MHC‐I binding peptides and β2 microglobulin (β2‐m) can upregulate the MHC‐I heavy chain expression on certain peptide transporter mutant cells. We have further studied this with normal cells and non‐mutant cell lines. No MHC‐I upregulation was seen with normal, resting or activated T cells. On mouse cell lines P815 and B16, both peptides and human β2‐m gave an additive upregulation response. With the human small cell lung carcinoma H82, an optimal HLA.A2 binding peptide (GILGFVFTL) gave an upregulation response, whereas β2‐m alone or in combination with this peptide had no effect. However, β2‐m potentiated the response of H82 cells to a slightly longer peptide. Using mutant RMA‐S cells, it was found that both Brefeldin A (BFA) and chloroquine, but not leupeptin, inhibited MHC‐I upregulation response to both peptide and β2‐m. In contrast to chloroquine, BFA also gave a reduction of background membrane MHC‐I expression, presumably due to a block in Golgi transport. Human β2‐m, which binds to RMA‐S cells, and which is known to internalize into endosomes, did not reappear on the cell surface. When Db on RMA‐S cells was upregulated by human ft‐m, the sensitivity of these cells to Db restricted CTL cells increased. Even if β2‐m did not upregulate the overall MHC‐I expression on normal cells, it may still quantitatively increase the expression of optimally presented peptides and endosomal recycling may be important in this process.
|Number of pages||6|
|Journal||Scandinavian Journal of Immunology|
|Publication status||Published - Oct 1993|
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