Cyclosporine directly causes oxidative stress and promotes Epstein-Barr virus transformation of human B cells.

BACKGROUND: We have previously shown that oxidative stress alone can promote transformation of human B cells infected with Epstein-Barr virus (EBV) in vitro, an accepted model mimicking posttransplant lymphoproliferative disorders (PTLDs). Our laboratory has investigated the direct effects of cyclosporine A (CyA) as an oxidant promoting B-cell transformation and we have proposed that CyA directly promotes B-cell transformation and that this effect can be blocked by antioxidants. METHODS: Human splenocytes were prepared by centrifugation and plating technique to provide a greater than 80% pure preparation of B cells that was used for the direct oxidative stress experiments. These cells were cocultured with CyA (500 ng/ml) and hydrogen peroxide (H(2)O(2), 0.15 mM) with or without antioxidant vitamin E (40 microM). Oxidative stress was evaluated by using a commercial lipid hydroperoxide (LPO) assay kit. In another set of three separate experiments, human B lymphocytes infected with EBV were cultured with CyA (500 ng/ml), H(2)O(2) (0.15 mM), and vitamin E (40 microM). B-Cell transformation by EBV was evaluated by counting colony number and [(3)H]-thymidine incorporation. RESULTS: At therapeutic concentrations, CyA (500 ng/mL) had an oxidative effect on human splenocytes in vitro, similar to the effect of H(2)O(2) (90 and 97% increases, respectively in LPO production over control P < 0.005), which was abrogated by the addition of vitamin E. Similarly, both CyA and H(2)O(2) promoted transformation of B cells infected with EBV(75 and 108% increases respectively in colony counts over control, P < 0.005). This effect was also blocked by vitamin E. CONCLUSIONS: Both CyA and H(2)O(2) have a direct oxidative effect on human B cells and cause promotion of EBV-induced transformation of B cells. These effects are blocked by the antioxidant vitamin E. These findings may have future therapeutic implications for PTLDs.

Lymphocyte apoptosis during early phase of Listeria infection in mice.

During the acute phase of growth of Listeria monocytogenes in spleen and lymph nodes, the infective foci consist of macrophages and neutrophils accompanied by extensive death of lymphocytes. Many of the lymphocytes die by apoptosis. The lesions are found by 48 hours after infection and can regress with time. Depending on the dose, the infected foci can be restricted to the thymus-dependent areas or can occupy the entire lymphoid tissue. The Listeria in the lesions are primarily found inside macrophages, but a few are extracellular amid cellular debris. Lymphocyte death appears to be an obligatory step in primary Listeria infection, the extent of which is controlled by the early restriction of Listeria growth by the innate cellular system.