Complement-dependent synergistic effects of rat monoclonal IgG antibodies in vivo

We describe studies aimed at maximizing the effector mechanisms responsible for eliminating target erythrocytes from the circulation in a fully homologous opsonization system in vivo. The effects on the subsequent fate of target erythrocytes were examined in both normal and decomplemented rats preinjected with a variety of rat IgG monoclonal antibodies (mAb) directed against different epitopes on the RTlA^a, the classical class I major histocompatibiliy complex antigen of the DA rat. In general, the clearance of both DA and (DA × PVG)F₁ erythrocytes in normal rats preinjected with various pairs of noncompetitive mAb was very rapid when compared with the overall clearance patterns seen with individual antibodies. With all mAb combinations containing IgG2b or IgG2a, an intact complement system was an essential requirement for augmenting the initial clearance and promoting hepatic sequestration of these target cells. The removal of (DA × PVG)F₁ erythrocytes, expressing half as much antigen, was considerably slower than the DA cells for each antibody pair tested although a notable degree of heterogeneity was observed in the overall behavior of both types of target cells with different mAb combinations. Our results suggest that the limiting effects of low antigen density on the target cells combined with the use of mAb of an isotype like the rat IgG2a can be overcome using pairs of mAb that recognize different epitopes on the same target antigen.     

Optimal field splitting for large intensity-modulated fields

The multileaf travel range limitations on some linear accelerators require the splitting of a large intensity-modulated field into two or more adjacent abutting intensity-modulated subfields. The abutting subfields are then delivered as separate treatment fields. This workaround not only increases the treatment delivery time but it also increases the total monitor units (MU) delivered to the patient for a given prescribed dose. It is imperative that the cumulative intensity map of the subfields is exactly the same as the intensity map of the large field generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. In this work, we describe field splitting algorithms that split a large intensity-modulated field into two or more intensity-modulated subfields with and without feathering, with optimal MU efficiency while satisfying the hardware constraints. Compared to a field splitting technique (without feathering) used in a commercial planning system, our field splitting algorithm (without feathering) shows a decrease in total MU of up to 26% on clinical cases and up to 63% on synthetic cases.     

Immunophenotypic changes and clinical outcome in B-cell lymphomas treated with rituximab.

Rituximab is a chimeric monoclonal antibody that recognizes the CD20 antigen and is used to treat B-cell non-Hodgkin lymphoma (B-NHL). Few studies have been published examining the use of antibody panels to evaluate B-NHL treated with rituximab. The authors performed a retrospective analysis of immunophenotypic changes and clinical outcome in 18 patients with B-NHL following rituximab therapy. The intensity of CD20 expression was evaluated by flow cytometry and/or immunohistochemistry, before and after rituximab therapy; the latter samples were taken 5 to 12 months after initiating rituximab therapy (median 7 months). Nine of the 18 patients (50%) achieved complete or partial clinical remission and did not have morphologic evidence of lymphoma in the post-therapy samples. The other nine patients (50%) had persistent disease. Two patterns of CD20 expression were noted in the post-therapy samples: unchanged expression of CD20 in neoplastic cells (4/9 cases) and loss of or a significant decrease in detected CD20 expression in neoplastic cells (5/9 cases). These results show that in many cases of B-NHL persisting after rituximab therapy, CD20 expression decreases or is lost, raising the possibility of deletion or expression modulation of the CD20 gene in neoplastic cells. This study also underscores the importance of using a panel of antibodies to evaluate rituximab-treated B-NHL.     

Effect of glass composition on the degradation properties and ion release characteristics of phosphate glass--polycaprolactone composites

