Cryopreservation of two species of the multicellular volvocine green algal genus Astrephomene.

BACKGROUND: Astrephomene is an interesting green algal genus that, together with Volvox, shows convergent evolution of spheroidal multicellular bodies with somatic cells of the colonial or multicellular volvocine lineage. A recent whole-genome analysis of A. gubernaculifera resolved the molecular-genetic basis of such convergent evolution, and two species of Astrephomene were described. However, maintenance of culture strains of Astrephomene requires rapid inoculation of living cultures, and cryopreserved culture strains have not been established in public culture collections. RESULTS: To establish cryopreserved culture strains of two species of Astrephomene, conditions for cryopreservation of the two species were investigated using immature and mature vegetative colonies and two cryoprotectants: N,N-dimethylformamide (DMF) and hydroxyacetone (HA). Rates of cell survival of the A. gubernaculifera or A. perforata strain after two-step cooling and freezing in liquid nitrogen were compared between different concentrations (3 and 6%) of DMF and HA and two types of colonies: immature colonies (small colonies newly released from the parent) and mature colonies (large colonies just before daughter colony formation). The highest rate of survival [11 ± 13% (0.36-33%) by the most probable number (MPN) method] of A. gubernaculifera strain NIES-4017 (established in 2014) was obtained when culture samples of immature colonies were subjected to cryogenic treatment with 6% DMF. In contrast, culture samples of mature colonies subjected to 3% HA cryogenic treatment showed the highest "MPN survival" [5.5 ± 5.9% (0.12-12%)] in A. perforata. Using the optimized cryopreservation conditions for each species, survival after freezing in liquid nitrogen was examined for six other strains of A. gubernaculifera (established from 1962 to 1981) and another A. perforata strain maintained in the Microbial Culture Collection at the National Institute for Environmental Studies (MCC-NIES). We obtained ≥0.1% MPN survival of the A. perforata strain. However, only two of the six strains of A. gubernaculifera showed ≥0.1% MPN survival. By using the optimal cryopreserved conditions obtained for each species, five cryopreserved strains of two species of Astrephomene were established and deposited in the MCC-NIES. CONCLUSIONS: The optimal cryopreservation conditions differed between the two species of Astrephomene. Cryopreservation of long-term-maintained strains of A. gubernaculifera may be difficult; further studies of cryopreservation of these strains are needed.

CYP broth: a tool for Yersinia pestis isolation in ancient culture collections and field samples.

We developed a simple new selective LB-based medium, named CYP broth, suitable for recovering long-term stored Y. pestis subcultures and for isolation of Y. pestis strains from field-caught samples for the Plague surveillance. It aimed to inhibit the growth contaminating microorganisms and enrich Y. pestis growth through iron supplementation. The performance of CYP broth on microbial growth from different gram-negative and gram-positive strains from American Type Culture Collection (ATCC®) and other clinical isolates, field-caught rodent samples, and more importantly, on several vials of ancient Y. pestis subcultures was evaluated. Additionally, other pathogenic Yersinia species such as Y. pseudotuberculosis and Y. enterocolitica were also successfully isolated with CYP broth. Selectivity tests and bacterial growth performance on CYP broth (LB broth supplemented with Cefsulodine, Irgasan, Novobiocin, nystatin and ferrioxamine E) were evaluated in comparison with LB broth without additive; LB broth/CIN, LB broth/nystatin and with traditional agar media including LB agar without additive, and LB agar and Cefsulodin-Irgasan-Novobiocin Agar (CIN agar) supplemented with 50 µg/mL of nystatin. Of note, the CYP broth had a recovery twofold higher than those of the CIN supplemented media or other regular media. Additionally, selectivity tests and bacterial growth performance were also evaluated on CYP broth in the absence of ferrioxamine E. The cultures were incubated at 28 °C and visually inspected for microbiological growth analysis and O.D.625 nm measurement between 0 and 120 h. The presence and purity of Y. pestis growth were confirmed by bacteriophage and multiplex PCR tests. Altogether, CYP broth provides an enhanced growth of Y. pestis at 28 °C, while inhibiting contaminant microorganisms. The media is a simple, but powerful tool to improve the reactivation and decontamination of ancient Y. pestis culture collections and for the isolation of Y. pestis strains for the Plague surveillance from various backgrounds. KEY POINTS: • The newly described CYP broth improves the recuperation of ancient/contaminated Yersinia pestis culture collections • CYP broth was also efficient in reducing environmental contamination in field-capture samples, improving Y. pestis isolation • CYP broth can also be used for the isolation of Y. enterocolitica and Y. pseudotuberculosis.

