Free Release Research Articles

Photopolymerization of highly filled dimethacrylate-based composites using Type I or Type II photoinitiators and varying co-monomer ratios

ObjectivesThe use of a Type I photoinitiator (monoacylphosphine oxide, MAPO) was described as advantageous in a model formulation, as compared to the conventional Type II photoinitiator (Camphorquinone, CQ). The aim of the present work was to study the kinetics of polymerization of various composite mixtures (20–40–60–80mol%) of bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (BisGMA/TegDMA) containing either CQ or MAPO, based on real-time measurements and on the characterization of various post-cure characteristics. MethodsPolymerization kinetics were monitored by Fourier-transform near-infrared spectroscopy (FT-NIRS) and dielectric analysis (DEA). A range of postcure properties was also investigated. ResultsFT-NIRS and DEA proved complementary to follow the fast kinetics observed with both systems. Autodecceleration occurred after ≈1s irradiation for MAPO-composites and ≈5–10s for CQ-composites. Conversion decreased with increasing initial viscosity for both photoinitiating systems. However despite shorter light exposure (3s for MAPO vs 20s for CQ-composites), MAPO-composites yielded higher conversions for all co-monomer mixtures, except at 20mol% BisGMA, the less viscous material. MAPO systems were associated with increased amounts of trapped free radicals, improved flexural strength and modulus, and reduced free monomer release for all co-monomer ratios, except at 20mol% BisGMA. SignificanceThis work confirms the major influence of the initiation system both on the conversion and network cross-linking of highly-filled composites, and further highlights the advantages of using MAPO photoinitiating systems in highly-filled dimethacrylate-based composites provided that sufficient BisGMA content (>40mol%) and adapted light spectrum are used.

Wazing the Information Super Highway: Linking the World’s Open Government Data Resources

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Uncertainty assessment in the free release measurement by gamma spectrometry of rotating waste drums

The assessment of uncertainty in free release measurements by integral gamma scanning method is described and applied to the measurement of homogeneous and heterogeneous waste drums. It is based on the propagation of distributions using the Monte Carlo method. In addition, two techniques for the uncertainty reduction are also described. The first technique makes use of containers constructed from two concentric cylinders and the second technique is based on the measurement of a group of waste drums. It is proved that the uncertainty of clearance measurements can be reduced using both techniques.

Distribution of radionuclides in an iron calibration standard for a free release measurement facility

A Europallet-sized calibration standard composed of 12 grey cast iron tubes contaminated with 60Co and 110mAg with a mass of 246kg was developed. As the tubes were produced through centrifugal casting it was of particular concern to study the distribution of radionuclides in the radial direction of the tubes. This was done by removing 72 small samples (swarf) of ~0.3g each on both the inside and outside of the tubes. All of the samples were measured in the underground laboratory HADES.

Lessons Learned on the Presentation of Scan Data.

Technicians performed a radiological survey of a surplus metal tank to support disposition planning at an Oak Ridge, TN, site. The survey included radiation scans to identify contamination and, if identified, define the boundary and magnitude of contamination. Fixed-point 1-min measurements were also collected at randomly selected locations for comparison against the site's free release limit of 5,000 disintegrations per minute per 100 cm (dpm 100 cm) (0.83 Bq cm). Scan data were recorded using a data logger as a means to document surveyor observation-logged data captured at 1-s intervals and converted to counts per minute (cpm) by the data logger software were presented in the project report. Both the qualitative scan data (in cpm) and the quantitative direct measurements (in dpm 100 cm) were reported for completeness, so stakeholders had all available information to support disposition decisions. However, a new stakeholder-introduced to the project at the reporting phase of work-used the instrument efficiency and background data to convert the scan data from cpm to dpm 100 cm, then compared the converted results to the site limit. Many of the converted values exceeded 5,000 dpm 100 cm. This resulted in delays in tank disposition and additional project costs that could have been avoided if the proper use and interpretation of scan data and implications of radon progeny buildup on oxidized metal surfaces had been better communicated.

