Preparation of long-circulating immunoliposomes containing adriamycin by a novel method to coat immunoliposomes with poly(ethylene glycol)

Modifications of liposomes with poly (ethylene glycol) (PEG) have been reported to prolong blood circulation time of liposomes. In this report, an adriamycin-encapsulated immunoliposomes were modified with PEG by two different approaches: one is the pre-coating method using lipid derivative of PEG as described by Allen et al. The other is post-coating method which is presented here. The former pre-coating method did not allow coupling of antibody due to the steric hindrance of PEG which had been introduced on liposome surface. On the other hand, in the later post-coating method, PEG-succinylcysteine was synthesized and was successfully conjugated with immunoliposomes via maleimido linker. Resultant PEG-coated immunoliposomes containing adriamycin retained their binding activity and cytotoxicity to target cells, and also showed significantly prolonged blood circulating time as compared with conventional immunoliposomes. This is a novel method to coat immunoliposomes with PEG.

Differential effects of 3 dipyridyl isomers on hepatic microsomal cytochrome P450 and heme oxygenase in rats

We compared the effects of 3 dipyridyl isomers, 2,2'-dipyridyl, 2,4'-dipyridyl and 4,4'-dipyridyl, on hepatic microsomal heme oxygenase and drug-metabolizing enzyme activities in male rats. 2,2'-Dipyridyl increased cytochrome P450 (P450) content at lower doses, but decreased with increasing dose levels. Immunoblot analysis revealed that 2,2'-dipyridyl did not induce both P450 1A1/2 and P450 2B1/2, in contrast to 2,4'- and 4,4'-dipyridyls, both of which were inducers of either P450 1A1/2 and/or P450 2B1/2. Some drug-metabolizing enzyme activities gradually declined with the increasing dose level of 2,2'-dipyridyl. 2,2'-Dipyridyl was able to induce hepatic microsomal heme oxygenase in a dose-dependent manner, but 2,4'- and 4,4'-dipyridyls did not, even at the highest dose (0.80 mmol/kg) examined. Treatment of rats with 2,2'-dipyridyl resulted in the increase of glutathione (GSH) content in a dose-dependent manner, but not 4-substituted isomers. A time course study with 2,2'-dipyridyl revealed that it produced a significant decrease in hepatic GSH content at early time periods (2-6 h) after its administration with an inverse increase in heme oxygenase activity. The present investigation has revealed that in contrast to the induction of P450 by 4-substituted dipyridyl compounds, 2,2'-dipyridyl is a novel inducer of hepatic microsomal heme oxygenase, together with the change in hepatic GSH content. This study would provide information on the differential effects of simple dipyridyl isomers on hepatic enzymes involved in heme and drug metabolism.

Characterization of cell surface antigens expressed in the HMA-1 breast cancer cell line

This report describes the characterization of an estrogen receptor-positive breast cancer cell line, HMA-1, established from a breast cancer patient, based on the expression of tumor-associated antigens (TAAs), the HLA-DR antigen, and the c-erbB-2 proto-oncogene product. In flow cytometric and immunohistochemical analyses, HMA-1 was found to express increased levels of several TAAs including MUC1, TAG-72 (sialyl Tn), Tn, T, sialyl Le(a), Le(x), and Le(y). HMA-1 also expressed enhanced levels of the HLA-DR antigen and c-erbB-2 protein. These results indicate that HMA-1 is a unique cell line with abundant TAAs which may serve as an appropriate breast cancer cell line for application in the multidisciplinary research of breast cancer.

Endocytosis does not necessarily augment the cytotoxicity of adriamycin encapsulated in immunoliposomes

