Class I histocompatibility antigen display is defective in the RMA-S mutant cell line due to a mutation in the Tap-2 gone, which encodes a peptide transporter. Incubation of RMA-S cells with oligomycin, an inhibitor of mitochondrial ATPase, strongly increased lysis by cytotoxic T lymphocytes (CTL) specific for the class Ib antigen H2-M3, and lysis by Qa-1b-specific CTL was restored. Oligomycin did not affect normal class I display on RMA cells. Treatment of RMA-S cells with other inhibitors of mitochondrial function failed to increase lysis by anti-H2-M3 or Qa-1b CTL. Lysis by allogenic CTL specific for H-2b antigens was either not enhanced or only weakly increased, depending upon the H-2 haplotype of the alloreactive effector cells used.
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