Proportion versus absolute counts of B cell populations in the assessment of immunological profiles of kidney transplant recipients.

Immunophenotyping lymphocytes in kidney transplant recipients often raises questions as to whether proportions or absolute counts should be considered, especially for longitudinal assessment. Several studies conclude the pathophysiology of rejection based on proportions of naive and memory B cells. We compared the two analytical methods for B cells sampled from 82 clinically stable, adult kidney transplant recipients. Time post-transplant was analyzed both as a continuous variable and as tertiles (<1.5 years, 1.5-8 years, and > 8 years). B cells were stained for CD38 and IgD and were classified according to mature B cells (Bm) classification. The proportion of cells in the naive Bm2 compartment decreased by more than half in the late versus the early tertile, whereas the percentages of memory early Bm5 tripled and that of memory Bm5 cells doubled. In contrast, we observed a substantial reduction in naive B cell counts, but very stable memory B cell counts. Linear regressions showed that the absolute reduction in the Bm2 cell compartment was independent of age, sex, graft function, immunosuppression scheme, and rejection occurrence. In conclusion, the physiological reservoir of naive cells decreases over time post-transplant in kidney recipients, whereas that of memory B cells remains stable. Peripheral B subset percentages should be interpreted cautiously when analyzing pathophysiological processes.

Tacrolimus prevents von Willebrand factor secretion by allostimulated human glomerular endothelium.

Little is known about the endothelial injury caused directly by circulating donor-specific antibodies (DSAs) during antibody-mediated rejection. von Willebrand factor (vWF) is a highly thrombotic glycoprotein stored in Weibel-Palade bodies in endothelial cells. It has been shown that its secretion is triggered by allostimulation. Calcineurin-like phosphatases regulate pathways involved in vWF secretion. Therefore, we hypothesized that tacrolimus would prevent alloantibody-induced glomerular lesions, in part via inhibition of vWF secretion from endothelial cells. Here, we used a human in vitro model of glomerular endothelium expressing HLA class I and II antigens and demonstrated that anti-HLA class II antibodies elicit a higher endothelial release of vWF than do anti-HLA class I antibodies in cell supernatants. We observed that tacrolimus treatment decreased vWF secretion after stimulation with both classes of anti-HLA antibodies and decreased platelet adhesion on allostimulated endothelial cells in a microfluidic chamber. In kidney recipients, tacrolimus trough levels were negatively associated with vWF blood levels. These results indicate that direct disruption of hemostasis via vWF secretion is a potential mechanism of antibody-mediated injury in patients with DSAs. Our results further suggest that the targeting of microcirculation hemostasis may be beneficial to prevent the development of microangiopathic lesions in antibody-mediated rejection.

Effects of alloantibodies to human leukocyte antigen on endothelial expression and serum levels of thrombomodulin.

Essentials The effect of alloantibodies on the endothelial expression of thrombomodulin is unknown. Thrombomodulin was quantified in stimulated endothelial cells and measured in serum samples. Anti-human leukocyte antigen (HLA) I vs. II antibodies have different effects on thrombomodulin. Anti-HLA II antibodies may promote a prothrombotic state and contribute to microangiopathy. SUMMARY: Rationale Thrombomodulin (TBM) is an anticoagulant and anti-inflammatory transmembrane protein expressed on endothelial cells. Donor-specific alloantibodies, particularly those against human leukocyte antigen (HLA) class II, are associated with microvascular endothelial damage in solid allografts. Objective Our aim was to characterize the effects of anti-HLA antibodies on endothelial expression of TBM, and in particular, the differential effects of anti-HLA class I compared with those of anti-HLA class II. Methods We used human glomerular microvascular endothelial cells to examine TBM expression on anti-HLA-treated cells, and we tested sera from transplant recipients for soluble TBM. Results We found that whereas membrane TBM expression increased in a dose-dependent manner in the presence of anti-HLA class I antibodies, treatment with anti-HLA class II led to minimal TBM expression on the endothelial surface but to a cytosolic accumulation. Platelet adhesion studies confirmed the functional impact of anti-HLA class II. Quantitative densitometry of the membrane lysates further suggested that anti-HLA class II impairs TBM glycosylation. Furthermore, we found a significant association between the presence of circulating anti-HLA class II antibodies in transplant recipients and low serum levels of TBM. Conclusion These results indicate that ligation of anti-HLA class I and II antibodies produces different effects on the endothelial expression of TBM and on serum levels of TBM in transplant recipients. Anti-HLA class II antibodies may be associated with a prothrombotic state, which could explain the higher occurrence of microangiopathic lesions in the allograft and the poor outcomes observed in patients with these alloantibodies.