We studied the relationship between endocytosis and cytoxicity of adriamycin (ADM) encapsulated in antibody-coated liposomes (immunoliposomes, IL) which are called chemoimmunoliposomes (CIL), by using several human cancer cell lines. IL coated with a monoclonal antibody, HBJ127 (IgG), which recognizes human gp125 antigen, specifically bound to gp125-positive target cancer cell lines, KU-1, T24, MKN-7, SKBr-3 and LS174T. Flow cytometric analysis using IL encapsulating carboxyfluorescein (CF) revealed that efficiencies of endocytosis varied among different cancer cells. The rate of IL internalization was in the order KU-1 > T24 > MKN-7 > SKBr-3 > LS174T. In 1 h incubation at 37 degrees C, all the four cell lines other than LS174T internalized about 60% of IL which were bound on their cell surfaces. KU-1, T24 and MKN-7, but not SKBr-3, significantly processed IL in endosome or lysosome. On the contrary, 80% of CIL bound to LS174T remained on the cell surface even after 2 h incubation. Furthermore, we evaluated the cytotoxic activities of CIL against the same panels of cancer cells. CIL inhibited the growth of all cancer cells tested in antibody-dependent manner, but, contrary to our expectation, KU-1 and T24 cells, which showed significant endocytosis activity, required a 7-14-fold higher amount of ADM binding than LS174T cells with low endocytosis activity for 50% cell growth inhibition. The difference of sensitivity to free ADM was only within 2.3-fold among those cancer cells. These results showing that liposomal ADM endocytosed is less effective than that remaining on the cell surface suggest that endocytosis is not necessarily required for cytotoxicity of CIL.

Epitope mapping of bovine serum albumin using monoclonal antibodies coupled with a photoreactive crosslinker

Antigenic determinants (epitopes) on bovine serum albumin (BSA) to anti-BSA monoclonal antibodies (mAbs) were assessed by means of photoaffinity labeling. Anti-BSA mAbs, AB3 and AB6, were modified with an 125I-labeled photoreactive crosslinker, sulfosuccinimidyl 2-(p-azidosalicylamido)ethyl-1,3'-dithiopropionate (SASD) and then bound with BSA. The complex yielded was irradiated with UV light to facilitate covalent binding of the modified mAb with BSA. Reduction of the product with 2-mercaptoethanol revealed that radioactivity of 125I-SASD was specifically introduced into BSA, probably near the mAb combining site(s). The radiolabeled or native BSA was digested with V8 protease and the peptides produced were assessed for their amino acid sequence, the radiolabeled amino acids contained, and their reactivity to mAb. The results indicated that AB3 mAb recognized an epitope in the region of Ala-537 to Asp-554 on a linear part of the BSA molecule, whereas AB6 mAb probably recognized an epitope of the assembled form present in a peptide of Asp-299 to Glu-338.

Alterations of specific and nonspecific binding of monoclonal antibody by introduction of acidic and hydrophobic groups

AB-6 monoclonal antibody (mAb) against bovine serum albumin (BSA) was coupled with beta-alanine or n-propylamine using a heterobifunctional cross-linking reagent, N-(epsilon-maleimidocaproyloxy)succinimide (EMCS) and a linker, poly-L-cysteine to introduce acidic or hydrophobic groups into the mAb. The mAb molecules coupled with beta-alanine at lower than 1:16 molar ratios and those coupled with n-propylamine at 1:14 retained the original reactivity to BSA but modification with higher amounts of beta-alanine or n-propylamine decreased the reactivity. In contrast, nonspecific bindings of AB-6 mAb to a plastic culture plate and tumor (MDA-MB-453) cells were decreased by modification with beta-alanine and increased by n-propylamine. These results suggested that introduction of acidic groups, and hydrophobic groups to antibody leads to fluctuations in the non-specific binding of antibody.

Binding of serum albumin on tumor cells and characterization of the albumin binding protein

The binding of bovine (BSA) and human serum albumin (HSA) to the surface of human and mouse tumor cells in vitro was examined by flow cytometry using monoclonal antibodies against these albumins. Both isologous and heterologous types of albumin bound firmly on several lines of human and mouse tumor cells. The cell-bound albumin was removable by protease (actinase) treatment or by culture in albumin-free medium for more than 2 days, but not by simple washing. The amount of albumin capable of binding to the tumor cell surface differed among the 9 tumor cell lines tested. As determined with radioiodinated BSA, about 2.6 x 10(6) BSA molecules/cell could bind to MDA-MB-453 human mammary cancer cells, which exhibit high binding capacity as to BSA. A unique peptide having a molecular weight of 18 kDa was detected on gel electrophoresis in extracts of tumor cells or normal aortic endothelial cells which had been treated with radioiodinated, photocross-linker-labeled BSA or HSA, followed by UV-irradiation. This peptide was also immuno-precipitated with an anti-BSA or anti-HSA monoclonal antibody. With both methods, the yield of the peptide was decreased by previous addition of an excess amount of unlabeled BSA or HSA. These findings indicated that the 18-kDa peptide expressed on both normal aortic endothelial cells and tumor cells is a principal serum albumin-binding protein, and that this protein binds both BSA and HSA.

