Figure 13.  100-1000 fold higher concentrations of peptide are required to sensitize RMA/S cells, compared to T2Q cells, to lysis by CTL
		Lytic units/thousand effectors
Various concentrations of Qdm peptide were added into cytotoxicity assays containing T2Q or
RMA/S cells together with graded doses of CTL.  Susceptibility to lysis was calculated by
regression analysis and the amount of killing relative to that in the presence of saturating
amounts of peptide was plotted.
Conclusions
1.  In this experiment 50% maximal lysis of T2Q cells by d12i cells occurred at 0.3nM Qdm,
whereas 50% maximal lysis of RMA/S cells required 300nM Qdm.
2.  50% maximal lysis of RMA/S cells by the type 1 CTL clone a2d required 30nM.
3.  The much higher concentrations of peptide required to sensitize RMA/S cells to lysis by CTL
reflect the much lower concentration of Qa1 molecules expressed on RMA/S and murine cells in
general [see Figures 1 and 7] compared to the levels expressed on T2Q cells, and explain why
Qdm peptide can protect T2Q but not RMA/S cells from lysis by Qa1R +ve NK cells.