Th2 and Th9 responses in patients with chronic mucocutaneous candidiasis and hyper-IgE syndrome.

BACKGROUND: STAT1 mutations cause chronic mucocutaneous candidiasis (CMC), while STAT3 mutations cause hyper-IgE syndrome (HIES). CMC and HIES patients have T helper (Th) 17 defects suffering from mucosal Candida infections, but only patients with HIES show an allergic phenotype with eczema, eosinophilia and high IgE levels. OBJECTIVE: We investigated whether differential Th2 and Th9 responses may explain the clinical differences. METHODS: Peripheral blood mononuclear cells of patients with CMC (n = 4), patients with HIES (n = 4), patients with atopic dermatitis (n = 4) and healthy volunteers (n = 13) were stimulated with Candida and Staphylococcus aureus, with and without IL-4. The cytokines IL-5, IL-13, IL-9, IL-17 and TGFß and regulatory T cells were measured in cell culture supernatants by ELISA or flow cytometry, respectively. RESULTS: Peripheral blood mononuclear cells of patients with CMC showed a significantly impaired production of the Th2 cytokines IL-5 and IL-13, especially in the presence of IL-4. Moreover, IL-9 production was significantly lower in patients with CMC compared to healthy controls. In contrast, patients with HIES and patients with AD showed normal IL-5 and IL-13 production, while IL-9 production was significantly lower in patients with HIES compared to healthy controls. Although TGFß was involved in the IL-4-induced IL-9 production, TGFß levels and the frequency of regulatory T cells did not differ between patients with HIES and controls. Flow cytometry analysis demonstrated an IL-9+ IL-17+ CD4+ subset in healthy controls after stimulation with Candida which was less present in patients with HIES. CONCLUSION: Patients with CMC have a general Th defect including Th2 and Th9, while patients with HIES have normal Th2 cytokines. These differences are in line with their clinical presentation. Surprisingly, the allergic cytokine IL-9 was deficient in both HIES and CMC, suggesting a Th-17-derived origin.

Pattern recognition pathways leading to a Th2 cytokine bias in allergic bronchopulmonary aspergillosis patients.

BACKGROUND: Allergic bronchopulmonary aspergillosis (ABPA) is characterised by an exaggerated Th2 response to Aspergillus fumigatus, but the immunological pathways responsible for this effect are unknown. OBJECTIVE: The aim of this study was to decipher the pattern recognition receptors (PRRs) and cytokines involved in the Aspergillus-specific Th2 response and to study Aspergillus-induced responses in healthy controls and ABPA patients. METHODS: Peripheral blood mononuclear cells (PBMCs) were stimulated with heat-killed Aspergillus conidia, various other pathogens, or PRR ligands. PRRs and cytokine pathways were blocked with PRR-blocking reagents, anti-TNF (Etanercept or Adalimumab), IL-1Ra (Anakinra) or IFNγ (IFN-gamma). ELISA and FACS were used to analyse cytokine responses. RESULTS: Aspergillus was the only pathogen that stimulated the Th2 cytokines IL-5 and IL-13, while Gram-negative bacteria, Gram-positive bacteria, Candida albicans, chitin, ß-glucan or Toll-like receptor (TLR) ligands did not. Depletion of CD4(+) cells abolished IL-13 production. Blocking complement receptor 3 (CR3) significantly reduced IL-5 and IL-13, while blocking TLR2, TLR4 or dectin-1 had no effect. ABPA patients displayed increased Aspergillus-induced IL-5 and IL-13 and decreased IFNγ production compared with healthy controls. All biological agents tested showed the capability to inhibit Th2 responses, but also decreased Aspergillus-induced IFNγ. CONCLUSIONS AND CLINICAL RELEVANCE: Aspergillus conidia are unique in triggering Th2 responses in human PBMCs, through a CR3-dependent pathway. ABPA patients display a significantly increased Aspergillus-induced Th2/Th1 ratio that can be modulated by biologicals. These data provide a rationale to explore IFNγ therapy in ABPA as a corticosteroid-sparing treatment option, by dampening Th2 responses and supplementing the IFNγ deficiency at the same time.

