Biomedical subjects

A Gorter

Publications and source records attributed to A Gorter.

At least 19 recordsLinked to original sources

PubMed2006

The absence of CCL2 expression in cervical carcinoma is associated with increased survival and loss of heterozygosity at 17q11.2.

To determine whether CCL2 mRNA expression is beneficial or detrimental for cervical cancer patients, the association between the expression of this molecule by cervical tumour cells, the number of tumour-associated macrophages, and clinicopathological parameters such as recurrence, relapse-free survival, and overall patient survival was investigated. In cervical cancer samples from 93 untreated cervical cancer patients, the CCL2 mRNA expression level was quantified using RNA in situ hybridization and verified using real-time quantitative RT-PCR. The number of tumour-associated macrophages was determined using immunohistochemistry. Furthermore, the study investigated whether lack of CCL2 expression was due to genetic alterations near the 17q11.2 (CCL2 genomic) region. CCL2 mRNA expression by cervical tumour cells was associated with the number of tumour-associated macrophages (p < 0.001). Lack of CCL2 mRNA expression (15 samples; 16%) was associated with increased cumulative relapse-free survival (log rank test, p = 0.030), increased cumulative overall survival (log rank test, p = 0.024), less post-operative surgery, reduced local and distant recurrence, reduced vascular invasion, and smaller tumour size (<40 mm). The absence of CCL2 mRNA expression corresponded with loss of heterozygosity (LOH) at 17q11.2 in five of six samples. The increased cumulative relapse-free survival and cumulative overall survival of cervical cancer patients lacking tumour cell-associated CCL2 mRNA suggest that the tumour-associated macrophages support tumour progression, presumably by promoting angiogenesis and production of growth factors.

Biomarkers, Tumor↗

PubMed2004

CD55 expression patterns on intestinal neuronal tissue are divergent from the brain.

BACKGROUND: and objectives: In this study, we investigated how enteric plexuses protect themselves from complement mediated attack. For this purpose, the expression patterns of membrane bound complement regulatory proteins (mCRP) and their association with C3 deposition was determined. In addition, mCRP expression patterns of enteric plexuses were compared with those in the central nervous system (CNS). METHODS: Immunohistochemical stainings were performed to discriminate neuronal cells from glial cells and to detect the presence of CD46, CD55, CD59, and C3d. RNA in situ hybridisation (RISH) was used to determine the cell types that produce CD55 mRNA. RESULTS: Enteric plexuses minimally expressed CD46 whereas CD55 and CD59 were highly expressed. CD55 expression was also observed in a ring around Auerbach's plexuses which was not observed for CD46 and CD59. C3d was deposited around the plexuses but plexus cells themselves did not stain for C3d. In contrast with CNS neurones, enteric neurones were shown to express CD55 whereas enteric glial cells did not. This was confirmed with CD55 RISH. Phospholipase C mediated cleavage of CD55 demonstrated that CD55 was most likely attached to elastic fibres surrounding the plexus. Attached CD55 might protect CD55 negative glial cells from complement mediated injury during inflammatory reactions. CD55 on elastic fibres surrounding the plexuses most likely originated from enteric neuronal cells. CONCLUSION: In contrast with the CNS, enteric neurones express CD55 and enteric glial cells lack CD55 expression. CD55, produced by neuronal cells, attached to elastic fibres surrounding the plexuses is proposed to protect the CD55 negative glial cells within plexuses.

Brain↗

PubMed2003

Membrane-bound complement regulatory proteins inhibit complement activation by an immunotherapeutic mAb in a syngeneic rat colorectal cancer model.

MAb-mediated immunotherapy offers a potential tool for destroying metastasizing colorectal tumor cells. Promising results have been obtained by using xenograft models. However, overexpression of membrane-bound complement regulatory proteins (mCRP) impedes complement-mediated destruction of tumor cells in vitro. mCRP operate in a species selective manner. Therefore a syngeneic animal model is needed to investigate the contribution of mCRP in mAb-mediated immunotherapy. Here we present a syngeneic rat colorectal carcinoma model, which fulfills the conditions necessary to investigate the effect of mCRP expression on mAb-mediated immunotherapy of metastases of solid tumors.CC531 rat colorectal cancer cells were injected subcapsularly into the liver of syngeneic WAG/Rij rats. Four mAb (MG1(IgG2a), MG2(IgG2a), MG3(IgG3) and MG4(2a)(IgG2a)) directed against CC531 cells, were tested for their complement activating abilities in vitro and tumor homing capacities in vivo. Only MG4(2a) was found to activate complement in vitro and home to the tumor cells in vivo. This mAb induced C3-deposition and C-mediated lysis of CC531 cells in vitro when the effects of the C-inhibitors Crry/p65 and CD59 were neutralized. This implies an important role for these mCRP in restricting the effector functions of tumor-associated mAb on these cells. Although C activation could be induced by MG4(2a) in situ on tumor tissue sections, no deposition of C3 could be found on the tumor cells positive for MG4(2a) in vivo. This suggests that complement activation in vivo was inhibited by mCRP. The results indicate the suitability of this syngeneic animal model for studying the effects of mAb immunotherapy. However, the effect of mCRP on tumor cells need to be overcome, e.g. by the use of mAb against tumor antigens and mCRP.

