Joachim Riggert

Chemoattraction of Macrophages, T Lymphocytes, and Mast Cells Is Evolutionarily Conserved within the Human α-Defensin Family

Human defensins are natural peptide antibiotics. On the basis of the position and bonding of six conserved cysteine residues, they are divided into two families, designated α- and β-defensins. Human α-defensins are expressed predominantly in neutrophils (human neutrophil peptides (HNP) 1–4) or intestinal Paneth cells (human defensins (HD) 5 and 6). Although α-defensins have been implicated in the pathogenesis of inflammatory bowel disease, their immunomodulatory functions are poorly understood. In the present study, HNP-1, HNP-3, and HD5 were found to be potent chemotaxins for macrophages but not dendritic cells using Gαi proteins and MAPK as signal transducers. α-Defensins were also chemoattractive for the human mast cell line HMC-1 but lacked, in contrast to β-defensins, the ability to induce intracellular calcium fluxes. Furthermore, HNP-1, HNP-3, and HD5 comparably mobilized naive as well as memory T lymphocytes. Using the protein kinase C (PKC) inhibitors GF109 and Gö6976, we observed a PKC-independent functional desensitization to occur between human α-defensins, which suggests a common receptor for HNP-1, HNP-3, and HD5 on immune cells. This α-defensin receptor was subject to heterologous desensitization by the PKC activator PMA and to PKC-dependent cross-desensitization by human β-defensins. Conversely, α-defensins desensitized β-defensin-mediated migration of immune cells in a PKC-dependent manner, suggesting unique receptors for both defensin families. Taken together, our observations indicate that chemoattraction of macrophages, T lymphocytes, and mast cells represents an immunomodulatory function which is evolutionarily conserved within the human α-defensin family and tightly regulated by β-defensins.

β‐Defensins chemoattract macrophages and mast cells but not lymphocytes and dendritic cells: CCR6 is not involved

β‐Defensins are natural peptide antibiotics whose immunomodulatory functions are poorly understood. In the present study, macrophages were found to migrate to human β‐defensins (HBD)‐1 to ‐4 using Gαi proteins as well as MAPK ERK, p38 and JNK as signal transducers. In addition, mast cells responded to HBD‐1 to ‐4 with calcium fluxes as well as chemotaxis, which increased upon stimulation with IgE plus antigen or ionomycin. In contrast, human β‐defensins were unable to induce migration of memory lymphocytes and dendritic cells (DC). Similar to HBD, the murine β‐defensin (mBD)‐8 mobilized macrophages and lacked the ability to recruit memory T cells. These findings were unexpected as CCR6 on memory T cells and DC has been previously observed to be a receptor for human β‐defensins. In support of our findings, however, RBL‐2H3 as well as 300.19 cells stably expressing CCR6 proved to be unresponsive to HBD‐2 and ‐3. Intriguingly, our observation of a PKC‐independent homologous desensitization between HBD‐1 to ‐4 suggests a common receptor for HBD. In summary, chemoattraction of macrophages and mast cells is evolutionary conserved within the β‐defensin family despite a considerable sequence variation and distinct antimicrobial activities. However, CCR6 is not a functional receptor for β‐defensins.

Circulating regulatory T cells are reduced in obesity and may identify subjects at increased metabolic and cardiovascular risk.

Reduced numbers of regulatory T (Treg) cells have been observed in visceral adipose tissue of obese mice and humans. However, it is unknown whether human obesity affects circulating Treg cells and whether their number is associated with markers of systemic inflammation or glucose intolerance.

Profile of the Circulating DNA in Apparently Healthy Individuals

BACKGROUND Circulating nucleic acids (CNAs) have been shown to have diagnostic utility in human diseases. The aim of this study was to sequence and organize CNAs to document typical profiles of circulating DNA in apparently healthy individuals. METHODS Serum DNA from 51 apparently healthy humans was extracted, amplified, sequenced via pyrosequencing (454 Life Sciences/Roche Diagnostics), and categorized by (a) origin (human vs xenogeneic), (b) functionality (repeats, genes, coding or noncoding), and (c) chromosomal localization. CNA results were compared with genomic DNA controls (n = 4) that were subjected to the identical procedure. RESULTS We obtained 4.5 x 10(5) sequences (7.5 x 10(7) nucleotides), of which 87% were attributable to known database sequences. Of these sequences, 97% were genomic, and 3% were xenogeneic. CNAs and genomic DNA did not differ with respect to sequences attributable to repeats, genes, RNA, and protein-coding DNA sequences. CNA tended to have a higher proportion of short interspersed nuclear element sequences (P = 0.1), of which Alu sequences were significant (P < 0.01). CNAs had a significantly lower proportion of L1 and L2 long interspersed nuclear element sequences (P < 0.01). In addition, hepatitis B virus (HBV) genotype F sequences were found in an individual accidentally evaluated as a healthy control. CONCLUSIONS Comparison of CNAs with genomic DNA suggests that nonspecific DNA release is not the sole origin for CNAs. The CNA profiling of healthy individuals we have described, together with the detailed biometric analysis, provides the basis for future studies of patients with specific diseases. Furthermore, the detection of previously unknown HBV infection suggests the capability of this method to uncover occult infections.