Large-scale screening of yeast strains that can utilize proline.

Proline contributes to the taste and flavor of foods. The yeast Saccharomyces cerevisiae poorly assimilates proline during fermentation processes, resulting in the accumulation of proline in fermentative products. We performed here a screening of in total 1138 yeasts to obtain strains that better utilize proline. Our results suggest that proline utilization occurs in the genera of Zygoascus, Galactomyces, and Magnusiomyces.

Untangling filamentous marine cyanobacterial diversity from the coast of South Florida with the description of Vermifilaceae fam. nov. and three new genera: Leptochromothrix gen. nov., Ophiophycus gen. nov., and Vermifilum gen. nov.

Benthic cyanobacterial mats are an integral component of aquatic communities in tropical marine waters. These mats can develop into massive nuisances at risk of expansion due to climate change. The extent of diversity occurring within these mats, still remains largely unexplored, especially in Florida. To reveal this diversity, coastal environments of South Florida were sampled and subsequently processed for isolation and systematic identification. Three new genera are proposed based on the molecular phylogeny, morphology, and ecology. These new genera are characterized by discoid cells and homocytous, unbranched filaments without sheaths. Individual genus morphological differences include either rounded bent, rounded, or conical rounded apical cells. A unique molecular fingerprint including a base pair insert within the 16S rRNA gene sequence and genetic similarities facilitates the delimitation of a novel family Vermifilaceae. Using the polyphasic approach, our research presents three new genera and four new species of marine cyanobacteria inhabiting coastal ecosystems of South Florida.

Celebrating INVAM: 35 years of the largest living culture collection of arbuscular mycorrhizal fungi.

The International Culture Collection of (Vesicular-) Arbuscular Mycorrhizal Fungi-INVAM-the largest living culture collection of arbuscular mycorrhizal fungi (AMF) celebrated its 35th year in 2020. The authors record here the mission and goals of INVAM, its contribution as a living culture collection, some historical aspects of INVAM, and describe the advances in mycorrhizology and AMF systematics after INVAM moved to West Virginia University. This commentary emphasizes the importance of a living culture collection to preserve germplasm and to educate and assist researchers in mycorrhizal science.

Public Microbial Resource Centers: Key Hubs for Findable, Accessible, Interoperable, and Reusable (FAIR) Microorganisms and Genetic Materials.

In the context of open science, the availability of research materials is essential for knowledge accumulation and to maximize the impact of scientific research. In microbiology, microbial domain biological resource centers (mBRCs) have long-standing experience in preserving and distributing authenticated microbial strains and genetic materials (e.g., recombinant plasmids and DNA libraries) to support new discoveries and follow-on studies. These culture collections play a central role in the conservation of microbial biodiversity and have expertise in cultivation, characterization, and taxonomy of microorganisms. Information associated with preserved biological resources is recorded in databases and is accessible through online catalogues. Legal expertise developed by mBRCs guarantees end users the traceability and legality of the acquired material, notably with respect to the Nagoya Protocol. However, awareness of the advantages of depositing biological materials in professional repositories remains low, and the necessity of securing strains and genetic resources for future research must be emphasized. This review describes the unique position of mBRCs in microbiology and molecular biology through their history, evolving roles, expertise, services, challenges, and international collaborations. It also calls for an increased deposit of strains and genetic resources, a responsibility shared by scientists, funding agencies, and publishers. Journal policies requesting a deposit during submission of a manuscript represent one of the measures to make more biological materials available to the broader community, hence fully releasing their potential and improving openness and reproducibility in scientific research.

Collection, transport and storage procedures for blood culture specimens in adult patients: recommendations from a board of Italian experts.

Bloodstream infections (BSIs) remain a potentially life-threatening condition. The gold standard for the diagnosis of BSI is still blood cultures (BCs), and the diagnostic yield depends on clinical and technical factors that have an impact on collection and transportation. Hence, monitoring of the entire pre-analytical process from blood collection to transportation to the microbiology laboratory is critical. To optimize the clinical impact of the diagnostic and therapeutic procedures, a multidisciplinary approach and univocal protocols are mandatory. A board of specialists discussed the available evidence on the pre-analytical process and produced the present document to guide physicians and nurses on the ideal execution of BC: (1) timing and preparation for blood collection; (2) skin antisepsis; (3) blood volume; (4) sampling method and safety; (5) medium to be used; (6) time to BC transportation; and (7) quality assurance and quality management.