Pre-Kupffer like CD4/CD8 double positive mononuclear cells present in rat liver

Nonparenchymal cells isolated from Fischer rat liver were separated into subpopulations by passage through a nylon wool column and/or culturing in a plastic plate. Besides typical Kupffer cells, we detected a unique population of cells (called PKu cells) which were plastic adherent but did not spread on a short term culture, were nonadherent on nylon wool, and were nonphagocytic, as opposed to Kupffer cells. Both Kupffer cells and PKu cells expressed CD4 (recognized with W3/25 mAb), CD8 (OX-8), a NK cell antigen (3.2.3), and a monocyte antigen (OX-41), as assessed by flow cytofluorometry. However, the proportion of cells bearing high densities of CD8 and 3.2.3 antigens was much larger for PKu cells than for Kupffer cells. Reverse transcriptase-PCR analysis of CD8 mRNA revealed that PKu cells expressed the CD8 alpha chain but not the beta chain. When PKu cells were treated with phorbol 12-myristate 13-acetate (PMA), they exhibited spreading and phagocytic activities, and showed a similar morphology to Kupffer cells in the spread form. Moreover, PMA treatment decreased the high density of CD8 antigen on PKu cells. These findings indicated that PKu cells present in normal rat liver are precursors of Kupffer cells.

Derivation and application of monoclonal antibodies recognizing several epitopes on bovine serum albumin

Three (AB-3, AB-4 and AB-6) monoclonal antibodies (mAb) to bovine serum albumin (BSA) were derived and characterized for their physicochemical and immunological properties. AB-3 recognized an epitope distinct from epitopes recognized by AB-4 and AB-6 as determined by binding inhibition assay. AB-4 and AB-6 mAbs recognized similar but not identical epitopes on BSA. Based on the antigenic specificity, we applied these mAbs to quantitative analysis of BSA in medium and to depletion of BSA from culture medium containing fetal calf serum (FCS). For quantitative analysis, we employed a sandwich enzyme-linked immunosorbent assay (ELISA) using biotinylated AB-3, solid-phase of AB-6 and an avidin-biotin-peroxidase complex system. This assay was highly sensitive and quantitative in the range of BSA concentration at 10 to 1,500 ng/ml. To deplete BSA from medium, we prepared affinity-gel coupled to AB-6. Repeated treatment of FCS-containing medium with the affinity-gel efficiently depleted BSA from the medium. The depletion capacity was 0.74 to 1.0 moles of BSA/mole of coupled mAb.

Expression of Thy-1 on rat T cells and its relevance as a maturation marker of T cells in rats

Expression of Thy-1 and CD3 antigens on thymocytes and the nylon wool-non-adherent (nylon-nonad) fractions of peripheral lymphocytes in F344 rats was studied by flow cytometry using anti-Thy-1 and anti-CD3 antibodies. In terms of the expression and density of Thy-1 and CD3, the thymus and peripheral lymphoid tissues in rats contained different populations. Nearly all thymocytes showed a high density of Thy-1 (Thy-1hi); a small population with a low density of Thy-1 (Thy-1lo) was found in CD3 bright-positive (CD3hi) thymocytes. Three-color analysis with CD4, CD8 and Thy-1 revealed Thy-1lo thymocytes to have mainly CD4 or CD8; Thy-1hi thymocytes also contained CD4 or CD8 single-positive (SP) cells as a minor population. Thus, SP thymocytes bearing CD3 were divided into two populations by evaluation of the density of Thy-1. Of peripheral CD3+ T cells, 15% showed a low density of Thy-1+ and the others were Thy-1-. Both T cells responded to anti-CD3 monoclonal antibody (mAb). However, no Thy-1hi T cells were found in peripheral lymphoid tissues. These results suggested that SP thymocytes in rats develop with the reduction of Thy-1, but not with its loss, and are newly supplied to peripheral lymphoid tissues as the phenotype, Thy-1lo, and are altered to Thy-1- T cells. Analysis of each cell size and disappearance of peripheral Thy-1lo T cells with age supported the above conclusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficient immunostaining of tissue sections with chemically modified monoclonal antibody