Functions of microtubules in the Saccharomyces cerevisiae cell cycle.

We used the inhibitor nocodazole in conjunction with immunofluorescence and electron microscopy to investigate microtubule function in the yeast cell cycle. Under appropriate conditions, this drug produced a rapid and essentially complete disassembly of cytoplasmic and intranuclear microtubules, accompanied by a rapid and essentially complete block of cellular and nuclear division. These effects were similar to, but more profound than, the effects of the related drug methyl benzimidazole carbamate (MBC). In the nocodazole-treated cells, the selection of nonrandom budding sites, the formation of chitin rings and rings of 10-nm filaments at those sites, bud emergence, differential bud enlargement, and apical bud growth appeared to proceed normally, and the intracellular distribution of actin was not detectably perturbed. Thus, the cytoplasmic microtubules are apparently not essential for the establishment of cell polarity and the localization of cell-surface growth. In contrast, nocodazole profoundly affected the behavior of the nucleus. Although spindle-pole bodies (SPBs) could duplicate in the absence of microtubules, SPB separation was blocked. Moreover, complete spindles present at the beginning of drug treatment appeared to collapse, drawing the opposed SPBs and associated nuclear envelope close together. Nuclei did not migrate to the mother-bud necks in nocodazole-treated cells, although nuclei that had reached the necks before drug treatment remained there. Moreover, the double SPBs in arrested cells were often not oriented toward the budding sites, in contrast to the situation in normal cells. Thus, microtubules (cytoplasmic, intranuclear, or both) appear to be necessary for the migration and proper orientation of the nucleus, as well as for SPB separation, spindle function, and nuclear division.

A systems genomics approach identifies SIGLEC15 as a susceptibility factor in recurrent vulvovaginal candidiasis.

Candida vaginitis is a frequent clinical diagnosis with up to 8% of women experiencing recurrent vulvovaginal candidiasis (RVVC) globally. RVVC is characterized by at least three episodes per year. Most patients with RVVC lack known risk factors, suggesting a role for genetic risk factors in this condition. Through integration of genomic approaches and immunological studies in two independent cohorts of patients with RVVC and healthy individuals, we identified genes and cellular processes that contribute to the pathogenesis of RVVC, including cellular morphogenesis and metabolism, and cellular adhesion. We further identified SIGLEC15, a lectin expressed by various immune cells that binds sialic acid-containing structures, as a candidate gene involved in RVVC susceptibility. Candida stimulation induced SIGLEC15 expression in human peripheral blood mononuclear cells (PBMCs) and a polymorphism in the SIGLEC15 gene that was associated with RVVC in the patient cohorts led to an altered cytokine profile after PBMC stimulation. The same polymorphism led to an increase in IL1B and NLRP3 expression after Candida stimulation in HeLa cells in vitro. Last, Siglec15 expression was induced by Candida at the vaginal surface of mice, where in vivo silencing of Siglec15 led to an increase in the fungal burden. Siglec15 silencing was additionally accompanied by an increase in polymorphonuclear leukocytes during the course of infection. Identification of these pathways and cellular processes contributes to a better understanding of RVVC and may open new therapeutic avenues.

[Aspiration of water during underwater birth]. / Wateraspiratie door neonaat tijdens badbevalling.

BACKGROUND: Underwater birth is becoming increasingly popular because of the advantages for the mother. Women who deliver in this way feel less pain and therefore pain relief is less frequently needed during the delivery. But what seems to be forgotten is the fact that aspiration of water by the neonate could take place during an underwater birth, resulting in respiratory distress. CASE DESCRIPTION: A one-day-old neonate was admitted because of tachypnoea following underwater delivery at home. The respiratory rate of the neonate was one hundred breaths per minute without evident signs of dyspnoea. Chest radiography showed bilateral patches on the lungs consistent with aspiration of bathwater. After seven days of intravenous antibiotic treatment, the neonate recovered and could be discharged home. CONCLUSION: An underwater birth may cause respiratory problems in the neonate. If a pregnant woman wants to deliver under water, she should also be advised of the potential detrimental consequences for the neonate.