National production of certified reference fungal cultures.

Reference fungal cultures (RFCs) are essential for the internal quality control of laboratories. The production of these cultures requires standardized procedures (IRAM 14950:2016 and ISO 17034:2016 standards) carried out by a recognized and accredited laboratory. The aim of this work was to produce RFC in paper disks of autochthonous strains, characterized by two, homogeneous and stable reference methods traceable at species level. RFC were produced using 14 regional species (7 yeasts and 7 filamentous fungi) from the fungal culture collection (DMic). Paper disks were impregnated with a culture suspension, dried and packed. Homogeneity, viability, identity and purity were verified. Short- and long-term stability at different temperatures and storage times were studied. Characterization of each strain allowed to confirm its identity and to ensure its traceability at international level. Produced batches were homogeneous and stable at -20±5°C for 30 months. This method of production was adequate to produce homogeneous and stable RFC with phenotypic and genotypic characteristics correctly defined and internationally traceable. Standardized procedures were developed for the production of certified RFC that could be transferred to other microorganisms. Providing RFC that represent regional strains allows laboratories to produce more reliable results with a favorable impact on medical diagnosis, the environment or the food industry.

Genetic variation during long-term preservation of bacteria in public culture collections.

Phenotypic and genetic changes during long-term preservation have been observed in microbial strains at culture collections (CCs). It is imperative to verify the effects of these changes on quality of the strains preserved at CCs. In this study, we performed genome-wide single-nucleotide polymorphism (SNP) analysis of different production lots, which had been derived from the same origin and preserved at the NITE Biological Resource Center (NBRC) for a 4-38-year period by the vacuum liquid drying method at 4 °C. The analysis was conducted for three sets of lots derived from Cellulomonas fimi NBRC 15513T, Corynebacterium glutamicum NBRC 12168T, and Saccharomonospora viridis NBRC 12207T. SNPs were found in all sets studied for comparison purposes. In sets of two or three lots, genomic SNPs were found in both non-coding sequences (non-CDSs) and in coding sequences (CDSs), and the SNPs in the CDSs resulted in non-synonymous mutations. These data indicated that genomic variation occurred during long-term preservation.

In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence.

The antioxidant potential (AP) is an important nutritional property of foods, as increased oxidative stress is involved in most diet-related chronic diseases. In dairy products, the protein fraction contains antioxidant activity, especially casein. Other antioxidants include: antioxidant enzymes; lactoferrin; conjugated linoleic acid; coenzyme Q10; vitamins C, E, A and D3; equol; uric acid; carotenoids; and mineral activators of antioxidant enzymes. The AP of dairy products has been extensively studied in vitro, with few studies in animals and human subjects. Available in vivo studies greatly differ in their design and objectives. Overall, on a 100 g fresh weight-basis, AP of dairy products is close to that of grain-based foods and vegetable or fruit juices. Among dairy products, cheeses present the highest AP due to their higher protein content. AP of milk increases during digestion by up to 2·5 times because of released antioxidant peptides. AP of casein is linked to specific amino acids, whereas ß-lactoglobulin thiol groups play a major role in the AP of whey. Thermal treatments such as ultra-high temperature processing have no clear effect on the AP of milk. Raw fat-rich milks have higher AP than less fat-rich milk, because of lipophilic antioxidants. Probiotic yoghurts and fermented milks have higher AP than conventional yoghurt and milk because proteolysis by probiotics releases antioxidant peptides. Among the probiotics, Lactobacillus casei/acidophilus leads to the highest AP. The data are insufficient for cheese, but fermentation-based changes appear to make a positive impact on AP. In conclusion, AP might participate in the reported dairy product-protective effects against some chronic diseases.

Identification and characterization of a 20ß-HSDH from the anaerobic gut bacterium Butyricicoccus desmolans ATCC 43058.