Monoclonal antibodies (mAbs) were modified with a photo-cross linker, sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1,3'-dithiopropionate (SAND), and their efficacy in immunohistochemical staining of tissue sections was examined comparatively with that of unmodified mAbs. mAbs used were HBJ127 and SV2-61 gamma which recognized a proliferation-associated human gp125 cell surface antigen and a human c-erbB-2 protooncogene product, respectively. Both mAbs could stain relevant cancer tissue in frozen sections but not that in paraffin sections. Whereas SAND-modified mAbs intensely stained the cancer tissue in paraffin sections too, and the UV irradiation to SAND-modified mAb-treated tissue sections further increased the intensity of the staining. Scatchard plot analysis using 125I-labeled mAbs indicated that the augmentation of staining capacity by the SAND modification is due to the increase of the mAb amount capable of binding to the antigen.

Characterization of the T cells in aged rat bone marrow

In this study, we determined the characteristics of CD3-positive (CD3+) T cells existing in rat bone marrow (BM). In contrast to splenic T cells, BM CD3+ T cells are composed of a higher proportion of CD8+ T cells, and the number of both cell types increased with age. Such CD3+ T cells in aged rats showed a similar usage of TCR V beta as splenic T cells, suggesting that BM CD3+ T cells are thymus-dependent and composed of an ordinary population in view of the expression of the TCR beta-chain. Purified T cells obtained from aged rat BM showed a markedly proliferative response by stimulation with immobilized anti-CD3 mAb, as did splenic T cells. However, the addition of BM non-T cells completely inhibited the response of both BM and splenic T cells in vitro. These results suggest that T cells in rat BM are negatively regulated by BM non-T cells in their response to the TCR-mediated signal not to disrupt the microenvironment of the BM.

Specific targeting of in vitro-activated human antitumour effector cells using anti-CD3 x anti-c-erbB-2 bispecific antibody

Bispecific antibody (BSAb) consisting of anti-CD3 plus anti-c-erbB-2 Fab fragments for the application to adoptive tumour immunotherapy was prepared. This bifunctional hetero-F(ab')2 antibody reacted with both human CD3+ T cells and c-erbB-2 positive human tumour cells. Human CD8+ T cells activated with immobilized anti-CD3 plus interleukin 2 showed marginal cytotoxicity against tumour cells. However, addition of the prepared BSAb into the culture resulted in a marked augmentation of the cytotoxicity by the activated CD8+ T cells in a dose-dependent manner. The enhanced cytotoxicity of CD8+ T cells in the presence of BSAb was specific for c-erbB-2 positive tumour cells. Moreover, it was demonstrated that anti-CD3 x anti-c-erbB-2 BSAb was also effective for the specific targeting of various kinds of in vitro-activated antitumour effector cells such as lymphokine-activated killer cells, CD4+ helper/killer cells, gamma delta T cells and activated tumour-infiltrating CD8+ T cells. These results indicated that BSAb consisted of anti-CD3 and anti-c-erbB-2 will become a useful tool for the adoptive tumour immunotherapy of human cancer expressing c-erbB-2 oncogene products.

Enhanced binding to antigen of monoclonal antibodies modified with a crosslinker

Modification of monoclonal antibodies (mAbs) with a photo-crosslinker, sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1, 3'-dithiopropionate (SAND), enhanced their antigen binding activity. By SAND modification, SV2-61 gamma mAb against human c-erbB-2 protooncogene product could immunoprecipitate approximately an 8-fold greater amount of antigen, and AB-3 mAb against bovine serum albumin (BSA) bound to BSA more efficiently than unmodified mAb as determined by an enzyme-linked immunosorbent assay. Relative binding affinity of SAND-modified AB-3 was about 4-fold of unmodified AB-3. Augmented binding of mAbs was observed with or without photosensitization.

