CD8+ T Cells Have a Decreased Requirement for Activation Late After Burn Injury

Abstract

Burn injury initially suppresses T cell responses but later after injury CD8+ T cells are hyper-responsive to specific and non-specific stimuli, possibly due to the generation of memory CD8+ T cells. Given that the requirement for costimulation (e.g. B7-CD28 interactions) is much less in memory T cells than in naïve T cells, in this study we hypothesize that costimulation requirements for CD8+ T cell activity late after burn injury. In this study, we test this hypothesis with two different models of costimulation-dependency in purified murine CD8+ T cells. Female C57BL/6 mice transgenic for the HY male antigen were subjected to 20% TBSA contact burn. We sacrificed mice 14 days after injury and purified viable CD8+ T cells using negative magnetic separation eliminating CD4+, MHC Class II+, and CD11b+ cells. We used two methods to stimulate purified CD8+ T cells. First, 1 × 10 6 cells were stimulated with soluble MHC Class I tetramer bearing HY peptide, which is known to activate T cells without signal two. Next we incubated 1 × 10 6 cells with limiting amounts of anti-CD3 antibody in the presence or absence of costimulatory anti-CD28 antibody. Proliferation was measured by standard [3H]-thymidine uptake and data compared by Student's t-test with significance defined as p<0.05.