Expression of cytolytic protein-perforin in peripheral blood lymphocytes in severe traumatic brain injured patients.

PURPOSE: The purpose of this study was to investigate the changes of cytotoxic protein-perforin in peripheral blood lymphocytes in severe TBI patients and possible correlation between severity of TBI and perforin expression.

METHODS: Flow cytometry was used for simultaneous detection of intracellular perforin and cell surface antigens of peripheral blood lymphocytes of 20 severe TBI patients on day 1, 4 and 7 after the onset of injury. Peripheral blood mononuclear cells from 20 healthy volunteers were used as control. Clinical and laboratory parameters were also recorded.

RESULTS: There was a statistically significant decrease of perforin-positive lymphocytes including T, natural killer (NK) and NKT cells on day 4 as compared with day 1 after the brain injury or healthy controls. On day 7, perforin expression was restored in lymphocyte of cytotoxic phenotype (CD8(+) T lymphocytes, NK cells, and NKT cells) compared with day 1. High positive correlation was found between the severity of TBI and frequency of perforin-positive cells on day 4 when the occurrence of the intra-hospital infections was the highest.

CONCLUSION: Severe TBI significantly decreases perforin expression in T lymphocytes, NK and NKT cells, which indicate a possible mechanism underlying the high susceptibility to infections.