Interferon gamma and tumour necrosis factor alpha are overexpressed in bone marrow T lymphocytes from paediatric patients with aplastic anaemia.

Twelve paediatric patients with aplastic anaemia and two groups of normal control subjects underwent flow cytometric analysis for intracytoplasmic expression of gamma interferon (gamma-IFN) and tumour necrosis factor alpha (TNF-alpha) in bone marrow and peripheral blood CD4+ and CD8+ cells. The same cytokines were tested, by immunoassay, in culture supernatants from unstimulated bone marrow mononuclear cells (MNCs). Marrow CD4+ and CD8+ cells expressing gamma-IFN and TNF-alpha were significantly increased in the patients in comparison with normal control subjects (P from < 0.05 to < 0.0001 in the different cellular subsets). Patients' marrow CD4+ and CD8+ cells containing gamma-IFN and TNF-alpha were significantly increased when compared with the same cell fractions from paired peripheral blood samples (P from < 0.05 to < 0.0001 in the various cellular subsets). In the supernatant of marrow MNCs, gamma-IFN and TNF-alpha were detected in four out of eight and five out of eight cases, respectively, whereas neither cytokine was traceable in the control subjects. Patients' peripheral blood CD4+ and CD8+ cells containing gamma-IFN and TNF-alpha were not significantly increased in comparison with those from normal control subjects. Whereas patients with favourable and unfavourable outcomes had no significantly different proportions of marrow gamma-IFN+/CD4+ and gamma-IFN+/CD8+ cells, the percentages of marrow CD4+ and CD8+ cells containing TNF-alpha were significantly lower in subjects with favourable than in those with unfavourable outcome. Overall, these findings show that, in aplastic patients, T cells overexpressing gamma-IFN and TNF-alpha concentrate in the bone marrow and that intracytoplasmic expression of TNF-alpha in marrow CD4+ and CD8+ cells is associated with an unfavourable clinical course.