Avidity Research Articles

The Effect of Ligand Mobility on the Cellular Interaction of Multivalent Nanoparticles.

Multivalent nanoparticle binding to cells can be of picomolar avidity making such interactions almost as intense as those seen with antibodies. However, reducing nanoparticle design exclusively to avidity optimization by the choice of ligand and its surface density does not sufficiently account for controlling and understanding cell-particle interactions. Cell uptake, for example, is of paramount significance for a plethora of biomedical applications and does not exclusively depend on the intensity of multivalency. In this study, it is shown that the mobility of ligands tethered to particle surfaces has a substantial impact on particle fate upon binding. Nanoparticles carrying angiotensin-II tethered to highly mobile 5 kDa long poly(ethylene glycol) (PEG) chains separated by ligand-free 2 kDa short PEG chains show a superior accumulation in angiotensin-II receptor type 1 positive cells. In contrast, when ligand mobility is constrained by densely packing the nanoparticle surface with 5 kDa PEG chains only, cell uptake decreases by 50%. Remarkably, irrespective of ligand mobility and density both particle types have similar EC50 values in the 1-3 × 10-9 m range. These findings demonstrate that ligand mobility on the nanoparticle corona is an indispensable attribute to be considered in particle design to achieve optimal cell uptake via multivalent interactions.

Associated Antenatal Health Risk Factors with Incidence of Toxoplasmosis in Egyptian Pregnant Women.

The major maternal toxoplasmosis infection during pregnancy is regularly related to trans-placental transmission to the embryo and newly-borne child. This cross-section study was performed to investigate the prevalence of toxoplasmosis among pregnant women attending antennal health centers. The IgM antibodies against Toxoplasma were quantitatively determined by commercially available kits, while IgG antibodies and avidity (AV) of Toxoplasma gondii-specific IgG antibodies were quantitatively determined by using of conventional ELISA. The overall seroprevalence of T. gondii IgM among the investigated pregnant women was much higher than toxoplasma IgG with low IgG avidity representing acute infection with possibility of risk to the mother, embryo and newly-borne child. Results also showed that highest Toxoplasma prevalence was among pregnant women with history of intake of immunosuppressive drugs and abortion, having cats and animals in their households and in the 1st and 2nd trimesters. The high infection prevalence of T. gondii among the Egyptian pregnant women in Giza governorate revealed the risk of premature termination of pregnancy due to exposure of T. gondii infection.

A pilot study on the biodistribution pattern of 68Ga-DOTA-TATE in normal organs of adults

Objective To retrospectively study the biodistribution of 68Ga-DOTA-TATE as a SSTR imaging agent in human subjects. Methods A total of 106 patients with suspected disease were enrolled in this study. All patients were histologically proven for having either a single tumor <2 cm or without evidence of tumor during follow-up. Patients underwent PET/CT whole-body scan 17-100 min after intravenous injection of 55.2-220.0 MBq 68Ga-DOTA-TATE. ROI was drawn for measuring SUV of tracer-avid pathologies. One-way analysis of variance and two-sample t test were used for statistical analysis. Results High 68Ga-DOTA-TATE avidity was found in pituitary, with SUVmax of 4.00±1.21. Tracer was excreted mainly through urinary system resulting in highest uptake in the urinary tracts. The SUVmax of kidney cortex was 19.01±5.45. Mediastinal blood pool and liver SUVmax were 0.93±0.33 and 7.69±2.26, respectively. Mild uptake of 68Ga-DOTA-TATE was found in the brain, cerebellum, lung and muscle, all lower than that of mediastinal blood pool. Moderate accumulation of 68Ga-DOTA-TATE (close to or slightly higher than liver) was found in adrenal gland and spleen, with SUVmax 7.61±3.42 and 8.63±2.31, respectively. Other organs (pituitary, salivary gland, thyroid, pancreas, small intestine, colon, uterus, prostate and bone) showed tracer uptake in the range between those of mediastinal blood pool and liver. 68Ga-DOTA-TATE distribution in pancreas was not uniform. Nine patients had focal accumulation in the uncinate process of pancreas with highest SUVmax up to 8.48. However, the SUVmax and SUVmean in the rest of pancreas (head, neck, body and tail) showed insignificant difference (F values: 0.703, 0.563, both P>0.05). 68Ga-DOTA-TATE uptake in each organ reached equilibrium quickly after injection but with slight increase over time. The changes in SUV, however, showed insignificant difference among organs, including different parts of pancreas (t values: from -0.09 to 1.75, from -1.70 to -0.42, respectively, all P>0.05). Conclusions The biodistribution of 68Ga-DOTA-TATE reaches equilibrium shortly after intravenous administration and is stably maintained. The biodistribution activities are organ-specific, and characteristic to that of SSTR concentration. Key words: Octreotide; Gallium radioisotopes; Positron-emission tomography; Tomography, X-ray computed

