Figure 5.  Qa1 molecules expressed on T2Q cells are functional as shown by their recognition by Qa1-specific CTL
			Type 1 CTL		Type 2 CTL
			clones		clone d12i
		T2
		T2-Ld
		T2Q
		L
		LQ
			Lytic units/thousand effectors
T2 cells transfected with Qa1 [T2Q] were incubated with graded doses of Qa1-specific CTL clones
and susceptibility to lysis calculated by regression analysis of the linear part of the dose-response.
Controls included untransfected T2 cells, T2 cells transfected with Ld, L cells, and L cells
transfected with Qa1.
Conclusions
1.  T2Q cells are highly susceptible to lysis by various Qa1-specific CTL clones, showing that
at least some of the Qa1 molecules expressed on these cells are in a correctly conformed state.
2.  All of the Qa1-specific CTL clones that recognize T2Q cells are "type1".  Type 1 clones are able
to recognize Qa1 expressed on H-2b target cells but not on H-2k target cells, and have sometimes
been referred to as Qdm-dependent, but since T2Q cells have no known source of the Qdm peptide
the results shown here demonstrate that this terminology is incorrect, such clones apparently being
able to recognize empty Qa1 molecules.
3.  By contrast, the "type 2" clone, d12i, was completely unable to recognize the Qa1 molecules
on T2Q cells.  Type 2 clones are sometimes referred to as Qdm-independent because they can
recognize Qa1 molecules expressed on both H-2b and H-2k targets.  However, the results shown
above indicate, ironically, that the key difference between type 1 and type 2 clones is that the latter
are absolutely dependent on the presence of an appropriate peptide in the binding groove of Qa1.