Intracellular localization of UDP-glucuronosyltransferase expressed from the transfected cDNA in cultured cells

Liver UDP-glucuronosyltransferase (UDPGT) is localized in the endoplasmic reticulum (ER), with its catalytic domain exposed to the lumenal side of the membrane structure. The proteins expressed from the transfected UDPGT cDNA in cultured cells were found to be localized in the ER membrane. Its enzyme activity was in a latent state and was fully expressed in an in vitro assay system when the membrane integrity was disrupted by a detergent, Triton X-100, suggesting that the orientation of the expressed enzyme in the membrane was the same as that of the liver enzyme. To investigate how the expressed UDPGT was retained in the ER, we constructed chimeric plasmids of cDNAs of UDPGT and ErbB2 which is a receptor protein localized in the cell membranes. Analysis of chimeric proteins expressed in the stable transformants of the cultured cells transfected with these plasmids to reveal that the cytoplasmic tail of UDPGT is responsible for the ER retention of the expressed proteins. Deletion and mutation analysis in the cytoplasmic tail of the enzyme demonstrated that the two lysine residues positioned at 3 and 5 from the C-terminus of the molecule are important for conferring the ER residency. Furthermore, the distance of the ER retention signal composed of the two lysine residues from the transmembrane domain may be influential for the efficiency of the ER retention activity.

An enzyme immunoassay for cell proliferation using monoclonal antibodies directed against a cell proliferation-associated antigen

An enzyme immunoassay (EIA) for assessment of cell activation and proliferation was developed by the use of monoclonal antibodies (MoAb) directed against a ubiquitous growth-associated antigen, gp125. Test cells distributed in a microtest plate were labeled with anti-rat gp125 MoAb, B3, for rat cells or anti-human gp125 MoAb, HBJ127, for human cells and subsequently with rabbit anti-mouse immunoglobulins. The cell-bound antibody was assessed by a colorimetric enzyme assay using horse-radish peroxidase-modified protein A and 2,2'-azinobis(3-ethylbenzthiazoline sulfonic acid). To terminate the reaction and to make the reaction mixture transparent, sodium dodecyl sulfate (SDS) was added to the mixture. The intensity of the developed color was measured by use of a multiwell scanning spectrometer. The titration curves obtained by the EIA for cells were practically similar to those obtained by the conventional 3H-thymidine (Tdr) uptake method, and the appropriate cell number to be used for the assay was indicated to be 3 to 50 x 10(3) cells per well. This method was applicable not only for quantitation of cell number of growing cells but also for measuring mitogenic responses of lymphocytes as revealed by the data obtained from Con A stimulation of lymphocytes. These results indicate that this new EIA method using anti-gp125 antibodies is useful for quantitative assays of cell growth and cell activation in the research fields of oncology and immunology.

Assay of cell surface-bound immunoliposomes using monoclonal antibody reactive with a cross-linking reagent

A monoclonal antibody (mAb) reactive with a crosslinking reagent, N-(m-maleimidobenzoyl)dipalmitoylphosphatidylethanolamine (mMBPE), in liposomes was produced from a hybridoma clone established by a fusion between P3X63Ag8.653 mouse myeloma cells and spleen cells from a BALB/c mouse hyperimmunized with the antibody-coated liposomes containing mMBPE. Using this mAb (termed AL-6), the quantity of immunoliposomes bound on target tumor cells was assessed by flow cytofluorometry. The results obtained using fluorescein isothiocyanate-coupled AL-6 allowed the enumeration not only of the immunoliposomes bound on all tumor cells but also those on individual target tumor cells. The relevance of this assay method was confirmed by a comparison with another assay method of cell-bound liposomes using immunoliposomes containing carboxyfluorescein in the vesicles.