Quantitative comparison of 68Ga-NGR and 18F-FDG uptake in well-differentiated hepatocellular carcinoma bearing mice

Objective To quantitatively compare the diagnostic capability of 68Ga-NGR and 18F-FDG in well-differentiated hepatocellular carcinoma (HCC) bearing mice by microPET/CT imaging. Methods The in vitro cellular uptake, in vivo microPET/CT imaging and biodistribution studies of 68Ga-NGR and 18F-FDG were quantitatively compared in SMMC-7721-based well-differentiated HCC. The human fibrosarcoma (HT-1080) and human colorectal adenocarcinoma (HT-29) cells/xenografts were respectively used as positive and negative reference groups for CD13. The expression of CD13 was qualitatively verified by immunohistostaining. The levels of CD13 and glucose-6-phosphatase (G6Pase) were semi-quantitatively analyzed by Western blot test for all 3 types of tumors. Two-sample t test was used for data analysis. Results The in vitro cellular uptake showed that the 68Ga-NGR uptake in SMMC-7721 and HT-1080 cells was higher than that in HT-29 cells, and the 68Ga-NGR uptake was higher than 18F-FDG uptake in SMMC-7721 cells. The in vivo microPET/CT imaging results revealed that the uptake of 68Ga-NGR in SMMC-7721 tumor was (2.17±0.21) %ID/g, remarkably higher compared to (0.73±0.26) %ID/g of 18F-FDG uptake (t=8.826, P<0.01). The tumor/liver ratio of 68Ga-NGR was 2.05±0.16, which was 2.03-fold higher than that of 18F-FDG. In the HT-1080 tumors, the uptakes of 68Ga-NGR and 18F-FDG were both high, and the values were (2.46±0.23) %ID/g, (3.47±0.31) %ID/g. The uptake of 68Ga-NGR was significantly lower than that of 18F-FDG in HT-29 tumors: (0.67±0.20) %ID/g vs (3.17±0.29) %ID/g; t=4.221, P<0.01. Western blot and immunohistostaining results were as follows: HT-1080(CD13+ , G6Pase-), SMMC-7721(CD13+ , G6Pase+ ), HT-29(CD13-, G6Pase-). Conclusions The uptake of 68Ga-NGR is higher than 18F-FDG uptake in SMMC-7721 tumor bearing mice, therefore it is worthwhile to consider the feasibility of clinical translation for PET/CT in diagnosis of HCC. Furthermore, because of the difference in 68Ga-NGR and 18F-FDG avidities in tumors with different molecular phenotypes of CD13 and G6Pase, there is an underlying potential for molecular imaging in the determination of molecular phenotypes. Key words: Liver neoplasms; Positron-emission tomography; Tomography, X-ray computed; Gallium radioisotopes; Asparagine-glycine-arginine; Deoxyglucose; Mice, nude

