TRAF1 protein is selectively lost from antigen-specific CD8 T cells during chronic, but not acute, LCMV infection. Mice were infected with either acutely infecting LCMV Armstrong (A) or chronically infecting clone 13 (C). Tetramer⁺ (gp33⁺ gp276⁺ NP396⁺) CD8 T cells were sorted on day 7 and 21 after infection, and the pooled purified tetramer⁺ T cells were subjected to either Western blot analysis or semiquantitative RT-PCR analysis. (a) Representative blots of TRAF1, TRAF2, and actin protein levels (left) and summary of TRAF1 and TRAF2 levels normalized to actin for tetramer⁺ T cells isolated from individual mice at the times indicated for the two different viral infections (right). Total CD8 T cells were sorted from uninfected mice (U) as a control. (b) mRNA levels of TRAF1 relative to Actin on the sorted T cells for the indicated viruses and times of infection. Data are representative of three (for protein) or two (for mRNA) independent mouse experiments. Right side of the gel in (b) indicates a titration of the template, indicating nonsaturation of the signal.