Members of the gastrointestinal microbiota are known to convert glucocorticoids to androstanes, which are subsequently converted to potent androgens by other members of the gut microbiota or host tissues. Butyricicoccus desmolans and Clostridium cadaveris have previously been reported for steroid-17,20-desmolase and 20ß-hydroxysteroid dehydrogenase (HSDH) activities that are responsible for androstane formation from cortisol; however, the genes encoding these enzymes have yet to be reported. In this work, we identified and located a gene encoding 20ß-HSDH in both B. desmolans and C. cadaveris The 20ß-HSDH of B. desmolans was heterologously overexpressed and purified from Escherichia coli The enzyme was determined to be a homotetramer with subunit molecular mass of 33.8 ± 3.7 kDa. The r20ß-HSDH displayed pH optimum in the reductive direction at pH 9.0 and in the oxidative direction at pH 7.0-7.5 with (20ß-dihydro)cortisol and NAD(H) as substrates. Cortisol is the preferred substrate with Km , 0.80 ± 0.06 µM; Vmax , 30.36 ± 1.97 µmol·min-1; Kcat , 607 ± 39 µmol·µM-1·min-1; Kcat /Km , 760 ± 7.67. Phylogenetic analysis of the 20ß-HSDH from B. desmolans suggested that the 20ß-HSDH is found in several Bifidobacterium spp, one of which was shown to express 20ß-HSDH activity. Notably, we also identified a novel steroid-17,20-desmolase-elaborating bacterium, Propionimicrobium lymphophilum, a normal inhabitant of the urinary tract.

Mechanisms responsible for the hypocholesterolaemic effect of regular consumption of probiotics.

CVD affect a large proportion of the world's population, with dyslipidaemia as the major risk factor. The regular consumption of both probiotic bacteria and yeast has been associated with improvement in the serum lipid profile. Thus, the present review aims to describe and discuss the potential mechanisms responsible for the hypocholesterolaemic effect of regular consumption of probiotic bacteria and yeast. Regarding the hypocholesterolaemic effect of probiotic bacteria, the potential mechanisms responsible include: deconjugation of bile salts; modulation of lipid metabolism; and decreased absorption of intestinal cholesterol through co-precipitation of intestinal cholesterol with the deconjugated bile salts, incorporation and assimilation of cholesterol in the cell membrane of the probiotics, intestinal conversion of cholesterol in coprostanol, and inhibition of the expression of the intestinal cholesterol transporter Niemann-Pick C1 like 1 (NPC1L1) in the enterocytes. The potential mechanisms responsible for the hypocholesterolaemic effect of probiotic yeasts include: deconjugation of bile salts; co-precipitation of intestinal cholesterol with the deconjugated bile salts; incorporation and assimilation of cholesterol in the cell membrane; and inhibition of hepatic cholesterol synthesis. The regular consumption of probiotic bacteria and yeast, as a non-pharmaceutical approach to help manage cardiovascular risk, holds promise, according to the beneficial hypocholesterolaemic effects described herein. However, the hypocholesterolaemic effects vary according to the strains used, the physiological state of the host, and the type of diet to which the probiotics are added. Further studies are necessary to fill the gaps with regard to the knowledge related to this topic.

Obtention and characterization of the recombinant simian Interleukin-15 in Escherichia coli for the preclinical assessment of an IL-15-based therapeutic vaccine.

Recombinant simian IL-15 (siIL-15) was obtained for the preclinical assessment of an anti-human IL-15 vaccine. For this purpose, the cDNA from peripheral blood mononuclear cells of a Macaca fascicularis monkey was cloned into a pIL-2 vector. The siIL-15 was expressed in Escherichia coli strain W3110 as an insoluble protein which accounted for 13% of the total cellular proteins. Inclusion bodies were solubilized in an 8 M urea solution, which was purified by ion exchange and reverse phase chromatography up to 92% purity. The protein identity was validated by electrospray ionization-mass spectrometry, confirming the presence of the amino acids which distinguish the siIL-15 from human IL-15. The purified siIL-15 stimulates the proliferation of cytotoxic T-lymphocytes line (CTLL)-2 and Kit 225 cells with EC50 values of 3.1 and 32.5 ng/mL, respectively. Antisera from modified human IL-15-immunized macaques were reactive to human and simian IL-15 in enzyme-linked immunosorbent assays. Moreover, the anti-human IL-15 antibodies from immune sera inhibited siIL-15 activity in CTLL-2 and Kit 225 cells, supporting the activity and purity of recombinant siIL-15. These results indicate that the recombinant siIL-15 is biologically active in two IL-15-dependent cell lines, and it is also suitable for the preclinical evaluation of an IL-15-based therapeutic vaccine.

Yeast culture collections in the twenty-first century: new opportunities and challenges.

