Robert Tigelaar, MD

Dr. Robert Tigelaar's major research focus continues to be the dendritic epidermal d T cells (DETC) populating the skin of all normal strains of mice. A number of longstanding collaborations between the Tigelaar lab and those of Michael Girardi (Dermatology) and Adrian Hayday (Guy’s Immunobiology [London]) include:

1. The generation and characterization of a Vg5-/- “knockout” mouse selectively deficient in DETCs expressing the TCR prototypically seen on >95% of such cells; studies of such mice unexpectedly showed that in the absence of Vg5, the replacement population of d DETC includes a significant number of cells expressing a Vd1/d1 TCR with a similar 3-D conformation as the conventional Vg5/Vd1 TCR (as defined by an anti-clonotypic antibody to the Vg5/Vd1 TCR)
2. Documentation that some (e.g., FVB and NOD), but not other (B6) strains of mice genetically deficient in d T cells (d-/- mice) develop a localized (ears) cutaneous inflammation/ spontaneous dermatitis (SpD) that is dependent (like atopic dermatitis) both upon conventional aß T cells and upon an appropriate external environment.

Adoptive transfer studies showed that Vg5+ DETC but not systemic Vg5- d cells were necessary and sufficient to down-regulate SpD. Finally, crosses of susceptible (NOD) and resistant (C57BL/6) d-/- mice which showed that susceptibility to SpD behaves as a recessive trait, have been recently analyzed by genome-wide, microsatellite mapping; these studies clearly indicate that several distinct genetic intervals contribute to the regulation of this cutaneous inflammatory response. Ongoing studies in this arena:

1. To characterize in more detail the pathology in SpD normally down-regulated by skin-associated DETC
2. To characterize the genes expressed by “resting” DETC and in vitro “activated” DETC by serial analysis of gene expression (SAGE)
3. To investigate the potentials of selected candidate DETC cytokines/effector molecules to down-regulate SpD

Recent studies of a spontaneous mutation arising in a substrain of FVB mice that results in a striking deficiency in the skin of the prototypic Vg5/Vd1+ DETCs seen in other normal mice strains led to further studies that proved that this heritable defect in a dominant gene resided in fetal thymic epithelial cells resulting in a failure of positive selection in the thymus (and subsequent migration to the skin) of the Vg5/Vd1+ fetal thymic precursors. (These results, published in Nature Immunology, present the first definitive proof that d cells resident in epithelial interfaces with the external environment, like conventional recirculating aß T cells, undergo positive selection in the thymus.) In a productive collaborative followup study between Drs. Tigelaar, Girardi and Hayday with Richard Lifton (Genetics) recently published in Nature Genetics, it was shown that this defect is caused by mutation in Skint1, a newly identified gene expressed in thymus and skin that encodes a protein with immunoglobulin-like and transmembrane domains. Skint1 is the prototypic member of a rapidly evolving family of at least 11 genes in mouse, with greatest similarity to the butyrophilin genes. These findings define a new family of proteins mediating key epithelial-immune interactions.

• Characterizing the genes expressed by "resting" and "activated" DETC by serial analysis of gene expression (SAGE) and comparing such expression patterns with other IEL and recirculating T cell subsets.
• Investigating selected candidate DETC anti-inflammatory cytokines/effector molecules by reconstituting TCR delta-/- recipients with DETC precursors rendered deficient (via gene "knockout" or siRNA "knock-down") in candidate anti-inflammatory molecules.
• Utilizing genome-wide microsatellite mapping, to identify the genetic interval(s), and ultimately the specific genes, controlling susceptibility/resistance to the spontaneous dermatitis that develops in some, but not other TCR delta -/- mice.
• Utilizing cellular, molecular and genetic studies to identify the physiologic ligands for TCR gamma/delta+ T cells that trigger both their positive selection in the thymus and their activation in peripheral epithelial tissues such as the skin and GI tract.