HumanC-ERBB-2 proto-oncogene product as a target for bispecific-antibody-directed adoptive tumor immunotherapy

To develop an efficient strategy for the targeting of anti-tumor effector cells, we prepared bispecific antibody (BsAb) containing anti-CD3 and an anti-c-erbB-2 proto-oncogene product. The prepared BsAb specifically reacts with both c-erbB-2-positive tumor cells and CD3+ CTL. Human CD4+ helper/killer T cells, induced from peripheral-blood mononuclear cells by activation with immobilized anti-CD3 monoclonal antibody (MAb) plus IL-2, showed no significant cytotoxicity against tumor cells. However, treatment of human CD4+ helper/killer cells with the BsAb caused the induction of specific cytotoxicity against c-erbB-2-positive tumor cells. CD4+ helper/killer cells also produced significant amounts of IL-2 during co-culture with c-erbB-2-positive tumor cells in the presence of the BsAb. Moreover, by combination with the BsAb, CD4+ helper/killer cells showed a strong in vivo anti-tumor effect against c-erbB-2 transfectant or human colon-cancer cells implanted in nude mice. Our results strongly suggest that the c-erbB-2 proto-oncogene product on human tumor cells may be a good target for BsAb-directed adoptive tumor immunotherapy.

Release of esterase from murine lymphokine-activated killer cells in antibody-dependent cellular cytotoxic reaction

Release of granule enzyme(s) (BLT esterase) in the antibody dependent lymphokine-activated killer (LAK) cell-mediated cytotoxic reaction (LAK ADCC) was studied using LAK cells induced from murine splenocytes and thymocytes, various human tumor cells and relevant monoclonal antibodies (mAbs) to the tumor cells. BLT esterase was not significantly released from LAK cells in direct LAK cell-mediated cytotoxic reactions (LAK CMC). However, cultures of LAK cells and IgG-coated target tumor cells resulted in release of the enzyme concomitantly with target cell lysis, although esterase release proceeded faster than target cell lysis. Anti-LFA-1 mAb showed an inhibitory effect on LAK CMC but not on either LAK ADCC or BLT esterase release in the ADCC. These results indicate that exocytosis of granule enzyme from LAK cells is triggered by stimulation of Fc receptor on LAK cells and that LAK CMC and LAK ADCC differ in their lytic mechanism in terms of the release of BLT esterase.

Immunohistochemical analysis of c-erbB-2 oncogene product and epidermal growth factor receptor expression in human urinary bladder carcinomas

Expression of the product of the c-erbB-2 gene, a proto-oncogene related to, but distinct from c-erbB-1 encoding the epidermal growth factor receptor (EGF-R), was investigated in human urinary bladder carcinomas. In addition, levels of EGF-R and transferrin receptor were also analyzed using an immunohistochemical approach, and the results compared with histological pattern and grading, and tumor staging. Increased expression of c-erb B-2 product was found in 32% of cases (7/22), a positive reaction being observed in 60% of transitional cell carcinoma (TCC) Grade 3 lesions (3/5), 20% of Grade 2 TCCs (2/10) and 100% of adenocarcinomas (AC) (2/2), but in none of the cases of squamous cell carcinoma (SCC). Although no statistical correlation with staging was evident, TCCs or SCCs of high grade and stage often showed EGF-R-positive staining, whereas other well differentiated lesions and normal bladder epithelium were generally negative. Most cases of urinary bladder carcinoma were positive for the transferrin receptor, which was not detected in normal bladder. The results thus suggested that a positive reaction for c-erbB-2 product is correlated with TCC histological grading or AC morphology. A high intensity of EGF-R staining in human bladder carcinomas may be associated with poor differentiation and invasion, whereas transferrin receptor expression might reflect tumor growth.

[Prostate specific monoclonal antibody gained by glycolipid immunization]

Extraction of glycolipid component from hypertrophic and cancerous prostatic tissue were performed using chloroform-methanol solution and isopropanol-hexan-solution. The extract was separated into the "upper phase" and "lower phase" by Folchs fractionation technic. Each fraction was conjugated with acid treated salmonella minesota and than it was injected subcutaneously, intra-peritoneally and finally intravenously to BALB/c mice. Spleen cells from immunized mice were fused with P3X63, and antibody APG1 was obtained. APG1 shows a preferential reactivity towards prostatic tissue by the immunohistochemical analysis. Furthermore, the immunohistochemical analysis using enzyme and acid treated tissue and TLC immunostaining indicate that this monoclonal antibody specifically recognizes the sialylglycochain expressed in the prostatic tissue.

