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