Remote electrical arc suppression by laser filamentation

We investigate the interaction of narrow plasma channels formed in the filamentation of ultrashort laser pulses, with a DC high voltage. The laser filaments prevent electrical arcs by triggering corona that neutralize the high-voltage electrodes. This phenomenon, that relies on the electric field modulation and free electron release around the filament, opens new prospects to lightning and over-voltage mitigation.

Cytosolic Nuclease TREX1 Regulates Oligosaccharyltransferase Activity Independent of Nuclease Activity to Suppress Immune Activation

TREX1 is an endoplasmic reticulum (ER)-associated negative regulator of innate immunity. TREX1 mutations are associated with autoimmune and autoinflammatory diseases. Biallelic mutations abrogating DNase activity cause autoimmunity by allowing immunogenic self-DNA to accumulate, but it is unknown how dominant frameshift (fs) mutations that encode DNase-active but mislocalized proteins cause disease. We found that the TREX1 C terminus suppressed immune activation by interacting with the ER oligosaccharyltransferase (OST) complex and stabilizing its catalytic integrity. C-terminal truncation of TREX1 by fs mutations dysregulated the OST complex, leading to free glycan release from dolichol carriers, as well as immune activation andautoantibody production. A connection between OST dysregulation and immune disorders was demonstrated in Trex1(-/-) mice, TREX1-V235fs patient lymphoblasts, and TREX1-V235fs knock-in mice. Inhibiting OST with aclacinomycin corrects the glycan and immune defects associated with Trex1 deficiency or fs mutation. This function of the TREX1 C terminus suggests a potential therapeutic option for TREX1-fs mutant-associated diseases.

Genotoxic capacity of Cd/Se semiconductor quantum dots with differing surface chemistries.

Quantum dots (QD) have unique electronic and optical properties promoting biotechnological advances. However, our understanding of the toxicological structure–activity relationships remains limited. This study aimed to determine the biological impact of varying nanomaterial surface chemistry by assessing the interaction of QD with either a negative (carboxyl), neutral (hexadecylamine; HDA) or positive (amine) polymer coating with human lymphoblastoid TK6 cells. Following QD physico-chemical characterisation, cellular uptake was quantified by optical and electron microscopy. Cytotoxicity was evaluated and genotoxicity was characterised using the micronucleus assay (gross chromosomal damage) and the HPRT forward mutation assay (point mutagenicity). Cellular damage mechanisms were also explored, focusing on oxidative stress and mitochondrial damage. Cell uptake, cytotoxicity and genotoxicity were found to be dependent on QD surface chemistry. Carboxyl-QD demonstrated the smallest agglomerate size and greatest cellular uptake, which correlated with a dose dependent increase in cytotoxicity and genotoxicity. Amine-QD induced minimal cellular damage, while HDA-QD promoted substantial induction of cell death and genotoxicity. However, HDA-QD were not internalised by the cells and the damage they caused was most likely due to free cadmium release caused by QD dissolution. Oxidative stress and induced mitochondrial reactive oxygen species were only partially associated with cytotoxicity and genotoxicity induced by the QD, hence were not the only mechanisms of importance. Colloidal stability, nanoparticle (NP) surface chemistry, cellular uptake levels and the intrinsic characteristics of the NPs are therefore critical parameters impacting genotoxicity induced by QD.

Carbon Nanotubes Released from an Epoxy-Based Nanocomposite: Quantification and Particle Toxicity.

