Exchange of cell-associated ?2-microglobulin in mouse chimeras

Kimura, Shoji; Tada, Nobuhiko; Liu-Lam, Yen; Hämmerling, Ulrich

doi:10.1007/bf00368547

Cited by 8 publications

(2 citation statements)

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“…It has recently been discovered that ß2 exchange occurs for certain specificities on the cell surface in vivo (Kimura et al, 1983) and in tissue culture (Bernabeu et al, 1984;Kefford et al, 1984). In addition, class I antigen internalization into acidic compartments has been demonstrated by immunofluorescence on T cell surfaces (Tse & Pernis, 1984).…”

Section: Discussionmentioning

confidence: 99%

“…It has been observed that when iodinated /?2m is incubated with papain-solubilized class I complex, the ß2 in the complex equilibrates with iodinated ß2 (Hyafil & Strominger, 1979), presumably through a free heavy-chain intermediate. ß2 exchange also occurs on the surface of living cells in vivo (Kimura et al, 1983). The binding site on the heavy chain for ß2 is highly conserved throughout mammalian evolution, since murine ß2 associates with the human heavy chain upon cell fusion (Jones et al, 1976) as well as upon transfection of class I human genes into mouse cells * This work was supported by Grant Al 10736 from the National Institutes of Health.…”

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Subunit interactions of class I histocompatibility antigens

Parker¹,

Strominger²

1985

Biochemistry

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The kinetics of dissociation of iodinated beta 2-microglobulin (beta 2m) from the papain-solubilized class I histocompatibility antigen HLA-B7 have been investigated. In the presence of unlabeled beta 2m, most of the HLA dissociates according to a single rate constant, whereas in the absence of unlabeled beta 2m, the system approaches an equilibrium dependent upon the initial HLA concentration. When iodinated beta 2m is incubated with unlabeled HLA-B7, the rate of incorporation of beta 2m into the complex is much less dependent on the concentration than is expected for a simple association/dissociation system; instead, the system behaves as if the "activity" (in a thermodynamic sense) of the HLA heavy-chain intermediate cannot surpass a critical concentration. The dissociation rate for each class I specificity is a function of temperature, ionic strength, pH, and the status of the heavy chain (papain solubilized vs. detergent solubilized). High temperature, high ionic strength, and extremes of pH promote dissociation. The intact molecule dissociates about 10 times more slowly than the papain-solubilized molecule. In contrast, the rate of dissociation of all papain-solubilized class I antigens tested falls within the range of about a factor of 2. The presence of the carbohydrate has no effect on the rate of dissociation. The possibility that HLA class I antigen dissociation may occur in vivo within acidic internal vesicles is discussed.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Subunit interactions of class I histocompatibility antigens

Parker¹,

Strominger²

1985

Biochemistry

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Expression of the W6/32 HLA epitope by cells of rat, mouse, human and other species: critical dependence on the interaction of specific MHC heavy chains with human or bovine β₂‐microglobulin

Jefferies

MacPherson

1987

Eur J Immunol

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The HLA class I epitope W6/32 is conformationally dependent on both heavy chain and beta 2-microglobulin (beta 2M). Previously, the W6/32 epitope has been detected in humans and other primates as well as from bovine sources. Two controversial reports suggest the W6/32 epitope is constitutively expressed by either normal or transformed murine cells expressing the Db allele. Here we show that the appearance of the W6/32 epitope in murine cells results from the association of either the Db or Kd gene products with either bovine or human beta 2M. We use congenic mouse strains and hybrid H-2 class I genes between Db and Kb to map the W6/32 epitope to particular amino acid residues in the alpha 2 domain. Subsequently, we show that beta 2M exchange is not confined to murine or human cells in vitro but can be detected after beta 2M injection into a mouse. The data presented suggests that beta 2M exchange takes place at the cell surface under physiological conditions and indicates that MHC class I heavy chains are in an equilibrium between the bound and unbound form of beta 2M.

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