A novel role for Cish in the inhibition of TCR signaling

Cancer immunotherapeutics focus primarily on stimulating the immune system to elicit endogenous immune responses to fight cancer or transferring primed immune effectors in adoptive cell transfer (ACT) paradigms (1,2). CD8 + T cells are desirable immune effectors in cancer, however, their antitumor activity is often attenuated by tolerance mechanisms or the suppressive nature of the tumor microenvironment (3). As such, the goal of cancer immunotherapies is increasingly focusing on overcoming the tumor tolerance barrier by enhancing the antigen reactivity and effector function of tumor-specific T cells (4), however, the presence of T cells with high-affinity for their cognate antigen is often precluded by thymic selection (5,6). Therefore, developing methods of enhancing T cell receptor (TCR) signaling or functional avidity to maximize antitumor efficacy of tumor-specific T cells (7) can improve cancer therapies employing ACT, vaccines, or checkpoint inhibitors. Current approaches include the development of affinity-enhanced antigen receptors for ACT therapies, but these have been met with challenges (8,9), including treatment-related toxicities (10-12). In an effort to identify new druggable targets to increase CD8+ T cell functional avidity for tumor-specific antigens and increase tumor killing, Palmer et al . identified a novel intrinsic pathway inhibiting TCR signaling cascades and limiting CD8+ T cell activity in murine tumors (13).

Preliminary analysis of distribution and effect on IgG avidity and subclass of anti double-stranded DNA antibody in lupus nephritis

Objective The aim of this study was to estimate the distribution and effect of anti dsDNA antibody on avidity and IgG subclass in lupus nephritis (LN). Methods Case control study. A total of 148 patients first diagnosed as LN was enrolled from February 2012 to May 2014. 91 patients in renal department received renal biopsy. The avidity as well as IgG subclass of anti dsDNA antibody in serum were detected by ELISA. Renal involvements were classified according to the pathological results. The disease activity, including white blood cell count, urinary red blood cell count, urinary protein, serum creatinine, C3, SLEDAI score, and pathology activity index (AI), chronicity index (CI) was recorded. The relationship between activity and avidity as well as IgG subclass was assessed by Spearman correlation. Results Avidity index of anti-dsDNA IgG antibody in LN patients was 33.7 (19.2-51.1). It was higher in IIF positive group than in IIF negative group (H=15.13, P=0.0001). Anti-dsDNA IgG3 (24 cases, 26.4%) was the predominant subclass, followed by all of four subclasses positive (10 cases, 11.0%). Anti-dsDNA antibody avidity was not associated with any indicator. IgG3 subclass was correlated with AI negatively (R=-0.42, P=0.03). Conclusions IgG avidity of anti-dsDNA antibody was not related with renal involvement. IgG3 is the main subclass of LN patients and associated with pathology AI. IgG3 can be used as an indirect indicator of renal involvement in LN. (Chin J Lab Med, 2015, 38: 809-812) Key words: Lupus nephritis; Immunoglobulin G; Antibody affinity; DNA

The humoral immune response in guinea pigs primed with recombinant vaccinia virus strains expressing Transmitted/Founder virus HIV-1 membrane proteins and boosted with gp140 protein

Objective To analyze the antibody responses in guinea pigs vaccinated with recombinant vaccinia virus(rTT) strains expressing transmitted/founder (T/F) HIV-1 membrane proteins in combination with gp140 protein. Methods Guinea pigs were primed with rTT strains and boosted twice with gp140 protein in every four weeks. Serum samples were collected from guinea pigs before immunization and in 2, 6 and 10 weeks after the last immunization for the detection of HIV-1-specific binding antibodies, neutralizing antibodies and the relative avidity of antibodies. Results (1) The binding antibodies specific to HIV-1 B′/C, B, AE subtypes were efficiently induced by the immunization of rTT-B, rTT-C and rTT-CON vaccinia strains in combination with gp140 protein. The antibody titers ranged from 111 430 to 1 024 000. More antibodies against HIV-1 B′/C and AE subtypes were induced in guinea pigs by the immunization of rTT-C and rTT-CON strains in combination with gp140 protein than those by using rTT-B strain prime-protein boost strategy (P<0.05). No significant differences with the titers of HIV-1 B subtype specific antibody were observed among the guinea pigs immunized with the three strategies. (2) High titers of SF162 and ZM109 neutralizing antibodies were induced in guinea pigs immunized with rTT-B, rTT-C and rTT-CON vaccinia strains in combination with gp140 protein, ranging from 83.76 to 649.30. No significant differences were found among the three groups. (3) The HIV-1 V1V2-gp70 specific antibodies associated with protective immunity were induced by immunization of the three virus prime-protein boost strategies. No significant differences were observed among them. (4) Antibodies induced in guinea pigs by immunization of the three strategies showed strong affinity to membrane proteins of HIV-1 B′/C, B, AE subtype strains. No significant differences were found among the three immunization strategies. Conclusion A strong humoral immune response was induced in guinea pigs primed with recombinant vaccinia virus strains expressing T/F virus HIV-1 membrane proteins and boosted with gp140 protein. Key words: HIV; Transmitted/founder virus; Recombinant vaccinia virus; Protein vaccine; Combined immunization