Studies combining both the quantification of free nanoparticle release and the toxicological investigations of the released particles from actual nanoproducts in a real-life exposure scenario are urgently needed, yet very rare. Here, a new measurement method was established to quantify the amount of free-standing and protruding multiwalled carbon nanotubes (MWCNTs) in the respirable fraction of particles abraded from a MWCNT-epoxy nanocomposite. The quantification approach involves the prelabeling of MWCNTs with lead ions, nanocomposite production, abrasion and collection of the inhalable particle fraction, and quantification of free-standing and protruding MWCNTs by measuring the concentration of released lead ions. In vitro toxicity studies for genotoxicity, reactive oxygen species formation, and cell viability were performed using A549 human alveolar epithelial cells and THP-1 monocyte-derived macrophages. The quantification experiment revealed that in the respirable fraction of the abraded particles, approximately 4000 ppm of the MWCNTs were released as exposed MWCNTs (which could contact lung cells upon inhalation) and approximately 40 ppm as free-standing MWCNTs in the worst-case scenario. The release of exposed MWCNTs was lower for nanocomposites containing agglomerated MWCNTs. The toxicity tests revealed that the abraded particles did not induce any acute cytotoxic effects.

Use of Sub-bandgap Illumination to Improve Radiation Detector Resolution of CdZnTe

The performance of Cd1−x Zn x Te (CZT) materials for room-temperature gamma/x-ray radiation detection continues to improve in terms of material quality and detector design. In our prior publications, we investigated the use of multiple wavelengths of light (in the visible and infrared) to target charge carriers at various trap energies and physical positions throughout crystals. Light exposure significantly alters the charge mobility and improves carrier collection at the anode contact. This study presents an investigation of material performance as a radiation detector during such illumination. The decrease in charge trapping and increase in charge collection due to a higher probability of free electron release from traps contributed to an increase in the resolution-based performance of the detector through controlled illumination. We investigated the performance improvement of CZT crystals with previously known levels of intrinsic defects and secondary phases, at various voltages, light-emitting diode (LED) light wavelengths, and shaping times. Although our setup was clearly not optimized for radiation detector performance, it demonstrated substantial resolution improvements (based on full-width at half-maximum using 662-keV gamma rays from 137Cs upon illumination with 950-nm light) of 16% to 38% in comparison with unilluminated CZT under similar conditions. This manuscript includes discussion of the electrooptic behavior and its effect on performance. Additional testing and fabrication of a detector that incorporates such LED light optimization could lead to improved performance with existing detector-grade materials.

Abstract 1628: Neuropeptide Y (NPY) and its receptor expression in neuroblastoma patients - associations with disease prognosis and patients’ survival

Abstract Neuropeptide Y (NPY) is a sympathetic neurotransmitter, abundantly expressed in neuroblastoma (NB). Previously, we have shown that NPY, acting via its Y2 receptor (Y2R), stimulates proliferation of NB cells and tumor vascularization, while inducible Y5 receptor (Y5R) promotes tumor cell survival and chemoresistance. The aim of the current study was to assess the prognostic value of NPY and its receptor expression in NB. We have tested corresponding samples of RNA, tissue sections and serum from 87 NB patients at various stages of the disease, obtained from the Children's Oncology Group. Samples were analyzed in terms of NPY system expression (NPY, Y2R and Y5R). Protein levels and mRNA in tumor tissue were quantified by immunohistochemistry (IHC) and real time-PCR, respectively, while NPY concentration in serum was measured by ELISA. The expression of other factors implicated in NB development and progression (MYCN, ALK, TrkA III, TrkB and BDNF) were detected on mRNA levels by real time-PCR. For each of the categorical prognostic variables, a Wilcoxon rank-sum or Fisher's exact test were administered to compare NPY and receptor values between groups, and a log-rank test was performed to compare the event-free survival and overall survival between groups. 1) NPY mRNA was detectable in 100% of analyzed tumors. IHC staining revealed that NPY accumulated intracellularly in differentiating and maturing cells, while in undifferentiated NBs a significant amount of the peptide was observed in extracellular spaces, suggesting its free release. In line with this observation, serum concentrations of NPY were higher in the subset of NB patients with undifferentiated and poorly differentiated tumors, as compared to those with differentiating NBs (p-value = 0.03). High serum concentrations of NPY strongly correlated with several adverse prognostic factors (Stage 4, high risk, diploidy, and unfavorable histology) (p-value<0.03) and worse survival (p-value<0.04). 2) Y2R was expressed mainly in undifferentiated NB cells. mRNA of this receptor was detectable in 100% of cases and its levels positively correlated with MYCN expression 3) mRNA of Y5R was detectable in 84% of tumors assessed and correlated with expression of BDNF and its TrkB receptor, factors associated with poor prognosis. High Y5R protein levels marked a population of invasive NB cells. This study validated NPY and its receptors as targets for NB therapy. Serum NPY was the most highly prognostic variable, found to be associated with five NB prognostic factors. Higher NPY levels were correlated with a more detrimental disease phenotype. Citation Format: Susana Galli, Jason Tilan, Arlene Naranjo, Collin Van Ryn, Chao Yang, Jessica Tsuei, Emily Trinh, Joanna B. Kitlinska. Neuropeptide Y (NPY) and its receptor expression in neuroblastoma patients - associations with disease prognosis and patients’ survival. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1628. doi:10.1158/1538-7445.AM2015-1628

