these findings suggest that in a primary immune response , in vivo precursors of th cells recognize processed antigen on f1 antigen-presenting cells ( clones restricted to each parental h-2 genotype are cross-sensitized ) under conditions in which those of ctl only respond directly to foreign minor alloantigens on the injected stimulator cells ( clones restricted to parental h-2 genotypes are not cross-immunized ) .
C0018956
precursors
C0007634
cells