MS incidence and prevalence in Africa, Asia, Australia and New Zealand: A systematic review.

OBJECTIVES: Studies of multiple sclerosis (MS) incidence and prevalence from Africa, Asia, Australia and New Zealand are relatively scarce. We systematically reviewed MS incidence and prevalence in these regions including a standardized evaluation of study quality. METHODS: We searched MEDLINE and EMBASE databases for studies of MS prevalence or incidence in Africa, Asia, Australia and New Zealand published in English or French between January 1, 1985 and January 31, 2011. Study quality was assessed using a standardized tool. All steps of the review were performed in duplicate. RESULTS: Of 3925 citations identified, 28 studies met inclusion criteria and 21 of these were from Asia. Quality scores ranged from 1/8 to 8/8; the lowest scores were observed in studies from Asia (median 4/8, IQR 3,6). Prevalence was lowest in South African Blacks (0.22/100,000) and highest amongst Australian-born individuals in Australia (125/100,000). Prevalence increased over time in many countries. MS prevalence increased with increasing latitude only in some regions, and prevalence varied significantly with ethnicity. Eight studies reported incidence, which ranged from 0.67/100,000/year in Taiwan to 3.67/100,00/year in Australia. CONCLUSIONS: This comprehensive study provides an update of MS epidemiology in Africa, Asia, Australia, and New Zealand. Incidence and prevalence were lowest in Africa and Asia and highest in Australia, but many Asian studies were of poor quality. Use of consistent case ascertainment methods, standardized data collection tools, and similar outcomes would all improve study quality and comparability. The underlying basis of observed ethnic differences is an important area for future study.

Aplastic crisis associated with parvovirus B19 in an adult with hereditary spherocytosis.

Parvovirus B19 is usually associated with an acute, self-limited disease in children. In patients with a congenital hemolytic anemia, infection with this virus can cause an aplastic crisis. We describe such a crisis in an adult with asymptomatic hereditary spherocytosis. The association between acute red blood cell aplasia and infection with parvovirus B19 is well described in patients with hereditary hemolytic anemia, particularly sickle cell anemia. This association has also been described, although less frequently, in patients with other inherited hemolytic diseases, such as hereditary spherocytosis. In children, human parvovirus B19 causes an acute self-limited illness known as erythema infectiosum (fifth disease). In immunocompromised individuals, chronic infections can occur and cause a severe, persistent anemia. In pregnant women, infection can, but usually does not, lead to fetal infection. An infected fetus can have severe anemia, congestive heart failure, generalized edema (fetal hydrops) and even death. Most cases of aplastic crises associated with parvovirus B19 in patients with hereditary spherocytosis have been reported in children and adolescents. In this paper we describe an aplastic crisis in a 28 year old man with asymptomatic hereditary spherocytosis.

Localization of adrenal and extra-adrenal pheochromocytomas by magnetic resonance imaging.

We found magnetic resonance imaging helpful in the localization of both an adrenal and an extra-adrenal pheochromocytoma, since these tumors produced a high-intensity "light bulb" image. MRI is an excellent method for localizing pheochromocytomas because it detects adrenal and extra-adrenal pheochromocytomas missed by computerized tomography and adrenal-renal ultrasonography, and because the high-intensity MRI signal generated by pheochromocytomas is useful in differentiating them from nonfunctioning adrenal masses in hypertensive patients.

Mechanisms of transport of L-histidine and beta-alanine in hamster small intestine.

