Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
GPI anchor
T Lymphocyte, Peripheral
T Cell, Mature
20 / 40

RT6 is a specific marker for peripheral T lymphocytes. In the rat, RT6 is expressed on the majority of mature peripheral T cells, but not on thymocytes or any other hematopoietic cells. Recent thymic emigrants are RT6-/Thy-1+ and these mature to RT6+/Thy-1-cells. Intestinal intraepithelial T cells express RT6 at particularly high levels.  At the mRNA level, the expression of mouse RT-6 is similar to that in the rat. The human RT6 gene is transcriptionally inactive.

RT6.1 and RT6.2 are a single chain GPI-anchored glycoproteins.  They are products of separate alleles of the rat RT6 locus.  A proportion of RT6.1 is N-glycosylated.  The cDNA sequences of RT6.1 and RT6.2 differ at 18 positions leading to 12 aa substitutions and the presence of a glycosylation site in the translated sequence of RT6.1.  In the mouse, 2 closely linked genes encode different RT6 proteins, Rt6-1 and Rt6-2, both of which are polymorphic.  The single copy gene for human RT6 is a pseudogene as a result of 3 premature in-frame stop codons.  RT6 shows sequence homology to a family of bacterial toxins that function as mono-ADP-ribosyltransferases.

Cell Type Unreduced Reduced
RT6.1 21 kDa, 23 kDa, 27 - 32 kDa 24 kDa, 27 kDa, 30 - 35 kDa
RT6.2 21 kDa, 24 kDa 25 kDa, 28 kDa

RT6 co-immunoprecipitates with the Src family tyrosine kinases Fyn and Lck in rat T cells.

RT6 has NAD-metabolizing activity and can undergo auto-ADP-ribosylation on arginine residues.  RT6 may also ADP-ribosylate other target proteins at the cell surface thereby modulating their function.  This may help to explain the susceptibility to auto-immune disease of some experimental animals which have deficient RT6 expression.  Incubation of mouse cytotoxic T cells with NAD suppresses their ability to lyse target cells, an effect mediated through a GPI-anchored ADP-ribosyltransferase. This has promoted the speculation that the transferase is RT6, suggesting a possible link between low RT6 expression and enhanced T cell auto-reactivity.


Database accession numbers

Revised June 25, 2008

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