Fig. 4

Lack of antigen competition from immunodominant H-2K ^d -restricted 147–155 epitope-specific CTL response does not result in generation of H-2D ^b -restricted CTL responses in H-2 ^d → H-2 ^d×b chimeras.

Spleen cells from chimeras immunized with NP DNA (A) or NPmut DNA (B) were in vitro restimulated with F1 spleen cells pulsed with H-2D^b peptide NP366–374 or H-2K^d peptide NP147–155 for 7 days, and used as effector cells against EL4 cells pulsed with H-2D^b peptide NP366–374 or P815 cells pulsed with H-2K^d peptide NP147–155 in a cytotoxicity assay. Open circles represent the lysis of P815 cells pulsed with H-2K^d peptide by the spleen cells restimulated with H-2D^b peptide (allele-mismatched restimulation) and closed circles represent the lysis of P815 cells pulsed with H-2K^d peptide by the spleen cells restimulated with H-2K^d peptide (allele-matched restimulation). Open triangles represent the lysis of EL4 cells pulsed with H-2D^b peptide by the spleen cells restimulated with H-2K^d peptide (allele-mismatched restimulation) and closed triangles represent the lysis of EL4 cells pulsed with H-2D^b peptide by the spleen cells restimulated with H-2D^b peptide (allele-matched restimulation). The data shown are representative of two independent experiments. The percent lysis by the spleen cells from mock-immunized control mice, and the percent lysis of the nonspecific control targets (P815 cells pulsed with NP366–374 peptide or EL4 cells pulsed with 147–155 peptide) ranged from 3% at an E:T ratio of 7.1:1 to 20% at an E:T ratio of 60:1 (results not shown). The NPmut construct encodes a full-length NP protein containing a tyrosine-to-glycine change at residue 148 and a valine-to-aspartic acid change at 155 (putative anchor positions, see Fig. 1A for details).