P. Bousso et al., Pacing two T cell epitopes: A degree of randomness in the primary responseis lost upon secondary immunization, J IMMUNOL, 165(2), 2000, pp. 760-767
We have analyzed the hierarchy of epitope-specific T cell populations durin
g a primary and a secondary CD8 T cell response. MHC-peptide tetramers were
used to track the in vivo kinetics of expansion of T cell populations spec
ific for two K-d-restricted epitopes simultaneously presented by a murine t
umor cell following primary or recall immunizations. Individual syngeneic m
ice generated remarkably different primary CTL responses, as reflected by u
p to 60-fold differences in the relative contribution of each peptide-speci
fic T cell population to the overall response. In these primary immunizatio
ns, the CTL dominance was not dictated by the respective abundance of the p
resented epitopes, In sharp contrast, the secondary response was systematic
ally associated with a selective expansion of the same epitope-specific pop
ulation both in vitro and in vivo. In vitro experiments indicated that the
extent of expansion of each epitope-specific memory population is modulated
by the epitope density. We conclude that, at least for this set of epitope
s, the CTL hierarchy is not controlled by the same parameters in a primary
vs a secondary response.