Pigmented Villonodular Synovitis Masquerading as Metastasis on PET Imaging

Pigmented villonodular synovitis (PVNS) is a metaplastic process that can occur in the synovium, bursae or tendon sheaths and can be localized or diffuse. Its features on radiographs and computed tomography are nonspecific, but magnetic resonance imaging is diagnostic. Its appearance on fluorodeoxyglucose (FDG) positron emission tomography (PET) is not well described. We present a case of recurrent squamous cell carcinoma of the floor of the mouth with an FDG-avid lesion of the left upper arm on a whole-body PET scan that was shown to be PVNS on subsequent biopsy. To our knowledge, this is one of the very few cases reported in the literature describing FDG avidity of PVNS. We explore the features of PVNS on various imaging modalities and its potential for being mistaken for malignancy. J Med Cases. 2014;5(4):253-255 doi: http://dx.doi.org/10.14740/jmc1691w

Seroprevalence of Cytomegalovirus infection in children aged 0-8 years in Nanjing

Objective To investigate the seroprevalence of Cytomegalovirus (CMV) infection and ages of the children in primary for better understanding the status of CMV infection in China with evidence-based medicine. Methods Total 837 children randomly selected from Nanjing Children's Hospital, from Jun.to Sep.in 2011, including 513 boys and 324 girls, aged from 1 day to 8 years, with mean age of 3.6 years old , were recruited.Serum samples were tested for CMV IgM, CMV IgG, and CMV IgG avidity index using commercial enzyme-linked immunosorbent assay kits. Results Of the total serum samples from 837 children, 690 cases were CMV IgG positive.The overall seroprevalence of CMV IgG was 82.4%, with 83.2% (427/513 cases) and 81.2% (263/324 cases) in boys and girls, respectively.There was no significant difference in the seroprevalence of CMV IgG between boys and girls (χ2=0.584, P=0.445). Of the 92 infants less than 6 months old, 86 cases were CMV IgG positive, and the positive rate was 93.5%.The prevalence gradually declined in infants after 7 months old, fell to the lowest level of 66.7% at age of 9 months, and then constantly maintained around 80.0% from 1 to 8 years old (χ2=15.4, P<0.001). CMV IgM in 352 serum samples were tested, and 23 (6.5%) cases were CMV IgM positive.The positive rate peaked in infants at age of 2-3 months (7/12 cases, 58.3%), then decreased over the age and none of the children older than 6 years were IgM positive (χ2=5.1, P<0.001). Furthermore, the CMV IgG avidity index assay was performed in all 23 cases of IgM positive indivi-duals to estimate the primary CMV infection rate.The results showed low avidity index (<30%) in 13 infants, the primary infection rate was 56.5% (13/23 cases). Most subjects with primary infection (n=7, 53.8%) were younger than 1 year old. Conclusions The current seroprevalence of CMV IgG in children in China was around 80.0%, lower than that in adults, and the primary CMV infection mostly occurred before 3 months of age. Key words: Cytomegalovirus; Seroprevalence; Primary infection; Child