Boration modeling of the PWR biological shield using SCALE6.1 hybrid shielding methodology

The PWR biological shield concrete activation is analyzed using SCALE6.1 hybrid deterministic–stochastic shielding methodology. Since accurate geometry representation is a paramount step for this type of shielding calculation involving heterogeneous three dimensional regions (reactor core, thermal shield, downcomer, pressure vessel, cavity, and shield), the Monte Carlo method is the method of choice. A detailed model of a combinatorial geometry, materials and characteristics of a typical PWR reactor was based on the best available data. The sources of ionizing radiation included fission neutrons and photons originating from the HBR-2 benchmark critical core. The activation reduction of reactor biological shield materials was investigated via concrete boration, which is applied when shielding from ionizing neutron radiation is especially important. The concrete boration is the common method for activation reduction in nuclear shields since the 10B has especially high thermal neutron cross section which effectively captures thermalized neutrons and decreases their (n,γ) reaction in structural materials. The reduction of secondary gamma emissions from radiative capture of thermalized neutrons in biological shield has been examined via concrete boration with natural boron (B) and boron carbide (B4C). The possibility of neutron flux mitigation in a biological shield as well as impurity isotopes (59Co, 151Eu, and 153Eu) activity decrease was especially explored. Satisfactory boron concentration which leads to saturation of neutron flux attenuation has been proposed. The activation levels of impurities in concrete, activated above the limit of IAEA clearance for the free release limit, have been estimated. The obtained results showed that activation over IAEA limits is mostly present in a thin layer of borated shield facing the critical reactor core in cavity, while the bulk of the shield is activated below IAEA threshold. The saturation of the neutron flux attenuation was clearly demonstrated for several boron concentrations so even small amounts of boron in biological shield drastically benefit the overall flux reduction.

Hyaluronan, Inflammation, and Breast Cancer Progression.

Breast cancer-induced inflammation in the tumor reactive stroma supports invasion and malignant progression and is contributed to by a variety of host cells including macrophages and fibroblasts. Inflammation appears to be initiated by tumor cells and surrounding host fibroblasts that secrete pro-inflammatory cytokines and chemokines and remodel the extracellular matrix (ECM) to create a pro-inflammatory “cancerized” or tumor reactive microenvironment that supports tumor expansion and invasion. The tissue polysaccharide hyaluronan (HA) is an example of an ECM component within the cancerized microenvironment that promotes breast cancer progression. Like many ECM molecules, the function of native high-molecular weight HA is altered by fragmentation, which is promoted by oxygen/nitrogen free radicals and release of hyaluronidases within the tumor microenvironment. HA fragments are pro-inflammatory and activate signaling pathways that promote survival, migration, and invasion within both tumor and host cells through binding to HA receptors such as CD44 and RHAMM/HMMR. In breast cancer, elevated HA in the peri-tumor stroma and increased HA receptor expression are prognostic for poor outcome and are associated with disease recurrence. This review addresses the critical issues regarding tumor-induced inflammation and its role in breast cancer progression focusing specifically on the changes in HA metabolism within tumor reactive stroma as a key factor in malignant progression.