Allostimulatory Effects of Dendritic Cells with Characteristic Features of a Regulatory Phenotype.

INTRODUCTION: Tolerogenic dendritic cells (DCs) have the potential to prolong graft survival after transplantation. Tolerogenic DCs are in general characterized by a low expression of co-stimulatory molecule and a high IL-10:IL-12 production ratio. Based on promising results with earlier used alternatively activated DCs, we aimed to generate in culture potentially tolerogenic DC by simultaneously blocking GSK3 by lithium chloride (LiCl) and stimulating TLR2 by PAM3CysSerLys4. MATERIALS AND METHODS: Bone marrow-derived LiClPAM3 DCs were generated by the addition of LiCl 24 hours before harvesting, and one hour later PAM3CysSerLys4. The phenotype of the DCs was assessed by determining the expression of co-stimulatory molecules in flow cytometry and cytokine production in ELISA, whereas their functional properties were tested in a mixed lymphocyte reaction. A fully MHC mismatched heterotopic heart transplant preceded by infusion of donor-derived LiClPAM3 DC was performed to assess the tolerogenic potential of LiClPAM3 DCs in vivo. RESULTS: LiClPAM3 DCs displayed a tolerogenic phenotype accompanied with a low expression of co-stimulatory molecules and a high IL-10:IL-12 production ratio. However, in mixed lymphocyte reaction, LiClPAM3 DCs appeared superior in T cell stimulation, and induced Th1 and Th17 differentiation. Moreover, mice pretreated with LiClPAM3 DC displayed a reduced graft survival. Analysis of LiClPAM3 DC culture supernatant revealed high levels of CXCL-1, which was also found in supernatants of co-cultures of LiClPAM3 DC and T cells. Nevertheless, we could not show a role for CXCL-1 in T cell proliferation or activation in vitro. DISCUSSION: LiClPAM3 DCs display in vitro a tolerogenic phenotype with a high IL-10:IL-12 ratio, but appeared to be highly immunogenic, since allograft rejection was accelerated. As yet unidentified LiClPAM3 DC-derived factors, may explain the immunogenic character of LiClPAM3 DCs in vivo.

Aspergillus Cell Wall Chitin Induces Anti- and Proinflammatory Cytokines in Human PBMCs via the Fc-γ Receptor/Syk/PI3K Pathway.

UNLABELLED: Chitin is an important cell wall component of Aspergillus fumigatus conidia, of which hundreds are inhaled on a daily basis. Previous studies have shown that chitin has both anti- and proinflammatory properties; however the exact mechanisms determining the inflammatory signature of chitin are poorly understood, especially in human immune cells. Human peripheral blood mononuclear cells were isolated from healthy volunteers and stimulated with chitin from Aspergillus fumigatus Transcription and production of the proinflammatory cytokine interleukin-1ß (IL-1ß) and the anti-inflammatory cytokine IL-1 receptor antagonist (IL-1Ra) were measured from the cell culture supernatant by quantitative PCR (qPCR) or enzyme-linked immunosorbent assay (ELISA), respectively. Chitin induced an anti-inflammatory signature characterized by the production of IL-1Ra in the presence of human serum, which was abrogated in immunoglobulin-depleted serum. Fc-γ-receptor-dependent recognition and phagocytosis of IgG-opsonized chitin was identified as a novel IL-1Ra-inducing mechanism by chitin. IL-1Ra production induced by chitin was dependent on Syk kinase and phosphatidylinositol 3-kinase (PI3K) activation. In contrast, costimulation of chitin with the pattern recognition receptor (PRR) ligands lipopolysaccharide, Pam3Cys, or muramyl dipeptide, but not ß-glucan, had synergistic effects on the induction of proinflammatory cytokines by human peripheral blood mononuclear cells (PBMCs). In conclusion, chitin can have both pro- and anti-inflammatory properties, depending on the presence of pathogen-associated molecular patterns and immunoglobulins, thus explaining the various inflammatory signatures reported for chitin. IMPORTANCE: Invasive aspergillosis and allergic aspergillosis are increasing health care problems. Patients get infected by inhalation of the airborne spores of Aspergillus fumigatus A profound knowledge of how Aspergillus and its cell wall components are recognized by the host cell and which type of immune response it induces is necessary to develop target-specific treatment options with less severe side effects than the treatment options to date. There is controversy in the literature about the receptor for chitin in human cells. We identified the Fc-γ receptor and Syk/PI3K pathway via which chitin can induce anti-inflammatory immune responses by inducing IL-1 receptor antagonist in the presence of human immunoglobulins but also proinflammatory responses in the presence of bacterial components. This explains why Aspergillus does not induce strong inflammation just by inhalation and rather fulfills an immune-dampening function. While in a lung coinfected with bacteria, Aspergillus augments immune responses by shifting toward a proinflammatory reaction.