Frequency and causes of refractoriness in multiply transfused patients

Abstract The use of leukocyte-depleted blood components has become the standard therapy for multiply transfused patients during the past few years, as a measure to reduce the frequency of alloimmunization and refractoriness. We assessed frequency and causes of refractoriness, defined as a repeated 24-h post-transfusion platelet count below 20 000/μl, in 145 consecutive patients who received three or more single-donor platelet concentrates during a 1-year period. Flow-cytometric detection of anti-platelet antibodies and a glycoprotein-specific ELISA were applied for the diagnosis of alloimmunization. Forty patients (27.6%) had at least one episode of refractoriness. In 25 of these 40 patients (62.5%), nonimmune factors (fever, sepsis, coagulopathy, splenomegaly) alone were the cause. In 15 refractory patients alloantibodies were detected. In seven patients (17.5%), alloimmunization alone caused an inadequate transfusion response, while in eight refractory patients (20.0%) alloimmunization and fever or sepsis were present. HLA antibodies were detected in 17 patients (11.7%); three patients (2%) had platelet-specific antibodies in addition to HLA antibodies; in two patients panreactive platelet antibodies were detectable. All 17 patients had a history of previous transfusions or pregnancy. We did not observe primary immunization in patients transfused exclusively with filtered (leukodepleted) blood products. Our data suggest that alloimmunization in patients with a negative risk history can be prevented by the exclusive use of leukodepleted blood components.

Anaphylatoxin C5a Induces Monocyte Recruitment and Differentiation into Dendritic Cells by TNF-α and Prostaglandin E2-Dependent Mechanisms

Although monocytes can be directed to develop into dendritic cells (DC) in vitro, the molecular mechanisms that induce their transformation in vivo are largely unknown. In the present study we employed an in vivo SCID mouse model to investigate the impact of two proinflammatory chemotaxins, the anaphylatoxin C5a and the chemokine macrophage inflammatory protein-1α (CCL3), on the differentiation of human monocytes and immature DC generated from monocytes in the presence of GM-CSF and IL-4. Both C5a and macrophage inflammatory protein-1α recruited human monocytes and immature DC into the peritoneal cavity of SCID mice, but only C5a induced their differentiation into phenotypically mature DC by 48 h after injection. Macrophages derived from monocytes by in vitro culture were resistant to C5a-mediated transformation in vivo. The effect of C5a was indirect, since C5a-stimulated TNF-α and PGE2 were found to be obligatory as well as sufficient to induce differentiation of monocytes. In contrast to monocytes, in vitro generated immature DC required TNF-α, but not PGE2, for their C5a-mediated maturation in vivo. C5a-transformed monocytes represented an inflammatory type of DC, as they constitutively secreted high amounts of TNF-α, but also retained the capacity to release the Th1 cytokine IL-12 p70 upon stimulation with CD40 ligand. In summary, we identified for the first time a cascade of inflammatory signals that can induce the transformation of monocytes into DC in vivo. This novel function emphasizes the important immunoregulatory role of C5a at the interface of innate and adaptive immunity.

IL-4 Down-Regulates Anaphylatoxin Receptors in Monocytes and Dendritic Cells and Impairs Anaphylatoxin-Induced Migration In Vivo

Anaphylatoxins mobilize leukocytes to the sites of inflammation. In the present study we investigated the impact of GM-CSF, IL-4, and IFN-γ on anaphylatoxin receptor expression in monocytes and dendritic cells (DC). IL-4 was identified as the strongest down-regulator of the receptors for C5a and C3a in monocytes and monocyte-derived DC (MoDC). To study the impact of IL-4 on anaphylatoxin-induced chemotaxis, an in vivo migration model was established. For this purpose, human monocytes and MoDC were injected i.v. into SCID mice that at the same time received anaphylatoxins into the peritoneal cavity. A peritoneal influx of human monocytes could be demonstrated by 4 h after injections of C5a and C3a. In line with receptor down-regulation, IL-4 treatment inhibited in vivo mobilization of human monocytes and MoDC in response to C5a and C3a. In addition to its effects on human cells, IL-4 reduced C5a receptors in murine bone marrow-derived DC and impaired recruitment of labeled bone marrow-derived DC in syngeneic BALB/c mice to i.p. injected C5a. Overall, these data suggest that inhibition of a rapid anaphylatoxin-induced mobilization of monocytes and DC to inflamed tissues represents an important anti-inflammatory activity of the Th2 cytokine IL-4.

