| Abstrakt: |
In this report we provide evidence for the expression of antigenic epitopes on mouse (β-microglobulin β) that result from assembly with cognate H-2 class I heavy chains. For the cell line 69.9.15 (βm × βm), which expresses a mutant cytosolic form of H-2K and wild-type H-2D, flow cytometry with rabbit antiserum against mouse βm displayed βm expression by cells grown in the presence or absence of fetal calf serum. By contrast, the epitopes identified by the βm-specific monoclonal antibody (mAb) S19.8 and clone 23 were not expressed by 69.9.15 cells grown in serum-containing conditions, and although S19.8 reactivity was weakly recovered by culture in the absence of serum, no such reacitivity was observed with clone 23. Strong expression of these epitopes was achieved following transfection of 69.9.15 cells with the wild-type H-2K gene, indicating that the βm epitopes defined by mAb S19.8 and clone 23 were expressed when βm was assembled with an appropriate heavy chain. In support of this conclusion, we observed the recovery of the S19.8 and clone 23 epitopes by in vitro assembly of H-2K heavy chains with βm in the presence of the VSV N protein p52-59; however, such epitopes were expressed neither by βm prior to heterodimer assembly nor by non-conformed βm present in tissue culture supernatants recovered from H-2 class I surface positive cells. Taken together, these data indicate that in addition to the property of βm to modify the antigenicity of the MHC class I heavy chains, βm epitopes are induced in a reciprocal manner by assembly with MHC class I heavy chain molecules. [ABSTRACT FROM AUTHOR] |
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