TAP1 deficiency

The transporter associated with antigen processing (TAP), which is composed of two subunits (TAP1 and TAP2) that have different biochemical and functional properties, plays a key role in peptide loading and the cell surface expression of HLA class I molecules. The TAP1 defect leads to unstable HLA class I molecules and their retention in the endoplasmic reticulum. The absence of TAP1 is compatible with life and do not result in higher susceptibility to viral infections than TAP2 deficiency.

Alternative names


Major histocompatibility complex class I deficiency

Bare Lymphocyte Syndrome type 1


  • Combined B and T cell immunodeficiencies
    • Major histocompatibility complex class I deficiency


Autosomal recessive


#604571 Bare lymphocyte syndrome, type I

*170260 Transporter, atp-binding cassette, major histocompatibility complex,

Cross references

Phenotypically related immunodeficiencies

IDR factfile for TAP2 deficiency


Incidence is not known.