Detergent-induced specificity of an antirhodopsin serum for opsin. Micro-complement fixation studies.

An antiserum elicited in rabbit against dark-adapted rod outer segment membranes has been characterized by means of the micro-complement fixation technique. Both particulate rhodopsin and opsin, either biochemically intact or denatured and either membrane-bound or in the absence of lipids, are able to interact with the antiserum. Solubilization of the antigens in increasing concentrations of Emulphogene BC-720 leads to complete loss of complement fixation with both rhodopsin and opsin, but in the case of opsin this requires almost 10-times more detergent. In the case of opsin this masking phenomenon is preceded by a drastic exposure of antigenic sites which in the membrane vesicles are not accessible to the antibodies. Absorption experiments show that the antigenic sites on membrane-bound rhodopsin and opsin, as well as on Emulphogene BC-720-solubilized opsin, are of the same nature. Competition experiments show that the masking effect of the detergent is due to an inhibition of the primary antigen-antibody interaction and not to the inhibition of lattice formation. The use of detergents other than Emulphogene BC-720 further demonstrates that detergents more efficiently mask the antigenicity of conformationally intact than of denatured rhodopsinoids. The balance between the masking and the denaturing efficiency of a particular detergent determines whether a detergent-induced immunological discrimination can be observed between rhodopsin and opsin. The detergent-induced masking effects described are typical for the present antiserum and are probably dependent on methodological details of the immunization procedure.

Monocytes/macrophages rather than PMN are involved in early cartilage degradation in cationic immune complex arthritis in mice.

We investigated the involvement of polymorphonuclear granulocytes (PMN) and monocytes in cartilage degradation in immune complex-mediated arthritis (ICA). ICA induced with lysozyme-antilysozyme in the murine knee joint is characterized by a major influx of PMNs followed by monocytes and marked cartilage proteoglycan (PG) depletion develops within 2 days. Around 60% of 35S-prelabeled PG is lost at day 2. Influx of cells was manipulated using interleukin-1 (IL-1) receptor antagonist (IL-1ra) or antibodies to adhesion molecules. Cellular infiltrate was analyzed on hematoxylin-stained joint sections. Early systemic treatment with IL-1ra highly reduced PMN influx, whereas monocyte influx was hardly diminished. PG loss was not significantly reduced, declining from 62% in controls to 47% in IL-1ra-treated mice. Total blockade of cell influx was found after intravenous treatment with monoclonal antibodies 5C6 (anti-CD11b/CD18:anti-CR3) or NIMP.R14 (25-30 kDa protein mainly present on PMN) and PG loss was reduced to 5-10%. A similar reduction was observed after prior depletion of circulating PMNs with total body irradiation. Because amounts of IL-1 produced in leukopenic and control arthritic joints are comparable, this suggests that IL-1 is only marginally involved in PG loss in the first phase of ICA. This study indicates that monocytes rather than PMN might be involved in PG loss in this form of arthritis, either directly or by local activation of synovial layer cells of the joint.

