lütge et al. Nat. Immunol., 2023

Shared B cell follicle and PI16+ BRC subset identity across SLOs

Onder L et al., Immunity, 2017

Lütge et al. Nat. Immunol., 2023

Shared B cell follicle and PI16+ BRC subset identity across SLOs

Onder L et al., Immunity, 2017

Lütge et al. Nat. Immunol., 2023

Shared B cell follicle and PI16+ BRC subset identity across SLOs

Onder L et al., Immunity, 2017

Lütge et al. Nat. Immunol., 2023

Developmental and anatomical gene sets imprint BRC identity

Lütge et al. Nat. Immunol., 2023

Developmental and anatomical gene sets imprint BRC identity

Lütge et al. Nat. Immunol., 2023

Developmental and anatomical gene sets imprint BRC identity

Lütge et al. Nat. Immunol., 2023

Subset identity

Developmental and anatomical gene sets imprint BRC identity

Lütge et al. Nat. Immunol., 2023

→ Organ-specific gene sets reflect developmental and anatomical imprints

Subset identity

Niche factors and signaling pathways define subset identity and function

Lütge et al. Nat. Immunol., 2023

Subset-specific niche factors

Subset-specific signaling pathways

Niche factors and signaling pathways define subset identity and function

Lütge et al. Nat. Immunol., 2023

→ Subset-specific gene sets that are consistently found across SLOs point to BRC modulation by immune cells

Subset-specific niche factors

Subset-specific signaling pathways

Conserved feedforward BRC-immune cell circuits sustain functional BRC niches

Lütge et al. Nat. Immunol., 2023

→ BRC-derived niche factors determine immune cell function

Conserved feedforward BRC-immune cell circuits sustain functional BRC niches

Lütge et al. Nat. Immunol., 2023

→ BRC-derived niche factors determine immune cell function

→ Leukocyte-derived maturation factors specify BRC subset identity

→ Conserved in humans

Conserved feedforward BRC-immune cell circuits sustain functional BRC niches

Lütge et al. Nat. Immunol., 2023

→ BRC-derived niche factors determine immune cell function

→ Leukocyte-derived maturation factors specify BRC subset identity

→ Conserved in humans

→ Validation?

Immune cell-derived maturation cues drive BRC differentiation and activation

Lütge et al. Nat. Immunol., 2023

FDC

B cell

PI16+RC

Mph/DC

T cell

Immune cell-derived maturation cues drive BRC differentiation and activation

Lütge et al. Nat. Immunol., 2023

FDC

B cell

PI16+RC

Mph/DC

T cell

CR2

ICAM1

IL6

Immune cell-derived maturation cues drive BRC differentiation and activation

Lütge et al. Nat. Immunol., 2023

CR2

IL1b

IL4

ICAM1

TGFb

PGRN

TGFb

FDC

B cell

PI16+RC

Mph/DC

T cell

IL6

Summary - 1: Advanced understanding of systemic humoral immunity

Lütge et al. Nat. Immunol., 2023

Lymph node

Spleen

Peyer's patch

Organ-specific imprints

Summary - 1: Advanced understanding of systemic humoral immunity

Lütge et al. Nat. Immunol., 2023

Lymph node

Spleen

Peyer's patch

Organ-specific imprints

Functional convergence

Summary - 1: Advanced understanding of systemic humoral immunity

Lütge et al. Nat. Immunol., 2023

Lymph node

Spleen

Peyer's patch

Organ-specific imprints

Functional convergence

Feedforward paradigm: circulating immune cell imprint B cell follicle niches in an organ indiscriminate manner thereby securing efficient systemic humoral immunity

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

(2.) Species?

​(3.) Activation?

→ What factors shape FRC subset identity and function?

Fibroblastic reticular cells orchestrate SLO organization

To what extend are FRC underpinned niches functionally conserved across:

(1.)  SLOs?

(2.) Species?

​(3.) Activation?

→ What factors shape FRC subset identity and function?