VALIDATION OF NEUROTENSIN TETRA-BRANCHED PEPTIDES AS TUMOR TARGETING AGENTS IN PANCREAS, COLON AND BLADDER CARCINOMA

The identification of new tumor targeting agents, which might allow either cancer cell tracing or ther- apy, is a crucial issue in cancer research. Membrane receptors for endogenous peptides such as neu- rotensin, somatostatin, bombesin and many others are over-expressed in different human cancers and could therefore be targeted as tumor-specific antigens. In the meantime the extremely short half-life of pep- tides impeded their development for effective pep- tide-based tumor targeting strategies. We synthesized tetra-branched neurotensin peptides (NT4), which ensure extremely long half-life main- taining peptide specificity and increasing avidity through multimeric binding. Moreover this bio-syn- thetical strategy allows a considerable modularity of peptides through the conjugation of different func- tional unit, such as fluorophore, radioactive moieties or chemotherapeutic drugs. Aim of our studies is to validate NT4 for cancer cell tracing in different human tumors. In this view we use fluorophore-conjugated NT4 to discriminate be- tween tumor and healthy tissue obtained by surgical samples from pancreas, colon and bladder carcinoma. Peptide binding on tumor and healthy biopsies was measured in each patient by quantitative analysis of confocal microscopy images. These results show a considerable difference in fluorescence emission be- tween healthy and tumor samples in colon, pancreas and bladder cancer, opening the way to the develop- ment of NT4 as selective diagnostic tools for these pathologies. Moreover our peptides can be conju- gated with different chemotherapeutic moieties in order to allow the selective killing of tumor cells.

Acetylating for avidity

Acetylating for avidity

The effect of the human cytomegalovirus pp65 IgG-avidity index for the human cytomegalovirus primary infection in mice model

Objective To investigate the significance of human cyomeg Movirus(HCMV)pp65 IgG antibody avidity index(AI)for the clinical diagnosis of HCMV primary infection through the experimental model of HCMV primaly infection in BALB/c mice.Methods 6～8 weeks,female,specific-pathogen-free BALB/c mice were divided into 5 groups.6 mice in each group. And he mice were injected with 2×106 PFU/m1,2×105 PFU/mi,2×104 PFU/ml,2×103 PFU/ml and 2×102 PFU/ml of HCMV intraperitoneally respectively. Another 6 mice were injected intraperitoneally with the maximum dose of HCMV kept at 56℃ for 30 min as inactivated virus group.And HF negative control group was established at same time. All the mice ere sacrificed to obtain brain and lung tissues for the following experiments after 1 montll.(1)Tissue samples obtained from mice were inoculated in human embryo fibroblasts(HF)monolayers after routine treatment for virus isolation.HCMV specific eytopathie effect(CPE) was observed bv inverted phase-contrast microscopy.HCMV UL83 DNA in the ultures as tested by PCR and pp65 antigen was detected by indirect immunofluorescence.(2)Extracted mRNA from tissue samples and HCMV pp67 mRNA were analyzed by reverse transcriptase PCR(RT-PcR).(3)Immunoglobulin M(IgM)antibody and immunoglobulin G(1gG)antibody avidity Was investigated for their usefulness in distinguishing primary genital HCMV infections rom nonprimary infections with ELISA kit using truncated pp65 protein.ResultsHCMV can be isolated in the tissues from the mice injected with 2×106 PFU/ml and 2×105 PFU/m1.RT- PCR and ELISA showed positive results in the same groups.The infective rates were 100%.The analysis of the low doses groups,inactivated group and HF negative ontrol group all showed negative results.Conclusions BALB/c mice can be infected with HCMV and appeared as primary infection after1 month.Determination of HCMV pp65 IgM and HCMV p065 IgG-AI by ELISA incorporated with virus isolation and RT-PCR are helpful for distinguishing primary infections from nonpfimary infections.The detection of HCMV p65 IgM and HCMV pp65 IgG-AI by ELISA utilizing recombinant protein pp5 as antigens can be used for preliminary screening. Key words: Cytomegalovirus infections; Disease models,animal; PhosphoproteinsImmunoglobuli G; Antibody affinity; Enzyme-linked immunosorbent assay

