Ly-6 Sca-1, TAP, MALA-1
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
Hematopoietic Cell
5 / 20

The 4 mouse Ly-6, leukocyte tyrosine kinase, genes have different expression patterns, as do the alleles of the Ly-6A/E gene.  Ly-6A/E is expressed on hematopoietic stem cells.  The allele Ly-6A.2 is also present on 30% of CD4-/CD8- thymocytes, 50%-70% on peripheral lymphocytes, and on all activated B and T cells.  In contrast, the allele Ly-6E.1 is expressed on only 10%-15% on peripheral lymphocytes and on activated T and B cells.  Ly-6C is expressed on bone marrow cells, monocytes, neutrophils and 50% on peripheral CD8+ T cells. Ly-6G.1 is also expressed in the bone marrow.  Transfection studies suggest that the Ly-6G.1 cDNA does not encode a protein that is recognized by anti-Ly-6B antibodies.  LY-6F.1 mRNA is not detected in the bone marrow, spleen or thymus, but is detected in several non-lymphoid tissues including testes.

Ly-6A/E and Ly-6C are both GPI-anchored glycoproteins.  The Ly-6 gene products share an ~50% aa sequence identity.  The N-termini of Ly-6C.2 and Ly-6E.1 have been confirmed by protein sequencing.  The sites of attachment of the GPI-anchors are not known, but they are predicted to be Asn76/79 based on known attachment sites of similar GPI-anchored proteins.  The Ly-6 antigens are similar to CD59 and presumably have a similar fold.

Cell Type Unreduced Reduced
10 - 14 kDa 14 - 18 kDa


The expression patterns of Ly-6A/E, Ly-6C and Ly-6G suggest a role in the development and maturation of lymphocytes. Anti-Ly-6 antibodies can activate T cells but this generally requires a secondary antibody cross-linking and phorbol esters, and is dependent on TCR/CD3 expression.  This activation requires the GPI-anchor.  B cell activation can be induced by anti-Ly-6 antibodies in the presence of IL-4 and IFNg.  Ly-6 expression is induced in a complex manner by interferons and TNF.

The genetic complex in the mouse Ly-6 locus spans approximately 630 kb and contains at least 18 genes. Hybridization studies show that several of these genes are related to Ly-6.  The Ly-6 lymphoid antigens were originally characterized with allo-antisera, but subsequent cDNA cloning showed that they were the products of 2 genes, namely Ly-6A/E and Ly-6C.  Recently 2 further genes, Ly-6F and Ly-6G, have been identified in the region which are clearly related to Ly-6A/E and Ly-6C.  The mouse thymocyte B cell antigen (ThB) has a sequence homology with ~25% to the Ly-6A/E and Ly-6C molecules and its gene has been mapped to chromosome 15, raising the possibility that it too may lie within the Ly-6 complex.  The gene encoding the antigen Ly-6B has yet to be characterized.  No human Ly-6 homologues have been identified to date.

Database accession numbers

Revised June 25, 2008

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