The transplanted liver graft is capable of clearing asymmetric dimethylarginine.

Asymmetric dimethylarginine (ADMA) has been recognized as an endogenous inhibitor of the arginine-nitric oxide (NO) pathway. Its concentration is tightly regulated by urinary excretion and degradation by the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which is highly expressed in the liver. Considering the liver as a crucial organ in the clearing of ADMA, we hypothesized increased ADMA levels during hepatic failure and, consequently, a decline of ADMA concentrations after successful liver transplantation. The aim of the present study was to investigate the role of the liver in the metabolism of ADMA in patients undergoing liver transplantation. In this prospective study, we investigated the course of ADMA concentrations in 42 patients undergoing liver transplantation and results showed that preoperative ADMA concentrations were higher in patients with acute (1.26 micromol/L, P < .001) and in patients with chronic (.69 micromol/L, P < .001) hepatic failure compared with healthy volunteers (.41 micromol/L). In addition, ADMA concentrations decreased from the preoperative day to the first postoperative day in both the acute (Delta(ADMA): -.63 micromol/L, P = .005) and the chronic hepatic failure group (Delta(ADMA): -0.15 micromol/L, P < .001). Furthermore, in patients who experienced acute rejection, ADMA concentrations were higher during the whole first postoperative month compared with nonrejectors (P = .012). Moreover, in 11 of 13 rejectors (85%) a clear increase in ADMA concentration preceded the onset of the first episode of rejection, which was confirmed by liver biopsy. In conclusion, our results indicate that the transplanted liver graft is quickly capable of clearing ADMA, suggesting preservation of DDAH. In addition, increased ADMA concentrations in the posttransplantation period reflect serious dysfunction of the liver graft during acute rejection.     

Physical fitness,fatigue, and quality of life after liver transplantation

Fatigue is often experienced after liver transplantation. The aims of this cross-sectional study were to assess physical fitness (cardiorespiratory fitness, neuromuscular fitness, body composition) in liver transplant recipients and to explore whether physical fitness is related to severity of fatigue. In addition, we explored the relationship between physical fitness and health-related quality of life. Included were 18 patients 1–5 years after transplantation (aged 48.0 ± 11.8 years) with varying severity of fatigue. Peak oxygen uptake during cycle ergometry, 6-min walk distance, isokinetic muscle strength of the knee extensors, body mass index, waist circumference, skinfold thickness, severity of fatigue, and health-related quality of life were measured. Cardiorespiratory fitness in the liver transplant recipients was on average 16–34% lower than normative values (P ≤ 0.05). Furthermore, the prevalence of obesity seemed to be higher than in the general population (17 vs. 10%). We found no deficit in neuromuscular fitness. Cardiorespiratory fitness was the only fitness component that was related with severity of fatigue (r _s = −0.61 to r _s = -0.50, P ≤ 0.05). Particularly cardiorespiratory fitness was related with several aspects of health-related quality of life (r _s = 0.48 to r _s = 0.70, P ≤ 0.05). Results of our study imply that cardiorespiratory fitness and body composition are impaired in liver transplant recipients and that fitness is related with severity of fatigue (only cardiorespiratory fitness) and quality of life (particularly cardiorespiratory fitness) in this group. These findings have implications for the development of rehabilitation programs for liver transplant recipients.     

Nuclear RNA sequences coding for alpha and beta globins in erythroid cells: evidence for multiple intermediate molecules

The poly (A)-containing nuclear RNA from dimethylsulfoxide-induced Friend leukemia cells was fractionated by acrylamide gel electrophoresis in denaturing conditions and analyzed for alpha and beta globin RNA sequences. The results indicate that nuclear RNA contains one species of large-size RNA (0.6 X 10(6) daltons), which is the putative precursor for beta globin mRNA only. In addition, it was shown by electrophoretic analysis that the complex of RNA molecules not resolved by sucrose gradient centrifugation (11S) comprises sequences of decreasing size (0.34, 0.28, and 0.26 X 10(6) daltons), which might be the precursors of alpha and beta globin mRNA.     

The FLK2/FLT3 ligand synergizes with interleukin-7 in promoting stromal- cell-independent expansion and differentiation of human fetal pro-B cells in vitro

The effects of a novel cytokine FLK2/FLT3 ligand (FL) on human fetal bone marrow-derived CD34+CD19+ pro-B cells were analyzed in a stromal- cell-independent, serum-deprived culture system. FL, like interleukin-3 (IL-3), synergized with IL-7 in promoting pro-B cell growth, and differentiation of these cells into CD34-CD19+clgM+slgM- pre-B cells, whereas a small proportion of these cells even differentiate into more mature slgM+ B cells. In contrast, KIT ligand (KL) and granulocyte- macrophage colony-stimulating factor (GM-CSF) were ineffective in promoting IL-7-dependent pro-B cell growth and differentiation. Maximal levels of pro-B cell expansion, generally resulting in 15- to 30-fold increases in cellularity, were obtained in cultures supplemented with optimal doses of FL + IL-7 + IL-3. The addition of mouse bone marrow stromal cells further enhanced the proliferation and differentiation of pro-B cells obtained in the presence of these three cytokines. Under these conditions, cultures could be maintained for more than 4 weeks, and in general 40- to 50-fold increases in cell numbers were observed by 3 weeks of culture. The percentages of clgM+ and slgM+ B cells increased 1.5- to 3-fold and 2-fold, respectively, suggesting that stromal cells may provide additional costimulatory signals for human B- cell growth and differentiation that are different from IL-7, IL-3, and FL. Collectively, our results indicate that FL, in contrast to KL, strongly promotes long-term expansion and differentiation of human pro- B cells in the presence of IL-7 or in combination of IL-7 and IL-3, which is a novel property of this hematopoietic growth factor.     

Follicular T helper cells and humoral reactivity in kidney transplant patients

Memory B cells play a pivotal role in alloreactivity in kidney transplantation. Follicular T helper (Tfh) cells play an important role in the differentiation of B cells into immunoglobulin-producing plasmablasts [through interleukin (IL)-21]. It is unclear to what extent this T cell subset regulates humoral alloreactivity in kidney transplant patients, therefore we investigated the absolute numbers and function of peripheral Tfh cells (CD4^POSCXCR5^POS T cells) in patients before and after transplantation. In addition, we studied their relationship with the presence of donor-specific anti-human leucocyte antigen (HLA) antibodies (DSA), and the presence of Tfh cells in rejection biopsies. After transplantation peripheral Tfh cell numbers remained stable, while their IL-21-producing capacity decreased under immunosuppression. When isolated after transplantation, peripheral Tfh cells still had the capacity to induce B cell differentiation and immunoglobulin production, which could be inhibited by an IL-21-receptor-antagonist. After transplantation the quantity of Tfh cells was the highest in patients with pre-existent DSA. In kidney biopsies taken during rejection, Tfh cells co-localized with B cells and immunoglobulins in follicular-like structures. Our data on Tfh cells in kidney transplantation demonstrate that Tfh cells may mediate humoral alloreactivity, which is also seen in the immunosuppressed milieu.