Isolation and sequence analysis of CDC43, a gene involved in the control of cell polarity in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae CDC43 gene product is involved in establishing cell polarity during the cell-division cycle. When grown at restrictive temperatures, temperature-sensitive cdc43 mutants are unable to form buds and display delocalized cell-surface deposition [Adams et al., J. Cell Biol. (1990) in press]. We have isolated a cdc43-complementing plasmid from a yeast genomic-DNA library and localized the CDC43 gene, by subcloning and transposon-mutagenesis experiments, to a 1.2-kb region of DNA that contained only one significant ATG-initiated open reading frame of 213 codons. The putative CDC43 gene product contains a possible nuclear-localization signal sequence, a cysteine-rich domain and a histidine-rich domain, and a region that is similar in structure to alpha-helix-turn-alpha-helix structural domains present in some prokaryotic and eukaryotic DNA-binding proteins.

An assay for the quantitative measurement of in vitro phagocytosis of early apoptotic thymocytes by murine resident peritoneal macrophages.

Research into the mechanisms by which apoptotic cells are phagocytosed has grown considerably over recent years, together with a growing appreciation of the importance of clearance of redundant cells for tissue homeostasis. However, studies addressing the efficacy of phagocytosis have been rare. The few studies reported to date were either attempts to determine apoptotic cell clearance from the circulation or were focused on clearance in inflammation. We now describe an in vitro assay which permits the quantitative measurement of phagocytosis of apoptotic cells by murine resident peritoneal macrophages. The apoptotic cells used in the assay were murine thymocytes incubated with dexamethasone for only 3 h. Most apoptotic thymocytes were annexin V positive and propidium iodide negative and therefore still in the earlier stages of apoptosis. The assay was completed 7 h after the isolation of both macrophages and thymocytes, while macrophage culture time was only 4 h. Because of this short-term culture it is likely that the resident peritoneal macrophages largely maintained their in vivo phenotype. Using BALB/c macrophages and thymocytes, the maximal in vitro phagocytosis exceeded five thymocytes per macrophage in 1 h and two of these thymocytes were taken up within 10 min. Therefore, in vitro phagocytosis by resident peritoneal macrophages was rapid and of high capacity, as it is postulated to be in vivo. Under selected conditions, the mean uptake was 4.45+/-0.70 (mean +/- SD, n = 31) thymocytes per macrophage in 1 h. The inter-assay coefficient of variation, also representing the biological variability, was found to be 15.7%. The average intra-assay coefficient of variation was 13.6%. This assay permits comparisons of phagocytic efficacy between different strains of mice in vitro. In addition, a method of preparation is described which allows long-term storage of experimental results. Finally, our data suggests that internalization, but not binding of apoptotic cells to short-term cultured resident peritoneal macrophages, is critically dependent on the presence of serum. This allows separate analysis of binding and internalization of apoptotic cells with the assay, without the necessity to use agents blocking internalization.

Role of polymorphic Fc receptor Fc gammaRIIa in cytokine release and adverse effects of murine IgG1 anti-CD3/T cell receptor antibody (WT31).

Anti-CD3 monoclonal antibody (mAb) OKT3 is immunosuppressive, but causes severe adverse effects during the first administration ("first-dose reaction"). These adverse effects are presumably caused by cytokine release that results from T-cell activation. In vitro, T-cell activation by anti-CD3 mAb requires interaction with monocyte Fc receptors. The Fc receptor for murine IgG1, Fc gammaRIIa, is polymorphic. In some individuals, murine IgG1 anti-CD3 mAb causes T-cell proliferation and cytokine release in vitro (high responders [HR]), whereas in individuals with the low-responder (LR) phenotype it does not. We have now investigated the role of this Fc gammaRIIa polymorphism in the release of cytokines in vivo and the occurrence of adverse effects after the administration of WT31, a murine IgG1 anti-CD3/T cell receptor mAb. WT31 caused an increase of plasma tumor necrosis factor-alpha in all four HR patients and none of the five LR patients. In all HR patients except one, plasma gamma-interferon and interleukin 6 also increased, and a first-dose response was observed, whereas no cytokine release or adverse effects occurred in any of the LR patients. WT31 caused lymphopenia in all HR and none of the LR patients. FACS analysis demonstrated that in HR patients, after the initial disappearance of CD3+ cells from peripheral blood, modulation of CD3 occurred, whereas in LR patients a high degree of coating of the lymphocytes was observed. Surprisingly, WT31 also induced a marked granulocytopenia, as well as a decrease of thrombocytes, in three of the four HR patients (and in none of the LR patients). These data provide direct clinical evidence that Fc receptor interaction determines the release of cytokines and the occurrence of adverse effects after administration of anti-CD3/T cell receptor mAb. Furthermore, these data suggest that tumor necrosis factor-alpha by itself is not sufficient to induce the first-dose reaction.