Avidity of anti-glomerular basement membrane autoantibodies was associated with renal pathological damage

To investigate the avidity of anti-glomerular basement membrane (GBM) antibodies and their association with clinical and pathological parameters of patients with anti-GBM disease. Sera from 52 patients and serial samples from 11 patients with anti-GBM disease, diagnosed in our hospital in the last 11 years, were collected. Purified bovine alpha chain non-collagen 1 domains of type IV collagen [alpha(IV)NC1] was employed to exam avidity of anti-GBM antibodies using antigen-inhibition enzyme-linked immunosorbent assay (ELISA). The amount of alpha(IV)NC1 needed for 50% inhibition of antibody binding was compared between patients with different clinical and pathological manifestations. After the sera were diluted to give the same absorbance, the amount of alpha(IV)NC1 used was different among different patients, with an average at 0.625 microg (0.02-20 microg). A significant correlation was observed between the amount of alpha(IV)NC1 used and the percentage of glomerular crescents (P = 0.001). Higher avidity of anti-GBM antibodies predicted a higher percentage of glomerular crescents (R(2) = 0.58, P = 0.000). No correlation was observed between avidity and age, gender, interval between onset and diagnosis and other clinical data. No changing avidity was observed in serial samples with time. Affinity maturation might have been completed by the time that patients presented with anti-GBM disease. The different avidity of anti-GBM antibodies was associated with the degree of renal damage and might play a key role in the pathogenesis of anti-GBM disease.

Inhibitory effects of OK-432 (Picibanil) on cellular proliferation and adhesive capacity of breast carcinoma cells.

We investigated the potent inhibitory effects of OK-432 (Picibanil) on both cellular adhesion and cell proliferation of estrogen-dependent (MCF-7) or estrogen-independent (MDA-MB-231) breast carcinoma cells. Cellular proliferation of both MCF-7 and MDA-MB-231 cells was markedly inhibited in a dose-dependent manner, when the carcinoma cells were exposed to OK-432. Cell attachment assay demonstrated that incubation with OK-432 for 24 h reduced integrin-mediated cellular adhesion of both cell types. However, fluorescence activated cell sorter (FACS) analysis revealed that incubation with OK-432 for 24 h did not decrease the cell surface expressions of any integrins. These results suggest that the binding avidity of integrins is reduced by OK-432 without alteration of the integrin expression. We conclude that OK-432 inhibits integrin-mediated cellular adhesion as well as cell proliferation of breast carcinoma cells regardless of estrogen-dependence, and that these actions of OK-432 contribute to prevention or inhibition of breast carcinoma invasion and metastasis.

Does physiology regulate our avidity for salt?

Does physiology regulate our avidity for salt?

Avidity of Radiogallium for Bone in Thalassemia

Avidity of Radiogallium for Bone in Thalassemia

Studies of membrane receptors, phagocytosis, and morphology of subpopulations of rat lung interstitial macrophages.

Recent data suggest that pulmonary macrophages may be heterogeneous. Several studies have demonstrated that alveolar macrophages are functionally and biochemically heterogeneous. In addition, interstitial macrophages, which are believed to be the precursors to alveolar macrophages, have been suggested to be heterogeneous. Therefore, this study was undertaken to determine if density-defined interstitial macrophages (DD-IM) are heterogeneous with respect to receptors for zymosan, immunoglobulin, and complement as well as morphologically. Furthermore, avidity for IgG was defined by opsonizing sheep red blood cells (SRBC) with different amounts of IgG. Interstitial macrophages were harvested and separated into 18 DD-IM subpopulations by centrifugation through a continuous iso-osmotic gradient of colloidal silica. Interstitial macrophages showed marked heterogeneity in cellular volume. Furthermore, macrophages of density 1.046 to 1.075 g/ml exhibited higher receptor activity capability of attaching and phagocytizing SRBC opsonized with small amounts of IgG and towards zymosan. All DD-IM exhibited similar abilities to attach complement-coated SRBC. These results demonstrate the functional heterogeneity of interstitial macrophages with respect to IgG and zymosan.