Animals↗

PubMed2003

Cytokines affect resistance of human renal tumour cells to complement-mediated injury.

Overexpression of membrane-bound complement regulatory proteins (mCRPs) on tumour cells may hamper the effect of immunotherapy with complement-activating monoclonal antibody (MoAb). Therefore, it is important to investigate whether cytokines can downregulate the expression of mCRP on tumour cells. In this study, the effect of 10 cytokines on the expression of the mCRP CD46, CD55 and CD59 and the renal tumour-associated antigen G250/MN/CAIX on four human renal tumour cell lines and proximal tubular epithelial cells was determined by flow cytometry. In addition, it was measured whether changes in the expression of the classical pathway regulatory proteins CD55 and CD59 had an effect on C3 deposition and lysis. Interleukin-1beta (IL-1beta) consistently downregulated the expression of CD46 and CD59; IL-4 consistently downregulated the expression of CD46 and transforming growth factor-beta1, consistently downregulated the expression of both CD46 and CD55. However, treatment with IL-1beta and IL-4 also decreased the expression of G250/MN/CAIX. Changes in the expression of CD55 and CD59 were associated with changes in the amount of C3 deposited and the extent of complement-mediated lysis, respectively. This suggests that clinical immunotherapy, consisting of treatment with cytokines and MoAb, may induce either up- or downregulation of CD55 or CD59 and thus affect the effectiveness of immunotherapy with MoAb.

Antibodies, Monoclonal↗

PubMed2001

Blockade of the granzyme B/perforin pathway through overexpression of the serine protease inhibitor PI-9/SPI-6 constitutes a mechanism for immune escape by tumors.

The concept for cellular immunotherapy of solid tumors relies heavily on the capacity of class I MHC-restricted cytotoxic T lymphocytes (CTLs) to eliminate tumor cells. However, tumors often have managed to escape from the cytolytic machinery of these effector cells. Therefore, it is very important to chart the mechanisms through which this escape can occur. Target-cell killing by CTLs involves the induction of apoptosis by two major mechanisms: through death receptors and the perforin/granzyme B (GrB) pathway. Whereas tumors previously were shown to exhibit mechanisms for blocking the death receptor pathway, we now demonstrate that they also can resist CTL-mediated killing through interference with the perforin/GrB pathway. This escape mechanism involves expression of the serine protease inhibitor PI-9/SPI-6, which inactivates the apoptotic effector molecule GrB. Expression of PI-9 was observed in a variety of human and murine tumors. Moreover, we show that, indeed, expression results in the resistance of tumor cells to CTL-mediated killing both in vitro and in vivo. Our data reveal that PI-9/SPI-6 is an important parameter determining the success of T cell-based immunotherapeutic modalities against cancer.

Animals↗

PubMed2001

Cytokine profile of cervical cancer cells.

OBJECTIVE: In patients with cervical carcinoma, the presence of cytokines produced by T(H)2 cells, and the presence of an eosinophilic inflammatory infiltrate, has been associated with a less effective immune response and tumor progression. In the present study, we have investigated the cytokine profile of cervical carcinoma cells. In addition, we have measured whether differences in cytokine profiles between normal and malignant cervical epithelial cells are present. METHODS: For this purpose we have determined the mRNA expression patterns of 20 relevant cytokines by RT-PCR and Southern blotting in 3 normal primary cervical epithelial cell cultures (NPE) and 10 cervical cancer cell lines (CCCL). RESULTS: TGF-beta(1), IL-4, IL-12p35, and IL-15 were produced by all CCCL and NPE. TNF-alpha, IL-10, IL-5, and RANTES were present in most NPE, but not in any of the CCCL. MCP-1 was expressed in all CCCL but in only one NPE. The presence of the anti-inflammatory cytokine TGF-beta(1) in cervical carcinomas was confirmed by RNA in situ hybridization on tissue sections of carcinomas from which the CCCL originated. CONCLUSIONS: Our results suggest that cervical carcinoma cells produce immunomodulatory cytokines and that cytokine expression patterns change after malignant transformation. The implications of locally produced cytokines by cervical cancer cells are further discussed.

