Previous studies have demonstrated that peripheral blood mononuclear cells (BMC) from type 1 (insulin-dependent) diabetic patients inhibit insulin release (IR) from rat or mouse islet cells in vitro. This phenomenon is of great interest as a model for islet graft rejection. We found that lipopolysaccharide (LPS)-stimulated BMC of healthy donors and type 1 diabetic patients suppress both basal and stimulated insulin secretion. To study whether this inhibition was due to soluble mediators we added supernatants of LPS-stimulated BMC or recombinant human interleukin-1 beta (IL-1) and tumor necrosis factor-alpha (TNF) at concentrations comparable to those found in the supernatants to rat islet cells. The inhibitory effect of BMC on islet cells could be transferred by supernatants of LPS-stimulated BMC. We found that neither IL-1 nor TNF alone inhibit IR from dispersed adult rat islet cells. However, the combination of IL-1 and TNF was highly effective. Ultrafiltration of supernatants of LPS-stimulated BMC through a PM-10 membrane (10 kDa cutoff) deprived the supernatants of the inhibitory activity indicating that only intact IL-1 and TNF (m.w. about 17 kDa), but not smaller IL-1 and TNF fragments, were responsible for the effects on islet cells. These data suggest that activation of BMC and cytokine release at islet graft site may result in an early loss of graft function. Islet transplantation using microcapsules not permeable for molecules with m.w. > 10 kDa would be preferable.

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The present study demonstrates that with time in culture blood monocytes (MO) lose their ability to express procoagulant activity (PCA) and secrete tumor necrosis factor-alpha (TNF alpha) in culture medium in response to lipopolysaccharide (LPS) stimulation. Thus, upon 10 micrograms/ml LPS stimulation for 4 hours 2-day-old MO produced lower levels of PCA and TNF alpha than fresh MO. The decrease in responsiveness was not caused by cell death, since in the case of TNF alpha it was fully reversible by interferon-gamma (IFN-gamma). Compared with cells pre-incubated in medium alone, the responsiveness of MO pre-incubated in LPS was further decreased. Thus, in MO LPS pre-incubation was followed by an LPS refractory state. It was expected that the decrease in responsiveness induced by cultivation in medium alone was mediated by LPS contamination of culture medium. However, as we were unable to prevent this decrease by neutralizing LPS contamination of the culture medium with polymyxin B, the loss in LPS-induced activities of cultured MO is likely to be mediated by culture conditions other than LPS contamination. Taken together the present data demonstrate that LPS-dependent as well as LPS-independent pathways of MO desensitization to LPS exist.

Treatment of chronic hepatitis B in renal transplant recipients remains one of the major problems in clinical nephrology. Lamivudine is considered to be a drug of choice for these patients, however, its efficacy in patients with hepatitis B after renal transplantation (RT) has not been completely proven. Twenty-two RT recipients treated with lamivudine were evaluated. The duration of treatment was 15.6±1.9 months. Fourteen patients (64%) had normalization of aminotransferase (ALT); in 9 of them (41% of the whole group), serum HBV DNA was eliminated. Serum HBeAg was undetectable in 4 out of 15 (27%) previously positive patients. It has been statistically proven that the efficacy of lamivudine therapy correlates with degree of fibrosis and higher histological activity index values. We could not establish any correlation between the outcome of antiviral therapy and patients' age, sex, conditions of contagion (while on dialysis or after RT), time lapsed after the infection had been detected, duration of post-transplant period, type of immunosuppression, HBeAg positivity or negativity, ALT levels, concomitant HCV infection. The efficacy of antiviral HBV therapy is limited by the duration of lamivudine treatment: in 4 out of 5 patients with virologic response, the viremia condition relapsed several weeks after the medication had been stopped. Two patients continued to sustain their biochemical response and 1 patient had ALT levels elevated to above normal, but the value was almost twice as low as initially reported. Liver biopsy was repeated in 4 RT recipients after the end of antiviral therapy; in 3 of them positive morphologic changes were observed.

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