Nitrite attenuated hypochlorous acid-mediated heme degradation in hemoglobin

Hypochlorous acid (HOCl) is elevated in many inflammatory diseases and causes the accumulation of free iron. Through the Fenton reaction, free iron has the ability to generate free radicals and subsequently is toxic. Recent studies have demonstrated that HOCl participates in heme destruction of hemoglobin (Hb) and free iron release. In this study, it was showed that nitrite (NO2−) could prevent HOCl-mediated Hb heme destruction and free iron release. Also, NO2− prevented HOCl-mediated loss of Hb peroxidase activity. After the NO2−/HOCl treatment, Tyr 42 in α-chain was found to be nitrated in Hb, attenuating the electron transferring abilities of phenolic compounds. The protective effects of NO2− on HOCl-induced heme destruction were attributed to its reduction of ferryl Hb and/or direct scavenging of HOCl. Therefore, NO2− could show protective effects in some inflammatory diseases by preventing HOCl-mediated heme destruction of hemoproteins and free iron release.

Elastic properties of hydrate-bearing sandy sediment during CH4–CO2 replacement

CH4–CO2 replacement method can not only recover methane from natural gas hydrate, but also implement CO2 geological sequestration. The effect of CH4–CO2 replacement with gaseous or liquid CO2 from natural gas hydrates, and the stiffness evolution during the stages of CH4 hydrate formation, free methane gas release, gaseous or liquid CO2 flooding, and CH4–CO2 replacement were experimentally investigated by in situ measuring the compressional wave velocity of hydrate-bearing sediments. The measured results showed that the P-wave velocity and amplitude of the hydrate-bearing sediments behave in the same way and decrease slightly because of the dissociation of CH4 hydrate when free CH4 gas was released and CO2 gas was injected. At the stage of CH4–CO2 replacement, methane hydrate may be coated by newly-formed hydrate which prevents CH4 or CO2 molecules passing through. Both the P-wave velocity and the amplitude gradually decrease with the increase of replacement percentage owing to the different properties between CH4 hydrate and CO2 hydrate. The elastic modulus of hydrate-bearing sediments was found to decrease with the dissociation of CH4 hydrate and the formation of CO2 hydrate, indicating the CH4–CO2 replacement may weaken the rigidity of the sediment skeleton. However, the fluctuation of bulk stiffness is at a low level and the stiffness of hydrate-bearing sediments can still be maintained.