Increase in colony stimulating factor (CSF) in serum and augmentation of CSF responsiveness of lymphoid mononuclear cells by acute Trypanosoma cruzi infection in mice

Acute infection of Trypanosoma (T.) cruzi to C3H/HeN mice caused the induction of a higher level of serum colony stimulating factor (CSF) activity to support the proliferation of mouse bone marrow cells. The CSF activity reached a maximum 2 days after the infection and declined thereafter. Spleen cells of the T. cruzi-infected mice showed higher levels of responsiveness to CSF in L929-conditioned medium, mouse recombinant GM-CSF and infected mouse sera as compared with normal mouse spleen cells. The induction of CSF-responding cells became plateau 4 days after the infection and it decreased thereafter. In concomitant with the production of CSF activity in the infected mouse sera, large granular cells bearing high intensity of Mac-2 antigen increased in the infected mouse spleen. These cells were nylon nonadherent and displayed inhibitory effect on T cell response to Con A. These findings indicate that T. cruzi infection induces augmentation of in vivo CSF production, leading to the abnormal proliferation of CSF-responding cells and that augmented production of, and responsiveness to, CSF might be one of important mechanisms responsible for the induction of immune abnormalities in T. cruzi-infected mice.

A microtestplate-immunofluorescence assay for anti-Trypanosoma cruzi antibodies

A new microassay method for the detection of anti-Trypanosoma (T.) antibodies was developed by using Terasaki's microtestplates, and T. cruzi or other parasites were immunofluorescently labeled with polyclonal or monoclonal anti-T. cruzi antibodies. The fluorescence intensity of immunofluorescently stained parasites was assessed by either visual observation or quantitative analysis using a microscopic spectrophotometer. Although the sensitivity of the microtestplate assay was nearly equal to that of the conventional glass slide assay or ELISA, this method is easier in the assay procedures and spares the amount of antibodies and the number of target parasites requisite to the assay.

Production and characterization of monoclonal antibodies against Trypanosoma cruzi-associated antigens

Nine monoclonal antibodies (mAb) recognizing characteristic antigens in Trypanosoma (T.) cruzi were obtained from hybridomas which had been established by a fusion between mouse myeloma cells and the spleen cells of a mouse immune to the epimastigote form of T. cruzi (Tulahuen strain). Antigen specificities of these mAb were assessed by an indirect immunofluorescence (IIF) method using T. cruzi in different life cycles (amastigote and trypomastigote) and other members of the Trypanosomatidae. The mAb were classified into 3 groups from their reaction patterns to different parasites: 1) The strain specific mAb that reacted only with T. cruzi Tulahuen epimastigote, 2) the species specific mAb that reacted with all T. cruzi strains but not with other species of parasites, and 3) the mAb that were cross-reactive with other species of Trypanosomatidae. Most mAb were specific to epimastigote form of T. cruzi, but some reacted weakly with trypomastigote and amastigote form of the parasites. Immunoblotting and glycolipid analyses of the membrane fraction of homogenized parasites using the mAb identified at least 3 distinct antigenic molecules; those of protein nature having Mr. 43,000 and 58,000 and Mr. 43,000 and 62,000 and molecule(s) of glycolipid nature.

Strain differences in susceptibility to 2-acetylaminofluorene and phenobarbital promotion of hepatocarcinogenesis: immunohistochemical analysis of cytochrome P-450 isozyme induction by 2-acetylaminofluorene and phenobarbital

Strain differences in the expression of cytochrome P-450 isoenzymes (P-450s) during enhancement of hepatocarcinogenesis by 2-acetylaminofluorene (2-AAF) and phenobarbital (PB) were investigated immunohistochemically using monoclonal antibodies against phenobarbital (PB) (APF3) or 3-methylcholanthrene (3-MC) (APH8) inducible P-450s. LEW, SD, WBN, F344, SHR, NAR, Wistar and ODS rats were studied, the first five strains proving to be less susceptible to 2-AAF induction of APH8 while responding strongly to the promoting influence of this chemical, as reported previously. The other three strains, NAR, Wistar and ODS, demonstrated greater inducibility, this correlating with an observed resistance to promotion by 2-AAF. PB administration was not associated with any strain difference in APF3 cytochrome P-450 inducibility except in the ODS rat, in which its effects were minimal. The results provide direct evidence that differential expression of cytochrome P-450 species plays a major role in determining responsiveness to hepatocarcinogenesis-promoting agents such as 2-AAF.