Whole rings of hamster jejunum and ileum were used to study the uptake of L-histidine (L-His) and beta-alanine (beta-Ala), the constituents of the dipeptide carnosine. The rate of uptake of L-His and beta-Ala (1 mM) was not significantly different in the jejunum compared with the ileum. Results of total influx (2 min) of 0.5-100 mM L-His suggested that transport was by more than one pathway, and the contribution of nonmediated component was calculated to be 0.24 mumol X g-1 X 2 min-1 X mM-1 for both jejunum and ileum. The apparent affinity of L-His for a transporter was higher in the ileum (K iota, 8.0 mM) than the jejunum (Kt, 11.7 mM). Influx (2 min) of beta-Ala was found to be linearly related to substrate concentration over the range 0.5-100 mM. The Kd (rate constant for nonmediated uptake of beta-Ala) was 0.23 and 0.14 mumol X g-1 X 2 min-1 X mM-1 for jejunum and ileum, respectively. Steady-state (20-min) uptake of L-His was significantly higher in the ileum than jejunum at substrate concentrations of 75 mM. L-His accumulated in the tissue up to a medium concentration of 50 mM in the jejunum and 75 mM in the ileum. In contrast, no evidence of tissue accumulation of beta-Ala was found in 20-min incubations. beta-Ala steady-state uptake in the ileum was significantly higher than in the jejunum at substrate concentrations of 30 and 75 mM.

Infective endocarditis due to Leptotrichia buccalis: a case report.

A patient with Down's syndrome presented with infective endocarditis due to Leptotrichia buccalis. The source of the infection was not detected, but the predisposing factor was a complex cardiac malformation. The disease followed a subacute course, had a number of immunologic manifestations and was successfully treated with a 28-day course of penicillin G, given intravenously. L. buccalis has never been reported before as a cause of endocarditis.

Effect of biological time on the determination of the LD50 of 5-fluorouracil in mice.

The LD50 was determined for 5-fluorouracil (FU) in mice at 11.00 and 23.00 h during one 24-hour period. These times were chosen because in mice kept on a light-dark cycle, with lights on from 06.00 to 18.00 h, the natural circadian rhythm in DNA synthetic activity in many different normal organs attains peak levels around 24.00 h (mid-dark) and through levels around 12.00 h (mid-light). The LD50 of FU, in milligrams per kilogram body weight, was much higher (450-500 mg/kg) at 11.00 than at 23.00 h (250-300 mg/kg). Since the biology of the living animal oscillates significantly on a daily or circadian basis, it is understandable that the degree of susceptibility or resistance to drugs should also fluctuate over the circadian period. Determination of the LD50 of a drug at that point in time when the animal is naturally resistant to that drug will result is a false appraisal of the toxic effects to the drug. To assess correctly the risk a drug poses, it should be tested at its time of maximal susceptibility in the living animal.

Induction by 5-fluorouracil of a major phase difference in the circadian profiles of DNA synthesis between the Ehrlich ascites carcinoma and five normal organs.

DNA synthetic activity (DNA-SA) was measured by the incorporation of tritiated thymidine (TDR) into chemically isolated DNA. DNA-SA was monitored every 3 h over a 60-h period in the Ehrlich ascites carcinoma (EAC), tongue, bone marrow, ileum, stomach and rectum in mice which had received 50 mg/kg 5-fluorouracil (FU) at 17:00 h. FU was given in an attempt to induce major phase differences in the circadian profiles of DNA-SA between the EAC and the normal organs. Subsequent to the FU treatment, a time period 15 h in duration, was identified when DNA-SA in the EAC was at or near a maximal level (125-190 cpm/micrograms DNA) whereas DNA-SA in all 5 normal organs was at or near a minimal level (less than 60 cpm/micrograms DNA). Induction of such quantitative (actual levels of DNA-SA) and qualitative (180 degrees circadian phase change) differences between the normal and neoplastic cells in the same host should be useful in designing a more effective chemotherapeutic protocol for this tumor-host situation.