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Glucocorticoid hormones (GCH) and anti-CD3 monoclonal antibodies (MoAbs) induce in mouse thymocytes and T-cell tumor lines an active process of cell death called apoptosis. Interleukins (IL), including IL-1 and IL-2, have been reported to inhibit such apoptosis. In this study we show that IL-4 also reduced the DIMA fragmentation characteristic of dexamethasone (DEX)-induced apoptosis in thymocytes. This effect, studied in both time-course and dose-response experiments, was also detected at low IL-4 concentrations (1 U/mL) and against high DEX levels (10−7mol/L). The effect of IL-4 was blocked by an anti-IL-4 but not by an anti-IL-1a MoAb, and was thus both specific and direct. Phenotypic analysis showed that IL-4 protects predominantly CD4−CD8−and CD4+CD8−cells. Our findings suggest that intrathymic T-cell development may be influenced by IL-4.

Previous work has shown that nude (nu/nu) mice additionally immunosuppressed by splenectomy, sublethal irradiation, and treatment with antiasialo GM1 antiserum (SIA-nu/nu mice) have no detectable natural killer activity and allow the growth of human malignant lymphoblasts. We show here that all SIA-nu/nu mice engrafted intravenously with 5 × 10(6) malignant lymphoblasts originally derived from a child with a T-cell acute lymphoblastic leukemia (PF382) and from a boy with a T-cell lymphoma (ST-4) develop lethal meningeal leukemia and die within 35 days. Histologic examination of moribund SIA- nu/nu mice showed that vertebral and skull bone marrow was always replaced by proliferating human T lymphoblasts. From the spinal canal, lymphoblasts spread to the meninges, causing hind leg paralysis. Leaving the skull, they permeated the meninges and then invaded the nervous parenchyma. This efficient and reproducible experimental model may be suitable for experimental studies on the pathogenesis of meningeal leukemia.