class I antigens


class I antigens
major histocompatibility antigens found on virtually every cell except for human erythrocytes; they are found on molecules consisting of two noncovalently bound chains. One, a 44-kD polymorphic glycoprotein partially embedded in the cell membrane, is determined by an MHC gene (HLA-A, -B, -C, -E, -F, and -G in humans); the other, β2-microglobulin, a 12-kD nonpolymorphic protein, is determined by a non-MHC gene. The classical class I antigens (HLA-A, -B, and -C, called also class Ia) are recognized during graft rejection and are also the antigens involved in MHC restriction (q.v.). The nonclassical antigens (HLA-E, -F, and -G, called also class Ib) have a different tissue distribution than do the classical antigens; their functions are under investigation.

Medical dictionary. 2011.

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