The twenty-first century has brought new opportunities and challenges to yeast culture collections, whether they are long-standing or recently established. Basic functions such as archiving, characterizing and distributing yeasts continue, but with expanded responsibilities and emerging opportunities. In addition to a number of well-known, large public repositories, there are dozens of smaller public collections that differ in the range of species and strains preserved, field of emphasis and services offered. Several collections have converted their catalogues to comprehensive databases and synchronize them continuously through public services, making it easier for users worldwide to locate a suitable source for specific yeast strains and the data associated with these yeasts. In-house research such as yeast taxonomy continues to be important at culture collections. Because yeast culture collections preserve a broad diversity of species and strains within a species, they are able to make discoveries in many other areas as well, such as biotechnology, functional, comparative and evolution genomics, bioprocesses and novel products. Due to the implementation of the Convention of Biological Diversity (CBD) and the Nagoya Protocol (NP), there are new requirements for both depositors and users to ensure that yeasts were collected following proper procedures and to guarantee that the country of origin will be considered if benefits arise from a yeast's utilization. Intellectual property rights (IPRs) are extremely relevant to the current access and benefit-sharing (ABS) mechanisms; most research and development involving genetic resources and associated traditional knowledge will be subject to this topic. Copyright © 2016 John Wiley & Sons, Ltd.

Antifungal effect and pore-forming action of lactoferricin B like peptide derived from centipede Scolopendra subspinipes mutilans.

The centipede Scolopendra subspinipes mutilans has been a medically important arthropod species by using it as a traditional medicine for the treatment of various diseases. In this study, we derived a novel lactoferricin B like peptide (LBLP) from the whole bodies of adult centipedes, S. s. mutilans, and investigated the antifungal effect of LBLP. LBLP exerted an antifungal and fungicidal activity without hemolysis. To investigate the antifungal mechanism of LBLP, a membrane study with propidium iodide was first conducted against Candida albicans. The result showed that LBLP caused fungal membrane permeabilization. The assays of the three dimensional flow cytometric contour plot and membrane potential further showed cell shrinkage and membrane depolarization by the membrane damage. Finally, we confirmed the membrane-active mechanism of LBLP by synthesizing model membranes, calcein and FITC-dextran loaded large unilamellar vesicles. These results showed that the antifungal effect of LBLP on membrane was due to the formation of pores with radii between 0.74nm and 1.4nm. In conclusion, this study suggests that LBLP exerts a potent antifungal activity by pore formation in the membrane, eventually leading to fungal cell death.

Vascular targeting to the SST2 receptor improves the therapeutic response to near-IR two-photon activated PDT for deep-tissue cancer treatment.

BACKGROUND: Broader clinical acceptance of photodynamic therapy is currently hindered by (a) poor depth efficacy, and (b) predisposition towards establishment of an angiogenic environment during the treatment. Improved depth efficacy is being sought by exploiting the NIR tissue transparency window and by photo-activation using two-photon absorption (2PA). Here, we use two-photon activation of PDT sensitizers, untargeted and targeted to SST2 receptors or EGF receptors, to achieve deep tissue treatment. METHODS: Human tumor lines, positive or negative for SST2r expression were used, as well as murine 3LL cells and bovine aortic endothelial cells. Expression of SST2 receptors on cancer cells and tumor vasculature was evaluated in vitro and frozen xenograft sections. PDT effects on tumor blood flow were followed using in vivo scanning after intravenous injection of FITC conjugated dextran 150K. Dependence of the PDT efficacy on the laser pulse duration was evaluated. Effectiveness of targeting to vascular SST2 receptors was compared to that of EGF receptors, or no targeting. RESULTS: Tumor vasculature stained for SST2 receptors even in tumors from SST2 receptor negative cell lines, and SST2r targeted PDT led to tumor vascular shutdown. Stretching the pulse from ~120fs to ~3ps led to loss of the PDT efficacy especially at greater depth. PDT targeted to SST2 receptors was much more effective than untargeted PDT or PDT targeted to EGF receptors. GENERAL SIGNIFICANCE: The use of octreotate to target SST2 receptors expressed on tumor vessels is an excellent approach to PDT with few recurrences and some long term cures.

Honokiol: a non-adipogenic PPARγ agonist from nature.

BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPARγ) agonists are clinically used to counteract hyperglycemia. However, so far experienced unwanted side effects, such as weight gain, promote the search for new PPARγ activators. METHODS: We used a combination of in silico, in vitro, cell-based and in vivo models to identify and validate natural products as promising leads for partial novel PPARγ agonists. RESULTS: The natural product honokiol from the traditional Chinese herbal drug Magnolia bark was in silico predicted to bind into the PPARγ ligand binding pocket as dimer. Honokiol indeed directly bound to purified PPARγ ligand-binding domain (LBD) and acted as partial agonist in a PPARγ-mediated luciferase reporter assay. Honokiol was then directly compared to the clinically used full agonist pioglitazone with regard to stimulation of glucose uptake in adipocytes as well as adipogenic differentiation in 3T3-L1 pre-adipocytes and mouse embryonic fibroblasts. While honokiol stimulated basal glucose uptake to a similar extent as pioglitazone, it did not induce adipogenesis in contrast to pioglitazone. In diabetic KKAy mice oral application of honokiol prevented hyperglycemia and suppressed weight gain. CONCLUSION: We identified honokiol as a partial non-adipogenic PPARγ agonist in vitro which prevented hyperglycemia and weight gain in vivo. GENERAL SIGNIFICANCE: This observed activity profile suggests honokiol as promising new pharmaceutical lead or dietary supplement to combat metabolic disease, and provides a molecular explanation for the use of Magnolia in traditional medicine.

Synthesis and antimicrobial activity of cysteine-free coprisin nonapeptides.

Coprisin is a 43-mer defensin-like peptide from the dung beetle, Copris tripartitus. CopA3 (LLCIALRKK-NH2), a 9-mer peptide containing a single free cysteine residue at position 3 of its sequence, was derived from the α-helical region of coprisin and exhibits potent antibacterial and anti-inflammatory activities. The single cysteine implies a tendency for dimerization; however, it remains unknown whether this cysteine residue is indispensible for CopA3's antimicrobial activity. To address this issue, in the present study we synthesized eight cysteine-substituted monomeric CopA3 analogs and two dimeric analogs, CopA3 (Dimer) and CopIK (Dimer), and evaluated their antimicrobial effects against bacteria and fungi, as well as their hemolytic activity toward human erythrocytes. Under physiological conditions, CopA3 (Mono) exhibits a 6/4 (monomer/dimer) molar ratio in HPLC area percent, indicating that its effects on bacterial strains likely reflect a CopA3 (Mono)/CopA3 (Dimer) mixture. We also report the identification of CopW, a new cysteine-free nonapeptide derived from CopA3 that has potent antimicrobial activity with virtually no hemolytic activity. Apparently, the cysteine residue in CopA3 is not essential for its antimicrobial function. Notably, CopW also exhibited significant synergistic activity with ampicillin and showed more potent antifungal activity than either wild-type coprisin or melittin.

Rapid desensitization of mice with anti-FcγRIIb/FcγRIII mAb safely prevents IgG-mediated anaphylaxis.

BACKGROUND: Stimulatory IgG receptors (FcγRs) on bone marrow-derived cells contribute to the pathogenesis of several autoimmune and inflammatory disorders. Monoclonal antibodies that block FcγRs might suppress these diseases, but they can induce anaphylaxis. OBJECTIVE: We wanted to determine whether a rapid desensitization approach can safely suppress IgG/FcγR-mediated anaphylaxis. METHODS: Mice were injected with serially increasing doses of 2.4G2, a rat mAb that blocks the inhibitory FcγR, FcγRIIb, and the stimulatory receptor, FcγRIII. Rectal temperature was used to detect the development of anaphylaxis. Passive and active IgG-mediated anaphylaxis were evaluated in mice that had been rapidly desensitized with 2.4G2 or mock-desensitized in mice in which monocyte/macrophages, basophils, or neutrophils had been depleted or desensitized and in mice in which FcγRI, FcγRIII, and/or FcγRIV had been deleted or blocked. RESULTS: Rapid desensitization with 2.4G2 prevented 2.4G2-induced shock and completely suppressed IgG-mediated anaphylaxis. Rapid desensitization of ovalbumin-sensitized mice with 2.4G2 was safer and more effective than rapid desensitization with ovalbumin. 2.4G2 treatment completely blocked FcγRIII and removed most FcγRI and FcγRIV from nucleated peripheral blood cells. Because IgG(2a)-mediated anaphylaxis was partially FcγRI and FcγRIV dependent, the effects of 2.4G2 on FcγRI and FcγRIV were probably crucial for its complete inhibition of IgG(2a)-mediated anaphylaxis. IgG(2a)-mediated anaphylaxis was partially inhibited by depletion or desensitization of monocyte/macrophages, basophils, or neutrophils. CONCLUSION: IgG-mediated anaphylaxis can be induced by ligation of FcγRI, FcγRIII, or FcγRIV on monocycte/macrophages, basophils, or neutrophils and can be safely suppressed by rapid desensitization with anti-FcγRII/RIII mAb. A similar approach may safely suppress other FcγR-dependent immunopathology.