Blotting, Southern↗

PubMed2001

Pharmacokinetics of differently designed immunoliposome formulations in rats with or without hepatic colon cancer metastases.

PURPOSE: Compare pharmacokinetics of tumor-directed immunoliposomes in healthy and tumor-bearing rats (hepatic colon cancer metastases). METHODS: A tumor cell-specific monoclonal antibody was attached to polyethyleneglycol-stabilized liposomes, either in a random orientation via a lipid anchor (MPB-PEG-liposomes) or uniformly oriented at the distal end of the PEG chains (Hz-PEG-liposomes). Pharmacokinetics and tissue distribution were determined using [3H]cholesteryloleylether or bilayer-anchored 5-fluoro[3H]deoxyuridine-dipalmitate ([3H]FUdR-dP) as a marker. RESULTS: In healthy animals clearance of PEG-(immuno)liposomes was almost log-linear and only slightly affected by antibody attachment; in tumor-bearing animals all liposomes displayed biphasic clearance. In normal and tumor animals blood elimination increased with increasing antibody density; particularly for the Hz-PEG-liposomes, and was accompanied by increased hepatic uptake, probably due to increased numbers of macrophages induced by tumor growth. The presence of antibodies on the liposomes enhanced tumor accumulation: uptake per gram tumor tissue (2-4% of dose) was similar to that of liver. Remarkably, this applied to tumor-specific and irrelevant antibody. Increased immunoliposome uptake by trypsin-treated Kupffer cells implicated involvement of high-affinity Fc-receptors on activated macrophages. CONCLUSIONS: Tumor growth and immunoliposome characteristics (antibody density and orientation) determine immunoliposome pharmacokinetics. Although with a long-circulating immunoliposome formulation, efficiently retaining the prodrug FUdR-dP, we achieved enhanced uptake by hepatic metastases, this was probably not mediated by specific interaction with the tumor cells, but rather by tumor-associated macrophages.

Animals↗

PubMed2001

Role of NK cells in adoptive immunotherapy of metastatic colorectal cancer in a syngeneic rat model.

This article reviews our immunotherapy research with natural killer (NK) cells in a syngeneic rat colorectal cancer liver and lung metastasis model. Using adoptive transfer of interleukin (IL)-2-activated NK cells, NK cells were shown to selectively infiltrate the tumors. More NK cells were found in tumors when the NK cells were directly injected into tumor-draining blood vessels than when the cells were injected in systemic blood vessels. Under optimal conditions, a limited, though significant, effect of adoptively transferred NK cells on tumor growth was shown. We observed that both endogenous and adoptively transferred NK cells were predominantly present in the stroma surrounding the tumor cell nodules. It is possible that they did not penetrate the nodules containing the tumor cells because of the presence of a basal membrane-like structure around these nodules. Adoptively transferred NK cells may initiate elimination of tumor cells by activating other effector cells, whereas some may eliminate tumor cells by direct cell-cell contact. A diverse array of molecules was shown to be involved in this process. CD45 on NK cells was found to be important in initiating the lysis-inhibitory signal upon binding of 'self' major histocompatibility complex (MHC) class I on potential target cells. Our results indicate that NK-cell cancer therapy is still promising and needs improvement.

Animals↗

PubMed2000

A possible role of CD46 for the protection in vivo of human renal tumor cells from complement-mediated damage.

It is still unclear which membrane-bound regulatory proteins (mCRP) are important in vivo to protect tumor cells from complement-mediated damage. To address this question, the expression levels of CD46, CD55, and CD59 were measured semi-quantitatively in situ on renal cell carcinomas and compared with the expression level and cellular distribution of these mCRP in proximal tubuli within each patient (n = 31). It was also determined whether the expression of mCRP on tumor cells is associated with deposition of C3d and C5b-9. CD46 expression was decreased on tumor cells; in contrast, CD55 was expressed on tumor cells (12 out of 31 samples), while it was not detected on proximal tubular epithelial cells (PTEC). Also, expression of CD59 on tumor cells was increased as compared with its expression on PTEC. Furthermore, the localization on the cell surface of mCRP as observed on PTEC was altered on tumor cells. Because expression of mCRP may limit a complement-mediated anti-tumor response, we determined whether complement deposition was associated with the expression level of CD46, CD55, and CD59. The presence of C3d on tumor cells was associated with a low expression level of CD46 (p < 0.02). The expression level of CD46 was also associated with a low tumor stage (p < 0.04). The results suggest that in vivo CD46 plays a role in the protection of human renal tumor cells from complement-mediated injury.

