Hg. Ljunggren et al., DIFFERENTIAL REACTIVITY OF RESIDUAL CD8(-LYMPHOCYTES IN TAP1 AND BETA-2-MICROGLOBULIN MUTANT MICE() T), European Journal of Immunology, 25(1), 1995, pp. 174-178
TAP1 -/- and beta 2-microglobulin (beta 2m) -/- mice (H-2(b) backgroun
d) express very low levels of major histocompatibility complex (MHC) c
lass I molecules on the cell surface. Consequently these mice have low
numbers of mature CD8(+) T lymphocytes. However, TAP1 -/- mice have s
ignificantly higher numbers of CD8(+) T cells than beta 2m -/- mice. A
lloreactive CD8(+) cytotoxic T lymphocyte (CTL) responses were also st
ronger in TAP1 -/- mice than in beta 2m -/- mice. Alloreactive CTL gen
erated in TAP1 -/- and beta 2m -/- mice cross-react with H-2(b)-expres
sing cells. Surprisingly, such cross-reactivity was stronger with allo
reactive CTL from beta 2m -/- mice than with similar cells from TAP1 -
/- mice, The beta 2m -/- mice also responded more strongly when primed
with and tested against cells expressing normal levels of H-2(b) MHC
class I molecules. Such H-2(b)-reactive CD8(+) CTL from beta 2m -/- mi
ce but not from TAP1 -/- mice also reacted with TAP1 -/- and TAP2-defi
cient RMA-S cells. In contrast, H-2(b)-reactive CD8(+) CTL from neithe
r beta 2m -/- mice nor TAP1 -/- mice killed beta 2m -/- cells. In line
with these results, beta 2m -/- mice also responded when primed and t
ested against TAP1 -/- cells. We conclude that the reactivity of resid
ual CD8(+) T cells differs between TAP1 -/- and beta 2m -/- mice. The
MHC class I-deficient phenotype of TAP1 -/- and beta 2m -/- mice is no
t equivalent: class I expression differs between the two mouse lines w
ith regard to quality as well as quantity. We propose that the differe
nces observed in numbers of CD8(+) T cells, their: ability to react wi
th alloantigens and their cross-reactivity with normal H-2(b) class I
are caused by differences in the expression of MHC class I Ligands on
selecting cells in the thymus.