Commensal microbes and hair follicles coordinately drive Treg migration

into neonatal skin

Tiffany Scharschmidt, M.D.

Assistant Professor

Department of Dermatology

University of California, San Francisco

How do host and commensals cooperate early in life to promote immune tolerance and a healthy symbiotic relationship?

Neonatal Life

Images adapted from Tamburini et al. Nat Med (2016)

Scharschmidt et al. Immunity (2015)

Tolerance to skin commensals is preferentially established in neonatal life

Neonatal skin Tregs are required to establish tolerance

A wave of Tregs into neonatal skin mediates tolerance to commensals

S. epidermidis

+ ImmuneTolerance

S. epidermidis

+Failure toestablish tolerance

Critical window

What drives migration of Tregs into neonatal skin?

This is a busy time for skin…

HF

HF HF

Hair follicle morphogenesis

Day 6

Day 13

Neonatal Tregs

localize to hair folliclesMicrobial Colonization

Belkaid & Naik. Nat Imm (2013)

Day 13 FoxP3

Hypothesis: Chemokine(s) produced by developing hair follicles direct Treg migration into neonatal skin and

commensal microbes augment this process.

Does hair follicle morphogenesis drive accumulation of Tregs in neonatal skin?

K5/Dkk1 neonates have disrupted HF development and fewer skin Tregs

Do commensal microbes drive accumulation of

Tregs in neonatal skin?

Treg accumulation is significantly and preferentially reduced in germ-free neonates

What are the molecular mechanisms that

mediate accumulation of Tregs in neonatal skin?

Combined discovery approach to identify chemokine-receptors pairs mediating neonatal skin Treg accumulation

RNAseq D13 Skin vs. LN TregsChemokine qPCR array D6 vs. D13 skin

Receptors on neonatal skin TregsSkin chemokines expressed in this window

Chemokine qPCR array D13 SPF vs. GF skin

Skin chemokines augmented by commensals

Ccl20/Ccr6

Commensals augment expression of Ccl20 in developing HFs

D13 SPF

Ccl20 reduced in GF skin

RNA in situ hybrid. showsCcl20 in HF keratinocytes

Do neonatal skin Tregs express cognate receptor CCR6?

Ccr6 is preferentially expressed by neonatal skin Tregs

Can Ccl20/Ccr6 drive neonatal Treg migration?

Ccl20 preferentially drives neonatal Tregs migration in vitro

D10 Thymic CD4+

Chemokine

3h

Analyze flow-through to assess Treg migration

Ccr6 promotes skin Treg accumulation in neonatal adoptive transfer

i.p. injection1.5M CD45.1 WTCD4+ thymocytes

D9 rag2-/-

Harvest skin, SDLN, spleen2wk post-transfer

1.5M CD45.2 Ccr6-/-

CD4+ thymocytes

Gated onCD4+ FoxP3+

Hair Follicle

Development

Commensals and developing HFs coordinately direct Tregs to skin during the optimal window for commensal-specific tolerance

How do specific commensals and commensal products shape the hair follicle

immune environment?

Acknowledgments

MentorsMichael RosenblumMichael Fischbach

Abul Abbas

Scharschmidt LabKimberly VasquezElizabeth Leitner

Kevin Chu

Rosenblum LabMariela Pauli

Niwa AliMaggie Lowe

CollaboratorsJustin Sonnenburg (Stanford)

Sarah Millar (Upenn)James Moon (MGH)

Elizabeth Grice (UPenn)Michael Otto (NIH)

Jan Liese (Germany)

Funding

scharschmidtlab.ucsf.edu