A series of polycaprolactone and ternary-based (Na(2)O)(0.55-x)(CaO)(x)(P(2)O(5))(0.45) glass composites were created, each containing 20% volume percentage of glass with various calcium compositions. A short-term degradation study was carried out to investigate the physical and ion release behaviour of these composites, utilising analytical techniques such as dynamical mechanical analysis, and ion chromatography. All the composites experienced significant loss of weight and stiffness throughout the study, with the 24 mol% calcium composites losing the greatest amount of weight and stiffness. The pH profile of the aqueous solutions in which the composites were placed were initially acidic, but began to neutralise mid-way through the study, with the 36 mol% solution achieving the most acidic conditions. The ion release behaviour mirrored the mass loss behaviour of the glass component of the composites. The cations (sodium and calcium ions) release was comparable with the initial stages of composite mass degradation, both of which exhibited almost immediate release when placed into solution. The 24 mol% composites underwent rapid rates of cation release, while the 36 mol% experienced the slowest rates of release. By contrast, anion (phosphates and polyphosphates) release showed a dissimilar trend, with rapid release of the P(2)O(7) and P(3)O(10) occurring during the first few hours in solution, whilst the P(3)O(9) structure released steadily during the first 48 h in solution. Finally, PO(4) release was at a constant rate over the duration of the study, releasing up to 300 ppm from the 32 and 36 mol% samples by the end of 200 h. To summarise, these results show that by combining phosphate glasses with biodegradable polymer, it is possible to create composites whose rate of degradation can be controlled to meet the needs of their end application.     

Susceptibility and amplification of sensitivity in contact dermatitis.

We have examined the hypothesis that people who develop contact allergies to environmental substances do so because they have heightened susceptibility. Analysis of data from 2200 consecutive patients tested with the 20 commonest antigens in a patch-test clinic showed that more people developed multiple contact allergies than would be predicted from the frequency of single allergies; the excess was too great to be explained by chance and increased with number and rarity of the combinations of sensitizers. The possibility that this was due to enhanced individual susceptibility to sensitization rather than concomitant exposure to several sensitizers was confirmed by showing that patients with multiple allergies are more readily sensitized experimentally, and to a greater degree than normal, by dinitrochlorobenzene (DNCB), an unrelated antigen. The defect involves induction rather than expression of sensitivity. Amplification of the response to DNCB is proportional to susceptibility (calculated from the ratio of observed prevalence of multiple allergies to that predicted from the prevalence of single allergies) throughout the range from normal subjects, through those with a single sensitivity, to those with rare, multiple allergies. Therefore, we conclude that individual susceptibility is an important factor in the development of contact dermatitis, and occurs by a non-antigen-specific amplification of immune sensitization.     

Phenotypic characteristics, fatty acid composition, and isoprenoid quinone content of CDC group IIg bacteria.

Eleven strains of eugonic, nonoxidative, gram-negative rods isolated from clinical specimens formed a distinct group that was designated CDC group IIg. Five of the 11 isolates were from wounds. The phenotypic characteristics of CDC group IIg were most similar to those of Weeksella species, with the major difference being that CDC group IIg strains grew on MacConkey agar in 1 to 2 days, did not hydrolyze gelatin, and did not produce urease. All 11 strains of CDC group IIg possessed a distinct fatty acid profile that was characterized by large amounts (19 to 29%) of 18:1 omega 7c, 16:0, and 16:1 omega 7c, moderate amounts (6 to 10%) of 3-OH-14:0 and 14:0, and smaller amounts (1 to 2%) of 18:2, 18:0, and 3-OH-16:0. This fatty acid profile differs from those of Weeksella species by the absence of branched-chain fatty acids. CDC group IIg contains ubiquinone-8, as opposed to menaquinone-6 in Weeksella species. The isolates were susceptible to a variety of antimicrobial agents, including the aminoglycosides, tetracyclines, quinolones, sulfonamides, and polymyxin B.     

Role of a conserved amino-terminal sequence in the ecotropic MLV receptor mCAT1

The amino-terminus of mCAT1 and homologous proteins is predicted to form a positively charged, amphipathic alpha helix on the cytoplasmic side of the plasma membrane. Peptides with similar sequence motifs often provide membrane anchors, protein-protein interaction domains, or intracellular transport-targeting signals. Deleting most of the cytoplasmic N-terminal sequence of mCAT1 led to reduced expression on the cell surface and accumulation in the endoplasmic reticulum but did not abrogate receptor function. Surprisingly, when the N-terminal 36 or 18 amino acids of mCAT1 were fused to green fluorescent protein (gfp), gfp accumulated almost exclusively in mitochondria. Mitochondrial targeting depended on arginines at positions 15 and 16 and was inhibitable by downstream transmembrane sequences. Although the full-length mCAT1 was not detected in mitochondria, the mitochondrial-targeting property of the N-terminal sequence fused to gfp is conserved in orthologous and paralogous proteins that diverged approximately 80 million years ago, suggesting a conserved biological function. We propose that the conserved N-terminal motif of CAT proteins provides a regulatable signal for transport to, or retention in, different cell membrane compartments.