Antigens, CD↗

PubMed2000

Uptake of long-circulating immunoliposomes, directed against colon adenocarcinoma cells, by liver metastases of colon cancer.

Radiolabeled ([3H]cholesteryloleyl ether) immunoliposomes directed against rat colon adenocarcinoma CC531 cells were prepared by random coupling of a tumor cell-specific antibody, CC52, via a thio ether bond. In vitro binding experiments demonstrated a saturable and specific interaction of CC52-immunoliposomes, which could be inhibited by free non-coupled CC52 but not by irrelevant antibodies. The in vivo targeting potential of CC52-immunoliposomes, which were pegylated to achieve prolonged circulation times, was tested in an established rat liver CC531 metastasis model. Twenty-four hours after injection of the liposomes, 25% of the CC52-immunoliposomes were still present in the blood, which was comparable with the control liposomes (either with or without antibody). Liposomes were mainly taken up from the blood by the liver and the spleen, although hepatic uptake of the immunoliposomes was higher and splenic uptake was lower as compared to liposomes without antibody. Within the metastatic tumor nodules in the liver, uptake of both the CC52-immunoliposomes and non-specific immunoliposomes was significantly higher than that of control liposomes without antibody. Visualization of fluorescently or gold labeled CC52-immunoliposomes revealed that, although targeting to liver metastases was achieved, the immunoliposomes were mostly not associated with tumor cells but rather localized in tumor associated cells, probably macrophages.

Adenocarcinoma↗

PubMed1999

Selective transfer of a lipophilic prodrug of 5-fluorodeoxyuridine from immunoliposomes to colon cancer cells.

A monoclonal antibody against the rat colon carcinoma CC531 was covalently coupled to liposomes containing a dipalmitoylated derivative of the anticancer drug FUdR as a prodrug in their bilayers. We investigated the in vitro interaction of these liposomes with CC531 target cells and the mechanism by which they deliver the active drug FUdR intracellularly to the cells by monitoring the fate of the liposomal bilayer markers cholesterol-[(14)C]oleate and [(3)H]cholesteryloleylether as well as the (3)H-labeled prodrug and colloidal gold as an encapsulated liposome marker. After binding of the immunoliposomes to the cell surface, only limited amounts were internalized as demonstrated by a low level of hydrolysis of liposomal cholesterol ester and by morphological studies employing colloidal gold-labeled immunoliposomes. By contrast, already within 24 h immunoliposome-incorporated FUdR-dP was hydrolyzed virtually completely to the parent drug FUdR intracellularly. This process was inhibited by a variety of endocytosis inhibitors, indicating that the prodrug enters and is processed by the cells by a mechanism involving an endocytic process, resulting in intracellular FUdR concentrations up to 3000-fold higher than those in the medium. Immunoliposomes containing poly(ethyleneglycol) (PEG) chains on their surface, with the antibody coupled either directly to the bilayer or at the distal end of the PEG chains were able to deliver the prodrug into the tumor cells at the same rate as immunoliposomes without PEG. Based on these observations, we tentatively conclude that during the interaction of the immunoliposomes with the tumor cells the lipophilic prodrug FUdR-dP is selectively transferred to the cell surface and subsequently internalized by constitutive endocytic or pinocytic invaginations of the plasma membrane, thus ultimately delivering the prodrug to a lysosomal compartment where hydrolysis and release of parent drug takes place. This concept allows for an efficient delivery of a liposome-associated drug without the need for the liposome as such to be internalized by the cells.

Animals↗

PubMed1999

The regulatory role of CD45 on rat NK cells in target cell lysis.