Both early and late apoptotic blebs are taken up by DC and induce IL-6 production.

During apo blebs, containing nuclear components, are formed at the cells' surfaces. When these blebs separate from the dying cell an apo cell body remains. The contents of apo blebs are modified and can be released, especially in patients with systemic lupus erythematosus (SLE) since impaired clearance of apo material has been observed in this autoimmune condition. Accordingly, autoantibodies present in subjects with SLE bind to apo blebs. Based on AnxA5 binding, and permeability for PI, we show that apo blebs can be categorized as early (AnxA5(+)/PI(- )) or late (AnxA5(+)/PI(+)) apo ones. Both forms of blebs contain apo-induced chromatin modifications and are efficiently phagocytosed by dendritic cell (DC). Uptake by DC of late, but also early apo blebs, stimulate DC to produce IL-6. This bleb-induced effect on DC may be an important step in the initiation of the autoimmune responses in SLE.

Microtubule function and its relation to cellular development and the yeast cell cycle in Wangiella dermatitidis.

The microtubule inhibitor nocodazole (methyl-5-[2-(thienylcarbonyl)-1H-benzimidazol-2-yl]-carbamate) prevented nuclear migration and nuclear division in yeasts and developing multicellular forms of the polymorphic fungus Wangiella dermatitidis. It did not prevent yeast bud formation during at least two or three budding cycles, and caused yeasts to accumulate as premitotic forms with one to three buds. The effects of the drug suggested that at least three control pathways were involved in the yeast cell cycle; that the nocodazole block point was separate from the execution points of two temperature-sensitive mutations which lead to multicellularity; and that microtubules were controlling neither the yeast budding process nor the development of multicellular forms.

Effects of monoclonal anti-H-2Ld and anti-H-2Dd alloantibodies in the immunological enhancement of skin grafts and neonatal heart grafts in the mouse.

Three anti-H-2Ld and two anti-H-2Dd monoclonal alloantibodies were analyzed for their capacity to enhance skin graft and neonatal heart graft survival. Of two anti-H-2Ld antibodies with the same specificity but with different isotypes, IgG2a antibody 30-5-7S prolonged graft survival in a skin graft combination with an Ld difference, whereas IgM antibodies did not. A second IgG2a antibody, but with a specificity different from 30-5-7S, was ineffective on its own. However, when mixed with 30-5-7S, skin graft survival was augmented as compared with the prolongation by 30-5-7S alone. Enhancement by anti-H-2Ld antibodies was dependent on the extent of the H-2 graft barrier. It was abrogated on extension of the graft barrier to a D-end H-2 difference by using the B10.A----B10.BR combination. Also, anti-Dd antibodies, either alone or in combination with anti-Ld, were ineffective in this skin graft combination. By using the same graft combination but the less immunogenic neonatal heart graft model, anti-Ld antibodies were still ineffective, but both anti-Dd antibodies were able to enhance graft survival from 15 to 22 days. When mixed with anti-Ld antibody 30-5-7S, graft survival was augmented further to 30 days. These results indicate that two kinds of enhancing alloantibodies may be distinguished. One category interacts with immunodominant epitopes on H-2 molecules, but their effectiveness may be limited to a particular H-2 difference, because immunodominance may vary from one graft barrier to another. In the second category, antibodies are ineffective on their own but they are able to potentiate the effects of antibodies of the first kind. These allocations are relative, however, because they are dependent on the type of graft examined.

