J. Bilsborough et al., Identification of a second major tumor-specific antigen recognized by CTLson mouse mastocytoma P815, J IMMUNOL, 162(6), 1999, pp. 3534-3540
Murine mastocytoma P815 induces CTL responses against at least four distinc
t Ags (AB, C, D, and E), Recent studies have shown that the main component
of the CTL response against the P815 tumor is targeted against Ags P815AB a
nd P815E, The gene PIA has been well characterized, It encodes the P815AB A
g in the form of a nonameric peptide containing two epitopes, P815A and P81
5B, which are recognized by different CTLs. Here, we report the identificat
ion of the P815E Ag, Using a cDNA library derived from tumor P815, we ident
ified the gene coding for P815E. We also characterized the antigenic peptid
e that anti-P815E CTLs recognize on the MHC class I molecule H-2K(d), The P
815E Ag results from a mutation within an ubiquitously expressed gene encod
ing methionine sulfoxide reductase, an enzyme that is believed to be import
ant in the protection of proteins against the by-products of aerobic metabo
lism Surprisingly, immunizing mice i.p. with syngeneic tumor cells (L1210)
that were constructed to express B7-1 and P815E did not induce resistance a
gainst live P815, even though a strong anti-P815E CTL response was observed
with splenocytes from immunized animals.