Nitric oxide-releasing polymeric nanoparticles against Trypanosoma cruzi

Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite, Trypanosoma cruzi (T. cruzi), and the disease remains a major health problem in many Latin American countries. Several papers report that the killing of the parasite is dependent on the production of nitric oxide (NO). The endogenous free radical NO is an important cellular signalling molecule that plays a key role in the defense against pathogens, including T. cruzi. As T. cruzi is able to compromise host macrophages decreasing endogenous NO production, the administration of exogenous NO donors represents an interesting strategy to combat Chagas disease. Thus, the aims of this study were to prepare and evaluate the antimicrobial activity of NO-releasing polymeric nanoparticles against T. cruzi. Biocompatible polymeric nanoparticles composed of chitosan/sodium tripolyphosphate(TPP) were prepared and used to encapsulate mercaptosuccinic acid (MSA), which is a thiol-containing molecule. Nitrosation of free thiols (SH) groups of MSA were performed by the addition of equimolar amount of sodium nitrite (NaNO2), leading to the formation of S-nitroso-MSA-containing nanoparticles. These polymeric nanoparticles act as spontaneous NO donors, with free NO release. The results show the formation of nanoparticles with average hydrodynamic diameter ranging from 270 to 500 nm, average of polydispersity index of 0.35, and encapsulation efficiency in the range of 99%. The NO release kinetics from the S-nitroso-MSA-containing nanoparticles showed sustained and controlled NO release over several hours. The microbicidal activity of S-nitroso-MSA-containing nanoparticles was evaluated by incubating NO-releasing nanoparticles (200 - 600 μg/mL) with replicative and non-infective epimastigote, and non-replicative and infective trypomastigote forms of T. cruzi. In addition, a significant decrease in the percentage of macrophage-infected (with amastigotes) and NO-releasing nanoparticle-treated cells was observed. Taken together, our results reveal a potent toxic effect of NO-releasing polymeric nanoparticles against different life cycle forms of T. cruzi, indicating that the encapsulation of the NO donor S-nitroso-MSA represents an interesting approach to combat and to prevent Chagas disease.

A green method for polybutylene succinate recycling: Depolymerization catalyzed by lipase B from Candida antarctica during reactive extrusion

This study aims to investigate a “green” recycling route for polybutylene succinate (PBS) based on reactive extrusion in the presence of an enzyme catalyzing the hydrolysis of this aliphatic polyester: lipase B from Candida antarctica. This enzyme was chosen due to its thermal stability, since reactive extrusion was performed at 120°C (i.e. above PBS melting temperature). PBS hydrolysis was measured after extrusion at 120°C either in a single or a twin screw extruder, in the presence of 0–10wt% C. antarctica lipase for 5 or 30min. In a twin screw extruder, the residual activity of the enzyme was still 38% or 24%, after 5–30min extrusion at 120°C, respectively. For instance, the weight average molecular weight (Mw) of PBS decreased from 82,000 to 4500gmol−1 after extrusion for 5min in the presence of 1% wt of lipase. The highest yield of free succinic acid release (44%) was obtained following a 30min extrusion in the presence of 10wt% of C. antarctica lipase. The drastic decrease in weight average molecular weight of PBS after enzymatic hydrolysis caused an only 10°C decrease in the melting temperature.

Expanding the scope of memory search: Modeling intralist and interlist effects in free recall.

The human memory system is remarkable in its capacity to focus its search on items learned in a given context. This capacity can be so precise that many leading models of human memory assume that only those items learned in the context of a recently studied list compete for recall. We sought to extend the explanatory scope of these models to include not only intralist phenomena, such as primacy and recency effects, but also interlist phenomena such as proactive and retroactive interference. Building on retrieved temporal context models of memory search (e.g., Polyn, Norman, & Kahana, 2009), we present a substantially revised theory in which memory accumulates across multiple experimental lists, and temporal context is used both to focus retrieval on a target list, and to censor retrieved information when its match to the current context indicates that it was learned in a nontarget list. We show how the resulting model can simultaneously account for a wide range of intralist and interlist phenomena, including the pattern of prior-list intrusions observed in free recall, build-up of and release from proactive interference, and the ability to selectively target retrieval of items on specific prior lists (Jang & Huber, 2008; Shiffrin, 1970). In a new experiment, we verify that subjects' error monitoring processes are consistent with those predicted by the model.