To investigate the role of CD45 in rat NK cell function, we developed new mAbs directed against rat CD45. mAb ANK12 binds to a high molecular isoform of CD45 and mAb ANK74 binds to the common part on all known CD45 isoforms, as has been described for the anti-rat CD45 mAb OX1. The ability of these mAbs to affect NK cell-mediated lysis was tested using the Fc receptor-positive target cell line P815. mAb ANK12 was found to significantly enhance the lysis of P815, whereas ANK74 and the anti-CD45 mAb OX1 did not. In addition, cross-linking of the CD45 isoform by ANK12 induced tyrosine phosphorylation of specific proteins in NK cells. Subsequently, the involvement of CD45 in the negative signaling after "self" MHC class I recognition by rat NK cells was investigated. The anti-CD45 mAbs were found to affect NK cell-mediated lysis of syngeneic tumor cell lines, depending upon the expression level of MHC class I on target cells. mAbs ANK74 and OX1 only inhibited lysis of the syngeneic tumor cell lines that expressed low levels of MHC class I. Furthermore, both mAbs caused an inhibition of NK cell-mediated lysis of these tumor cell lines when MHC class I molecules on the tumor cell lines were masked by an Ab. These results suggest that CD45 regulates the inhibitory signal pathway after self MHC class I recognition, supposedly by dephosphorylation of proteins.

Animals↗

PubMed1999

Immune evasion of tumor cells using membrane-bound complement regulatory proteins.

Membrane-bound complement regulatory proteins (mCRPs) play an important role in the protection of cells from complement-mediated injury. It is now apparent that malignant tumor cells also express these proteins to escape complement attack. Here, Arko Gorter and Seppo Meri discuss the implications of complement resistance for the immunotherapeutic treatment of solid tumors with monoclonal antibodies.

Animals↗

PubMed1999

Antiproliferative effect of immunoliposomes containing 5-fluorodeoxyuridine-dipalmitate on colon cancer cells.

We have investigated the antiproliferative action towards CC531 colon adenocarcinoma cells of target cell-specific immunoliposomes containing the amphiphilic dipalmitoyl derivative of 5-fluorodeoxyuridine (FUdR-dP). FUdR-dP incorporated in immunoliposomes caused a 13-fold stronger inhibition of CC531 cell growth in vitro, during a 72-h treatment, than FUdR-dP in liposomes without antibody, demonstrating that the prodrug is efficiently hydrolysed to yield the active drug, FUdR, intracellularly. The intracellular release of active FUdR was confirmed by determining the fate of 3H-labelled immunoliposomal FUdR-dP. Treatments shorter than 72 h with FUdR-dP in immunoliposomes resulted in anti-tumour activities comparable to, or even higher than, that of free FUdR. The shorter treatments reflect more closely the in vivo situation and illustrate the potential advantage of the use of immunoliposomes over non-targeted liposomal FUdR-dP or free FUdR. Association of tumour cell-specific immunoliposomes with CC531 cells was up to tenfold higher than that of liposomes without antibody or with irrelevant IgG coupled, demonstrating a specific interaction between liposomes and target cells which causes an efficient intracellular delivery of the drug. Since biochemical evidence indicates a lack of internalization or degradation of the liposomes as such, we postulate that entry of the drug most likely involves the direct transfer of the prodrug from the immunoliposome to the cell membrane during its antigen-specific interaction with the cells, followed by hydrolysis of FUdR-dP leading to relatively high intracellular FUdR-levels. In conclusion, we describe a targeted liposomal formulation for the anticancer drug FUdR, which is able to deliver the active drug to colon carcinoma cells with high efficiency, without the need for the cells to internalize the liposomes as such.

Antibodies, Monoclonal↗

PubMed1998

A bispecific monoclonal antibody directed against both the membrane-bound complement regulator CD55 and the renal tumor-associated antigen G250 enhances C3 deposition and tumor cell lysis by complement.

Tumor cells may inhibit the induction of a complement-mediated inflammatory response through overexpression of membrane-bound regulators of complement activation. Therefore, it is of interest to determine the most efficient approach to block these membrane-bound complement regulators on tumor cells. In the present study, we first generated a bispecific mAb directed against both CD55, using the functional blocking mAb MBC1, and the highly expressed HLA class I molecule as a model for a tumor-associated Ag, using the mAb W6/32. Tumor cells opsonized with bispecific mAb W6/32*MBC1, then exposed to complement and subsequently stained for C3 deposition, were assessed by flow cytometric analysis. We found that opsonization with W6/32*MBC1 resulted in a 92% enhancement of C3 deposition on renal tumor cells as compared with opsonization with W6/32 alone and a 17% enhancement of the C3 deposition as compared with incubation with a mixture of both parental mAb. Based on these results, we developed a bispecific mAb recognizing both CD55 and the relatively low expressed renal tumor-associated Ag G250. Increasing concentrations of the bispecific mAb G250*MBC1 resulted in a 25 to 400% increase in C3 deposition on renal tumor cells as compared with C3 deposition in the presence of the parental mAb G250 alone. G250*MBC1 enhanced C3 deposition by 21% in comparison with a mixture of both parentals. Furthermore, opsonization of tumor cells with G250*MBC1 rendered these cells more sensitive to complement-mediated lysis. In conclusion, the bispecific mAb G250*MBC1 induces deposition of C3 and tumor cell lysis more efficiently than G250 alone.