Dark isomerization of retinals in the presence of phosphatidylethanolamine.

1. Dark incubation of retinoids (retinyl ester, retinol, retinal, retinaloxime) in suspensions of rod outer segment membranes leads to substantial isomerization (and partial degradation) in the case of retinals only. 2. All-trans, 13-cis and 9-cis-retinal all isomerize at the delta 13 double bond leading to an equilibrium with approximately 75% trans and 25% cis isomer at this bond (all-trans in equilibrium 13-cis and 9-cis in equilibrium 9,13-dicis). 11-cis-Retinal isomerizes irreversibly to a mixture of all-trans and 13-cis-retinal. 3. The active compound appears to be phosphatidylethanolamine present in the membrane. The amino group and the phosphate, as well as the hydrophobic part of the phospholipid are essential. 4. At least three factors are important for the phosphatidylethanolamine-catalyzed isomerization as studied with the 13-cis isomer: the concentration of phosphatidylethanolamine, the concentration of Schiff base between retinal and phosphatidylethanolamine and the presence of lipid aggregates. 5. Based on these observations a mechanism is proposed, which satisfactorily explains the specificity of the isomerization pattern. 6. It is suggested that reisomerization of all-trans to 11-cis retinal in vivo takes place by fixation of all-trans retinal on an adequate surface (e.g. opsin) and a localized nucleophilic attack on the C-11 atom, followed by trapping of the isomerized chromophore by opsin. 7. It is further concluded that retinal does not occur in vivo as a free intermediate. Direct transfer from one protein to another (opsin, retinol dehydrogenase, retinal binding proteins) seems to take place.

No constitutive defect in phagocytosis of apoptotic cells by resident peritoneal macrophages from pre-morbid lupus mice.

Antibodies against nucleosomes are a hallmark of systemic lupus erythematosus (SLE). Nucleosomes are uniquely formed during apoptosis, through cleavage of chromatin by nucleases. Increased exposure of nucleosomes to the immune system could play a role in the induction of the autoimmune repertoire in SLE. To determine whether there exists a constitutive defect in the clearance of apoptotic cells, resident peritoneal macrophages from pre-morbid SLE-prone MRL and New Zealand (NZ) mice were analysed for their efficacy to phagocytose apoptotic cells in vitro. Although differences in phagocytic efficacy of up to 50% between different strains of mice were found, these were not related to SLE development. To evaluate whether macrophages from SLE-prone mice are more susceptible to phagocytic 'exhaustion', resident peritoneal macrophages were challenged by 20 h of additional culture in the presence of apoptotic cells. In both lupus and control strains this led to an increased capacity to phagocytose fresh apoptotic cells (increase between 15 and 92%). As a control, macrophages from all strains were also exposed to 20 h of additional culture without apoptotic cells. Under this condition resident peritoneal macrophages from all SLE-prone strains, and of the SLE-parental strain NZB, displayed a significant decrease in their efficacy to phagocytose apoptotic cells (decrease between 16 and 55%). Together, these findings do not support the hypothesis that a constitutive defect in the clearance of apoptotic cells, as evaluated by testing resident peritoneal macrophages, plays an important role in the induction of SLE.

Mapping of the Saccharomyces cerevisiae CDC3, CDC25, and CDC42 genes to chromosome XII by chromosome blotting and tetrad analysis.

CDC3, CDC25 and CDC42 were localized to chromosome XII by hybridizing the cloned genes to Southern blots of chromosomes separated by orthogonal-field-alternation gel electrophoresis. Meiotic tetrad analyses further localized these genes to the region distal to the RDN1 locus on the right arm of the chromosome. The STE11 gene, which had previously been mapped to chromosome XII (Chaleff and Tatchell, 1985), was found to be tightly linked to ILV5. The data suggest a map order of CEN12-RDN1-CDC42-(CDC25-CDC3)-(ILV5- STE11)-URA4. Certain oddities of the data set raise the possibility that there may be constraints on the patterns of recombination in this region of chromosome XII.