Free Actin Impairs Macrophage Bacterial Defense: Reversal by Plasma Gelsolin

Alveolar macrophage (AM) bacterial clearance is critical to host defense against lung infections. We sought to assess: 1) the effects of free‐actin released during lung injury on AM function and 2) the therapeutic potential of the actin‐binding protein plasma gelsolin (pGSN). AM binding and uptake of bacteria in the presence or absence of free actin and pGSN was measured in vitro using assays based on CFU quantitation or scanning cytometry and fluorescence microscopy of bacteria. We demonstrate impaired binding of Streptococcus pneumoniae by murine B6 AMs in the presence of free actin and reversal of impaired binding by pGSN. In contrast, albumin, heat‐denatured actin or vehicle control do not affect AM bacterial binding, thus establishing specificity. Similarly, primary human AM‐like macrophages also show impaired binding and uptake of Staphylococcus aureus in the presence of free actin or cytochalasin D and improved binding and uptake by pGSN. In conclusion, free actin was found to significantly impair AM binding and phagocytosis of microbial pathogens in vitro, an effect that was reversed in the presence of pGSN. The scanning cytometry method used in these studies will be useful to investigate the mechanism(s) by which free actin interferes with AM bacterial binding. Free actin release after lung injury may contribute to the risk of secondary bacterial pneumonia, and pGSN may offer a therapeutic strategy to reduce this risk.Funding provided by NIH HL007118

Commentary on: Antibody and B Cell Responses to Plasmodium Sporozoites.

Dups et al. (1) assess how antibody and B cell responses to Plasmodium sporozoites may function as protective immune responses. They cover immune induction quite extensively but discuss virtually nothing on effector mechanisms of antibody responses against sporozoites. Because their review should be balanced by reference to studies describing effector mechanisms, this commentary will confine itself to recounting some of these. In vitro exposure to serum from immunized mice results in an antibody-mediated precipitant projecting from sporozoites (2). Because of the striking way in which immune serum deformed sporozoites, this “CSP” reaction was postulated to be the basis for a humoral component of immunity against sporozoites. In vitro inhibition of sporozoite motility by serum from immune animals subsequently suggested that anti-sporozoite antibodies can function by blocking sporozoite motility (3). Further in vitro studies showed that monoclonal antibodies against the CS antigen blocked in vitro invasion by sporozoites into target cells (4, 5). Subsequent intravital studies revealed in vivo inhibition of sporozoite motility and inhibition of sporozoite invasion of dermal blood vessels by antibodies (6). And an association between high levels of CS antibodies and protection was shown in the first successful human immunization with radiation-attenuated sporozoites (7). Anti-sporozoite antibodies act even earlier during challenge by mosquito bite, by inhibiting release of sporozoites from the mosquito proboscis into skin (8). This appears to be the initial manifestation of functional immunity against pre-erythrocytic malaria parasites. Analysis of kinetics of Plasmodium berghei sporozoites injected by mosquitoes into sporozoite-immunized vs. non-immunized mice showed significantly fewer sporozoites were deposited in immune mice (8). CS protein is released by sporozoites into media in vitro (9) and into saliva within salivary glands of infected mosquitoes (10, 11). Thus, CS protein released into mosquito saliva together with sporozoites is injected into hosts while mosquitoes probe for blood meals. This mosquito-injected CS protein appears to interact with homologous anti-CSP antibodies within immunized hosts at sites of saliva release; the interaction produces immune complexes that interfere with free release of sporozoites by mosquitoes in vitro and in vivo (8). Some sporozoites injected by mosquitoes into immunized hosts may successfully escape into the blood. Indeed, sporozoites that bypass skin by being injected intravenously by syringe into mice passively immunized with immune serum are cleared effectively from the circulation (12), indicating a functional role for antibodies against “break-through” sporozoites that have reached the blood. Conceivably, antibody-coated sporozoites may be blocked during attempted passage through Kupffer cells prior to hepatocyte invasion (13, 14). In vitro studies have documented that opsonized sporozoites are prone to phagocytosis (15–17), suggesting that Kupffer cells can eliminate opsonized sporozoites in vivo. Furthermore, antibodies also inhibit invasion and traversal through hepatocytes, events that rely on sporozoite motility (18). Thus, anti-sporozoite antibodies can act sequentially against sporozoites at different stages of sporozoite invasion from the skin to invasion of dermal blood vessels, to passage from Kupffer cells into hepatocytes, and subsequent traversal of sporozoites through a series of hepatocytes.