Antibodies, Bispecific↗

PubMed1997

Characterization of three new membrane structures on rat NK cells which are involved in activation of the lytic machinery.

In this study, three membrane structures on rat NK cells which activate lysis of target cells were characterized. Furthermore, the role of adhesion molecules in this activation process, in particular the CD18-associated integrins, was investigated. Three rat NK-activation structures were identified which have not been previously described. These structures are apparently unique as they differed in molecular weight from known NK-activation structures. Cross-linking of these activation structures with specific mAbs and a Fc gamma R-positive tumor cell line (P815) resulted in enhanced killing of these target cells by NK cells. If the CD18-associated integrins were masked by the anti-CD18 mAb WT.3, the redirected killing of P815 was completely blocked. This indicates that the CD18-associated integrins play a crucial role in activation of NK cells. Furthermore, our results show that rat NK cells possess multiple activation structures.

Animals↗

PubMed1997

Lack of effect of different cytokines on expression of membrane-bound regulators of complement activity on human uveal melanoma cells.

Tumor cells are protected from antibody-dependent complement-mediated lysis by membrane-bound regulators of complement activation (m-RCA). m-RCA are expressed on uveal melanoma cells. We determined whether cytokine treatment affects expression of m-RCA on these cells in vitro. m-RCA expression on uveal melanoma cell lines was studied by flow cytometry, using monoclonal antibodies directed against CD46, CD55, and CD59. Cytokines studied were interferon-alpha (IFN-alpha), IFN-gamma, interleukin-1B (IL-1B), IL-12, and tumor necrosis factor-alpha (TNF-alpha). All three m-RCA were expressed on the uveal melanoma cell lines (CD59>>CD46>CD55), although in variable amounts. With a few exceptions, the cytokines had no effect on m-RCA expression. CD55 expression was not influenced by any of the cytokines. IFN-gamma downregulated expression of CD46 on one cell line (p < 0.01). TNF-alpha upregulated CD59 expression on two of the five cell lines (p < 0.012 and p < 0.001, respectively), which effect was dose dependent. IFN-alpha, IFN-gamma, IL1-beta, IL12, and TNF-alpha had limited effects on m-RCA expression on uveal melanoma cells in vitro.

Antineoplastic Agents↗

PubMed1996

Induction of microhematuria by an IgA isotype switch variant of a monoclonal anti-Thy-1.1 antibody in the rat.

IgA nephropathy (IgAN) is a chronic form of glomerulonephritis (GN) characterized by the deposition in the glomerular mesangium of mainly IgA. An experimental form of mesangial proliferative GN can be induced in rats by either polyclonal or monoclonal antibodies against Thy-1.1, a glycoprotein present on the surface of MC. The IgG-mediated renal inflammation is complement dependent and associated with influx of platelets and monocytes. In the present study we switched an IgG2a anti-Thy-1.1 (ER4G) producing hybridoma to an IgA anti-Thy-1.1 (ER4A) producing clone and analyzed the effects of IgA anti-Thy-1.1 in rats. FPLC analysis by gel filtration revealed that the IgA produced by the hybridoma cells was mainly dimeric and polymeric. Infusion of rats with purified ER4A (1 mg/kg) resulted in the deposition of IgA in a mesangial pattern in the glomeruli, similar to that found with ER4G. While administration of ER4G resulted in proteinuria, no significant urinary protein excretion was found in rats treated with ER4A. However, significant microhematuria was observed in rats receiving either ER4A or ER4G. Furthermore, the administration of ER4A was not accompanied by activation of complement, and no significant influx of monocytes or polymorphonuclear leukocytes was observed in contrast to the rats receiving ER4G. We conclude that microhematuria is selectively induced in Wistar rats by mouse IgA anti-Thy-1.1 without detectable complement-mediated injury to MC. These studies may be of importance in understanding the mechanisms leading to IgAN in patients.

Animals↗