Effects of Obesity and Weight Loss on the Functional Properties of Early Outgrowth Endothelial Progenitor Cells

OBJECTIVES The purpose of this study was to examine the impact of obesity and weight loss on the angiogenic and regenerative capacity of endothelial progenitor cells (EPCs). BACKGROUND EPCs participate in angiogenesis and tissue repair. Several cardiovascular risk factors are associated with EPC dysfunction. METHODS Early outgrowth EPCs were isolated from 49 obese (age 42 +/- 14 years; body mass index 42 +/- 7 kg/m(2)) normoglycemic participants in a professional weight reduction program and compared with those from 49 age-matched lean controls. EPC function was tested both in vitro and in vivo. RESULTS EPCs expanded from the obese possessed reduced adhesive, migratory, and angiogenic capacity, and mice treated with obese EPCs exhibited reduced EPC homing in ischemic hind limbs in vivo. EPCs from the obese subjects failed to respond to conditioned medium of lean controls or to potent angiogenic factors such as vascular endothelial growth factor. Although no differences existed between lean and obese EPCs regarding the surface expression of vascular endothelial growth factor or chemokine receptors, basal p38 mitogen-activated protein kinase (MAPK) phosphorylation was elevated in obese EPCs (3.7 +/- 2.1-fold increase; p = 0.006). These cells also showed reduced secretion of the angiogenic chemokines interleukin-8 (p = 0.047) and monocyte chemoattractant protein-1 (p = 0.012). By inhibiting p38 MAPK, we could restore chemokine levels to those of lean control EPCs and also improve the angiogenic properties of obese EPCs. Accordingly, 6-month follow-up of 26 obese persons who achieved significant weight reduction revealed normalization of p38 MAPK phosphorylation levels and improved EPC function. CONCLUSIONS Obesity is associated with a reversible functional impairment of EPCs. This involves reduced secretion of angiogenic chemokines and increased basal phosphorylation of signaling molecules, notably p38 MAPK.

Comparison of CD34+ cell numbers and colony growth before and after cryopreservation of peripheral blood progenitor and stem cell harvests: influence of prior chemotherapy

BACKGROUND: Quantitative determination of hematopoietic progenitor cells is a major issue in peripheral blood progenitor and stem cell collection and transfusion, although the extent is still an object of discussion. STUDY DESIGN AND METHODS: In 116 leukapheresis collections from 42 patients, immunophenotyping for CD34+ cells, evaluation of in vitro proliferative capacity by a colony‐forming unit‐granulocyte‐ macrophage (CFU‐GM) assay, and viability assessment by trypan blue exclusion were performed before and after storage in liquid nitrogen at ‐196 degrees C. RESULTS: Before storage, the median number of CD34+ cells was 1.46 × 10(6) (range, 0.01–54.05 × 10(6)) per kg of body weight (BW). There was no significant difference between precryopreservation and postcryopreservation numbers. The median number of CFU‐GM was 2.25 × 10(5) (range, 0.02–157.49 × 10(5)) per kg of BW before cryopreservation and significantly (p < 0.001) lower, 0.83 × 10(5) (range, 0–220.36 × 10(5)) per kg of BW, after cryopreservation. The correlation coefficient of prestorage and poststorage values was 0.92. The median ratio of poststorage and prestorage values was 42.3 percent (0–304.8%). Male patients who underwent intense chemotherapy (> 5 cycles) showed a significantly lower ratio of postcryopreservation and precryopreservation CFU‐GM values than other patients (p = 0.0047). A strong linear correlation was determined between the number of CD34+ cells per kg of BW and the number of CFU‐GM per kg of BW before and after cryopreservation. A viability below 50 percent predicted a high loss of in vitro proliferative capacity, while a viability above 50 percent did not correlate with a high ratio of CFU‐GM from after and before cryopreservation. CONCLUSION: A good correlation between the variables used for characterization of peripheral blood progenitor cells–the number of CD34+ cells and the number of CFU‐GM–was observed. Viability assessment by trypan blue exclusion does not seem to be a substitute for assays evaluating in vitro proliferative capacity.

Testing of individual blood donations for HCV RNA reduces the residual risk of transfusion-transmitted HCV infection.

BACKGROUND: To allow cost‐effective RNA testing with NAT techniques, the national authorities of several countries have planned or already introduced tests of mixed specimens, that is, plasma pools.