Sca-2 Stem cell antigen 2, thymic shared antigen 1 (TSA-1)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
Thymocyte, Immature
Precursor Cell
Bone Marrow
B Cell, Mature

Sca-2 is expressed on intrathymic lymphoid precursors, immature thymocytes, B220+ bone marrow cells and mature B cells, but is absent from mature thymocytes and peripheral T cells.

Sca-2 is a small Cys-rich GPI-linked glycoprotein containing a single Ly-6 domain.

Sca-2 ligands are unknown.

Fetal thymic organ cultures repopulated with very early pre-T cells, CD44-CD25-TCRab-CD4-CD8-  and treated with MTS 35, anti-TSA-1/Sca-2 mAb, show a skewed development towards TCRab+CD4-CD8+  cells, and a decreased number of TCRab+CD4+CD8- cells.  This suggests a role for Sca-2 in the positive selection of thymocytes or lineage commitment towards the CD4+ or CD8+ pathways.

The deduced aa sequences of Sca-2 and TSA-1 are identical, except at position -7 within the N-terminal leader sequence.  A Gly-residue has been reported for Sca-2 and an Arg-residue has been reported for TSA-1.  The mouse Sca-2 locus is linked to Ly6 on chromosome 15.

Database accession numbers

Revised June 25, 2008

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