Fibroblastic reticular cells orchestrate SLO organization

• PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Lymph node structure

Capsule

B cell follicle

afferent lymphatics

efferent lymphatics

Subcapsular sinus

Paracortex

Medulla

blood vasculature

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Repeated lymph node expansion and contraction throughout life

• Rapid expansion allows massive lymphocyte entry and proliferation

• Structural and functional tissue integrity is preserved

• FRC stretching and proliferation regulate network tension

Assen et al. Nat. Immunol., 2022

Repeated lymph node expansion and contraction throughout life

• Rapid expansion allows massive lymphocyte entry and proliferation

• Structural and functional tissue integrity is preserved

• FRC stretching and proliferation regulate network tension

Assen et al. Nat. Immunol., 2022

→ How does repeated expansion and contraction in response to immunological stimuli shape the FRC network in human lymph nodes?

Repeated lymph node expansion and contraction throughout life

• Rapid expansion allows massive lymphocyte entry and proliferation

• Structural and functional tissue integrity is preserved

• FRC stretching and proliferation regulate network tension

→ How does repeated expansion and contraction in response to immunological stimuli shape the FRC network in human lymph nodes?

→ Stereotypic "resting" lymph node?

Assen et al. Nat. Immunol., 2022

The FRC landscape in human palatine tonsils

De Martin et al. Nat. Immunol., 2023

The FRC landscape in human palatine tonsils

De Martin et al. Nat. Immunol., 2023

The FRC landscape in human palatine tonsils

De Martin et al. Nat. Immunol., 2023

• Heterogenous FRC subsets similar to murine SLOs

The FRC landscape in human palatine tonsils

De Martin et al. Nat. Immunol., 2023

• Heterogenous FRC subsets similar to murine SLOs

The FRC landscape in human palatine tonsils

De Martin et al. Nat. Immunol., 2023

• Heterogenous FRC subsets similar to murine SLOs

• Subepithelial PI16+ reticular cells show the strongest inflammation induced remodeling

De Martin et al. J Exp Med., 2024

The FRC landscape in human palatine tonsils

De Martin et al. J Exp Med., 2024

• Heterogenous FRC subsets similar to murine SLOs

• Subepithelial PI16+ reticular cells show the strongest inflammation induced remodeling

• PI16+ reticular cells integrate immune cell-derived signals and govern T cell activation

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

→  How does inflammatory activation affect the human lymph node FRC landscape?

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

→  How does inflammatory activation affect the human lymph node FRC landscape?

→ Are PI16+ RCs involved in inflammatory reactions of human lymph nodes?

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

→  How does inflammatory activation affect the human lymph node FRC landscape?

→ Are PI16+ RCs involved in inflammatory reactions of human lymph nodes?

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

→  How does inflammatory activation affect the human lymph node FRC landscape?

→ Are PI16+ RCs involved in inflammatory reactions of human lymph nodes?

• Resting:

clinically not inflamed lymph nodes from patients with benign tumors

Objectives

→ Characterization of the FRC landscape in a stereotypic "resting" human lymph node

→  How does inflammatory activation affect the human lymph node FRC landscape?

→ Are PI16+ RCs involved in inflammatory reactions of human lymph nodes?

• Resting:

• Activated: 

clinically not inflamed lymph nodes from patients with benign tumors

acute or chronically inflamed lymph nodes

Immunoanatomy of resting human lymph nodes

CD20: B cells

CD3: T cells

ACTA2: Vascular smooth muscle cells/FRCs

Immunoanatomy of resting human lymph nodes

CD20: B cells

CD3: T cells

ACTA2: Vascular smooth muscle cells/FRCs

Immunoanatomy of resting human lymph nodes

CD20: B cells

CD3: T cells

ACTA2: Vascular smooth muscle cells/FRCs

Immunoanatomy of resting human lymph nodes

CD20: B cells

CD3: T cells

ACTA2: Vascular smooth muscle cells/FRCs

Distinct FRC subsets form the perivascular niche in human lymph nodes

Distinct FRC subsets form the perivascular niche in human lymph nodes

• Strong overlap with FRC landscape in human tonsils

Distinct FRC subsets form the perivascular niche in human lymph nodes

• Strong overlap with FRC landscape in human tonsils

• PI16+RCs, PRCs and VSMCs share the expression of genes involved in vascular support

Distinct FRC subsets form the perivascular niche in human lymph nodes

• Strong overlap with FRC landscape in human tonsils

• PI16+RCs, PRCs and VSMCs share the expression of genes involved in vascular support → Localization?

