Active suppression by T regulatory cells plays an important role in the down-regulation of T cell responses to foreign and self-Ags. Thus far, the potential role of CD4+CD25+ T cells in human tumors has not been reported. In this work we show that lung tumors contain large numbers of these cells and that they have constitutive high-level expression of CD152 (CTLA-4). Furthermore, the CD4+CD25+ T cells mediate potent inhibition of autologous T cell proliferation. Finally, regulatory T cells from patient tumors failed to inhibit the proliferation of allogeneic T cells. Together these results suggest that the CD4+CD25+ T cells found in lung tumors selectively inhibit the host immune response and therefore could contribute to the progression of lung cancer.

Chronic active hepatitis caused by infection with hepatitis B virus, a DNA virus, is a major risk factor for human hepatocellular carcinoma. Since the oncogenicity of several DNA viruses is dependent on the interaction of their viral oncoproteins with cellular tumor-suppressor gene products, we investigated the interaction between hepatitis B virus X protein (HBX)

p53 has pleiotropic functions including control of genomic plasticity and integrity. Here we report that p53 can bind to several transcription factor IIH-associated factors, including transcription-repair factors, XPD (Rad3) and XPB, as well as CSB involved in strand-specific DNA repair, via its C-terminal domain. We also found that wild-type, but not Arg273His mutant p53 inhibits XPD (Rad3) and XPB DNA helicase activities. Moreover, repair of UV-induced dimers is slower in Li-Fraumeni syndrome cells (heterozygote p53 mutant) than in normal human cells. Our findings indicate that p53 may play a direct role in modulating nucleotide excision repair pathways.

The molecular pathway of p53-dependent apoptosis (programmed cell death) is poorly understood. Because p53 binds to the basal transcription-repair complex TFIIH and modulates its DNA helicase activities, we hypothesized that TFIIH DNA helicases XPB and XPD are members of the p53-mediated apoptotic pathway. Whereas transfer of a wild-type p53 expression vector by microinjection or retroviral infection into primary normal human fibroblasts resulted in apoptosis, primary fibroblasts from individuals with xeroderma pigmentosum (XP), who are deficient in DNA repair and have germ-line mutations in the XPB or XPD gene, but not in the XPA or XPC gene, have a deficiency in the apoptotic response. This deficiency can be rescued by transferring the wild-type XPB or XPD gene into the corresponding mutant cells. XP-D lymphocytes also have a decreased apoptotic response to DNA damage by adriamycin, indicating a physiologically relevant deficiency. The XP-B or XP-D mutant cells undergo a normal apoptotic response when microinjected with the Ich-1, and ICE genes. Analyses of p53 mutants and the effects of microinjected anti-p53 antibody, Pab421, indicate that the carboxyl terminus of p53 may be required for apoptosis. Direct microinjection of the p53 carboxy-terminal-derived peptide (amino acid residues 319-3331 resulted in apoptosis of primary normal human fibroblasts. These results disclose a novel pathway of p53-induced apoptosis.

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To reduce widespread shortages, attempts are made to use more marginal livers for transplantation. Many of these grafts are discarded for fear of inferior survival rates or biliary complications. Recent advances in organ preservation have shown that ex vivo subnormothermic machine perfusion has the potential to improve preservation and recover marginal livers pre- transplantation. To determine the feasibility in human livers, we assessed the effect of 3 hours of oxygenated subnormothermic machine perfusion (21 °C) on seven livers discarded for transplantation. Biochemical and microscopic assessment revealed minimal injury sustained during perfusion. Improved oxygen uptake (1.30 [1.11–1.94] to 6.74 [4.15–8.16] mL O2/min.kg liver), lactate levels (4.04 [3.70–6.00] to 2.29 [1.20–3.42] mmol/L) and adenosine triphosphate content (45.0 [70.6–87.5] pre-perfusion to 167.5 [151.5–237.2] pmol/mg after perfusion) were observed. Liver function, reflected by urea, albumin and bile production was seen during perfusion. Bile production increased and the composition of bile (bile salts/phospholipid ratio, pH and bicarbonate concentration) became more favorable. In conclusion, ex vivo subnormothermic machine perfusion effectively maintains liver function with minimal injury and sustains or improves various hepatobiliary parameters post-ischemia.

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant diseases worldwide and has become a leading cause for cancer-related deaths in adults from Asia and sub-Saharan Africa (1). The DNA tumor virus hepatitis B virus (HBV) has been implicated to play a major causative role in the development of HCC in man (2-4). The HBx gene, the smallest viral openreading frame that may be essential for the viral life cycle (5,6), largely contributes the oncogenecity of HBV. The selective retention and expression of the HBx gene during acute and chronic hepatitis as well as in a great majority of HCCs may constitute an important step during HCC development (7,8). The oncogenic potential of the HBx gene has been experimentally demonstrated in a transgenic mice model (9) and in cell culture systems (10,11). HBx alone can induce HCC in certain transgenic mice (9) or can increase susceptibility to chemical carcinogens (12) and accelerate c-myc-induced HCC (13). Consequently, as an oncoprotein, HBx has been reported to disregulate cell-cycle transition (14,15) to potentially target certain proteases and proteasome (16-18), to interact with DNA repair factors (19,20), or to interact with the p53 tumor suppressor gene product (21-24).

Summary Regulatory B cells (Bregs) have been shown to play a critical role in immune homeostasis and in autoimmunity models. We have recently demonstrated that combined anti-TIM-1 and anti-CD45RB antibody treatment results in tolerance to full MHC-mismatched islet allografts in mice by generating Bregs that are necessary for tolerance. Bregs are antigen-specific and are capable of transferring tolerance to untreated, transplanted animals. Here we demonstrate that adoptively transferred Bregs require the presence of Tregs to establish tolerance, and that adoptive transfer of Bregs increases the number of Tregs. Interaction with Bregs in vivo induces significantly more Foxp3 expression in CD4+CD25− T cells than with naive B cells. We also show that Bregs express the TGF-β associated latency-associated peptide (LAP) and that Breg-mediated graft prolongation post-adoptive transfer is abrogated by neutralization of TGF-β activity. Regulatory B cells, like regulatory T cells, demonstrate preferential expression of both CCR6 and CXCR3. Collectively, these findings suggest that in this model of antibody-induced transplantation tolerance, Bregs promote graft survival by promoting Treg development, possibly via TGF-β production.