Gamma delta T lymphocytes and proinflammatory cytokines in bacterial meningitis.

Background: Patients with bacterial meningitis have a T-cell defect and impaired cytokine production.

Methods: The phenotype and percentage of circulating alpha beta and gamma delta T-cell receptor-bearing lymphocytes were determined from patients with bacterial meningitis (Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis), patients with bacterial infection but without meningitis, and healthy control subjects by a monoclonal antibody staining method. The in vitro production of cytokines, interleukins (IL-2, IL-6), interferon-gamma and tumor necrosis factor-alpha was measured by the bioassay or ELISAs.

Results: The percentage of circulating gamma delta T cells with a CD3+CD4+CD8- phenotype was significantly (p < 0.001) increased in all patients with bacterial meningitis compared with patients with bacterial infection and healthy control subjects. The CD3+ gamma delta T cells from patients with meningitis produced highly elevated levels of two proinflammatory cytokines, tumor necrosis factor-alpha and IL-6. However, interferon-gamma production was enhanced by CD3+ alpha beta T cells.

Conclusion: The increased percentage of circulating T-cell receptor gamma delta T cells and their in vitro production of tumor necrosis factor-alpha and IL-6 cytokines may play an important role in the pathogenesis and inflammatory response in bacterial meningitis.