Flow cytometric measurement of rat lymphocyte subpopulations after burn injury and burn injury with infection

D. G. Burleson, G. K. Vaughn, A. D. Mason Jr and B. A. Pruitt Jr

Increased infection rates in burned patients may result from a disproportionate increase in the suppressor subpopulations. Measurement of lymphocyte subpopulations is difficult in burned patients because gradient-purified cells are contaminated by nonlymphoid cells. The accuracy of flow cytometric subpopulation analysis was improved by restricting (gating) the analysis to cells with light-scatter intensity typical of lymphocytes. Blood was obtained 48 hours after burn from rats receiving no burns, 30% scald burns, or burns seeded with Pseudomonas aeruginosa to induce infection. Subpopulations were identified by monoclonal antibodies to T-lymphocyte antigens. Gating increased the values obtained for most subpopulations, but the relative differences between groups were unchanged. Burned and infected animals, but not animals burned only, had a decreased ratio of helper to suppressor lymphocytes (HSR) relative to control. A decreased HSR correlated with sepsis, but not with infection susceptibility. This suggests that a decrease in HSR may be a result of infection rather than a cause of susceptibility to infection.