Production and Evaluation of Antibodies for Radioimmunoassay of Secretin

In order to produce antibodies for radioimmunochemical analysis of secretin in plasma, 16 rabbits were immunized; two different immunization schemes were followed. All rabbits produced detectable antibodies to secretin. The final dilution of the antisera necessary to bind 50% of 5 fmol [125I]secretin varied from 1:5,000 to 1:2,300,000. The avidity of antisera, expressed by the equilibrium constant, ranged from 5 x 10(6) 1 x mol-1 to 3 x 10(11) 1 x mol-1. Six rabbits produced antisera that displayed avidity sufficient for measurement of the physiologic concentrations of secretin in plasma (Keff greater than 10(11) 1 x mol-1). The equation of Sips was used to evaluate the heterogeneity of the antibodies. Seven of the 16 antibodies to secretin had a heterogeneity index of 0.90 or more. Cross-reactivity with structurally related peptide hormones (glucagon, vasoactive intestinal peptide, gastric inhibitory peptide) was found to be negligible for the six antisera examined (those with the highest avidity). Three of the high-avidity antisera were examined for reactivity with secretin fragments. They all bound the C-terminal secretin tricosa and tetradecapeptides almost as well as pure natural secretin, whereas the reactivity with the N-terminal tetradecapeptide was slightly lower.

Chagas' disease and trypanosomiasis rangeli in 3 ranchs of the Departmento Francisco Morazán, Honduras

Observations in three Rhodnius prolixus infected thatch-roofed huts in the Departamento Francisco Morazan, Honduras, revealed that of their 22 inhabitants, 11 were positive serologically for Chagas’ disease, four of them with the Romana sign, and positive Trypanosoma cruzi hemoculture and xenodiagnosis. Another five persons (two serologically positive for Chagas' disease) were positive only for Trypanosoma rangeli in hemoculture, two of which were also positive for the same parasite by xenodiagnosis. Pure and mixed infections by both trypanosomes were found in 1230 R. prolixus captured in the three huts. In T. rangeli , examination of the feces, hemolymph and salivary glands is necessary to determine the number of infected insects. Precipitin tests showed the avidity of R. prolixus for biting man; one insect was found positive for human and opossum blood concomitantly.

THE CROSS-REACTIVITY OF LYMPHOCYTE AND RED CELL ANTIBODIES.

Abstract This study, stimulated by the observation that in chronic lymphocytic leukemia both lymphocytes and red cells may be coated with antibody globulins reactive with Coombs antiserum, defined the presence of common red cell and lymphocyte cellular antigens by demonstrating that their experimentally induced antibodies are cross-reactive. This was done by immunizing rabbits with separate antigens and, with appropriate agglutinations and absorptions, quantitating homologous (concordant) and heterologous (discordant) antibody reactivities. Finer details of these antibodies were delineated by sensitizing lymphocytes with matched and mismatched antisera, subsequently incubating them with red cells, and evaluating these reactants for mixed lymphocyte-red cell agglutination and separate red cell clumping. In addition, dissociation of nonagglutinating lymphocyte antibody from the lymphocyte and reassociation on the red cell were tested by the mixed agglutination technique in combination with rat anti-rabbit globulin. The composite findings suggested that both cellular elements share antigens with like structural groupings but that lymphocyte antibody has a greater avidity for the red cell than red cell antibody has for the lymphocyte. This experimental antibody partitioning, also observed clinically, suggests that the lymphocyte may be coated prior to the red cell in the Coombs-positive hemolytic anemia of chronic lymphocytic leukemia and that the current autoantibody concept of this type of anemia might be reappraised on this account.