PI16+RCs support the subcapsular sinus and large arteries in the medulla

PI16+RCs support the subcapsular sinus and large arteries in the medulla

PI16+RCs support the subcapsular sinus and large arteries in the medulla

PI16+RCs support the subcapsular sinus and large arteries in the medulla

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

• All FRC subset are conserved upon chronic activation

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

• All FRC subset are conserved upon chronic activation

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

• All FRC subset are conserved upon chronic activation
• PI16+RCs support tissue remodelling in inflamed human lymph nodes → immune cell interactions?

PI16+ RCs support inflammation-induced remodeling in human lymph nodes

• All FRC subset are conserved upon chronic activation
• PI16+RCs support tissue remodelling in inflamed human lymph nodes → immune cell interactions?

PI16+ RCs form reactive immune cell niches

• Bidirectional crosstalk between PI16+RCs and immune cells

• Bidirectional crosstalk between PI16+RCs and immune cells

Immune cell-provided activation cues

PI16+ RCs form reactive immune cell niches

• Bidirectional crosstalk between PI16+RCs and immune cells

Immune cell-provided activation cues

PI16+ RCs form reactive immune cell niches

Immune cell-provided activation cues

PI16+ RCs form reactive immune cell niches

Inferred interactions upon lymph node activation:

• PI16+RCs integrate activation cues from macrophages and dendritic cells

PI16+RC-provided immune-modulation cues

PI16+ RCs form reactive immune cell niches

Inferred interactions upon lymph node activation:

• PI16+RCs integrate activation cues from macrophages and dendritic cells

PI16+RC-provided immune-modulation cues

PI16+ RCs form reactive immune cell niches

Inferred interactions upon lymph node activation:

• PI16+RCs integrate activation cues from macrophages and dendritic cells

PI16+RC-provided immune-modulation cues

PI16+ RCs form reactive immune cell niches

Inferred interactions upon lymph node activation:

• PI16+RCs integrate activation cues from macrophages and dendritic cells

• PI16+RCs provide immune modulatory cues to macrophages and dendritic cells

PI16+RC-provided immune-modulation cues

→ Validation?

PI16+ RCs form reactive immune cell niches

Inferred interactions upon lymph node activation:

• PI16+RCs integrate activation cues from macrophages and dendritic cells

• PI16+RCs provide immune modulatory cues to macrophages and dendritic cells

PI16+ RCs form reactive immune cell niches

• Perivenous PI16+RCs in activated human lymph nodes

PI16+ RCs form reactive immune cell niches

• Perivenous PI16+RCs in activated human lymph nodes

• Surface contact between PI16+RCs and CD11c+myeloid cells

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Summary II: PI16+ reticular cells form reactive immune cell niches in human lymph nodes

Burkhard Ludewig Group

Lisa Kurz

Angelina De Martin

Nadine Cadosch

Christian Perez-Shibayama

Cristina Gil-Cruz

Hung-Wei Cheng

Lucas Onder

Natalia Pikor Group

Sarah Grabherr
 

Acknowledgements

Department of

Otorhinolarnygology (KSSG)

Sandro Stöckli

Yves Stanossek

Samuel Meili

PhD Committee

Burkhard Ludewig

Mark D. Robinson

Maries van den Broek

University of Zurich

Charlotte Soneson

Almut Lütge

University of Pennsylvania

Joshua Brandstadter

Ivan Maillard