Serum IL-6 levels are associated with significant coronary stenosis in cardiovascularly asymptomatic inner-city black adults in the US.

OBJECTIVES AND DESIGN: The objective of this study was to explore whether increased levels of inflammatory cytokines are associated with the risk of clinically silent coronary artery disease. SUBJECTS: Three-hundred-fifty-six black adults aged 25-54 residing in inner city of Baltimore, Maryland, United States were included in this study. METHODS: Sociodemographics were assessed as were lipid profiles, IL-6, tumor necrosis factor-alpha (TNF-alpha), soluble intercellular adhesion molecule-1 (sICAM-1), and high-sensitivity C-reactive protein (hs-CRP) levels. Computed tomography (CT) coronary angiography was performed. RESULTS: Coronary calcification was identified in 22.5 % participants and 14 % had significant (>or=50 %) coronary stenosis. Multiple logistic regression analyses suggested that IL-6 levels were independently associated with the presence of coronary calcification and significant coronary stenosis, while TNF-alpha, sICAM-1 and hs-CRP levels were not. CONCLUSIONS: This study underscores a critical role for IL-6 in atherosclerosis and suggests that IL-6 may be a marker for significant coronary stenosis in cardiovascularly asymptomatic individuals.

Coexpression of neuronal, glial, and major histocompatibility complex class II antigens on retinoblastoma cells.

This study identifies the presence of major histocompatibility complex class II antigens on retinoblastoma cells. In addition, the modulation of HLA-DR by interferon-gamma as well as the preferential expression of this major histocompatibility complex molecule over HLA-DQ is described. Double labeling experiments revealed that HLA-DR antigen is shared concomitantly with cells of glial and neuronal character. Investigations such as these underscore the possibility that expression of major histocompatibility complex class II antigens may function as immunological components in the host or play a role in the cellular differentiation of these tumor cells.

Detection of cytomegalovirus proteins by flow cytometry in the blood of patients undergoing hematopoietic stem cell transplantation.

Cytomegalovirus (CMV) infection and associated diseases continue to be a major complication encountered by patients undergoing high-dose chemoradiotherapy and hematopoietic stem cell transplantation (HSCT). A number of studies revealed that identification of CMV in the blood of HSCT patients was a predictor of future CMV disease. The purpose of this study was to determine if CMV proteins detected by flow cytometry could be a rapid and more quantitative way to monitor CMV infections and CMV antigenemia in HSCT patients. Preliminary studies showed that CMV immediate early (IE), early (E), and late (L) tegument proteins were specifically identified in CMV-infected cell lines and not in uninfected cells. We evaluated CMV antigen detection by flow cytometry in blood samples collected before and after transplantation in 56 serially collected blood samples from 17 HSCT patients and CMV protein expression was compared to CMV isolation. CMV IE and E proteins were not detected in any of the samples analyzed. However, CMV L protein detection by flow cytometry correlated with virus isolation in serially collected blood samples. Samples from 14 patients were evaluated by both techniques, at the same time intervals. There was a 100% correlation (8/8) between the lack of CMV antigen detection by flow cytometry and the failure to isolate infectious virus. Moreover, 5 of 6 patients who were positive for CMV L antigen by flow cytometry also were positive by virus isolation techniques. When flow cytometry and virus isolation did not detect CMV antigen on the same day, CMV positivity was first detected by flow cytometry. Then, 1-2 weeks later, positive virus isolation was documented. This study indicates that flow cytometric identification of CMV antigenemia correlates with isolation of CMV in HSCT patients and may be a predictive test for the rapid detection of CMV in the blood.

Interferon-gamma enhances the expression of retinal S-antigen, a specific neuronal cell marker.

Interferon-gamma (IFN-gamma) is a potent lymphokine which can modify a variety of cellular processes. One of the mechanisms involved in these processes is the ability of IFN-gamma to alter the regulation and expression of cellular proteins. Using analytical flow cytometry, we show that recombinant human IFN-gamma can enhance the expression of retinal S-antigen in retinoblastoma cells. This enhancement was selective since two other retinal cell proteins, interphotoreceptor binding protein (IRBP) and photo-6, were not affected by IFN-gamma treatment. Retinal S-antigen plays an important role in vision and is one of the retinal proteins capable of inducing an inflammatory eye disease called experimental autoimmune uveitis. These studies therefore demonstrate an important role for this lymphokine, that is, the enhanced expression of a neuronal cell protein. This finding may also identify additional mechanisms by which IFN-gamma may participate in immunopathologic events in nervous tissue.

Blood-retinal barrier breakdown in experimental coronavirus retinopathy: association with viral antigen, inflammation, and VEGF in sensitive and resistant strains.

Intraocular coronavirus inoculation results in a biphasic retinal disease in susceptible mice (BALB/c) characterized by an acute inflammatory response, followed by retinal degeneration associated with autoimmune reactivity. Resistant mice (CD-1), when similarly inoculated, only develop the early phase of the disease. Blood-retinal barrier (BRB) breakdown occurs in the early phase in both strains, coincident with the onset of inflammation. As the inflammation subsides, the extent of retinal vascular leakage is decreased, indicating that BRB breakdown in experimental coronavirus retinopathy (ECOR) is primarily due to inflammation rather than to retinal cell destruction. Vascular endothelial growth factor (VEGF) is upregulated only in susceptible mice during the secondary (retinal degeneration) phase.

Identification of the lymphokines, interferon-gamma and interleukin-2, in inflammatory eye diseases.

The exact pathogenic mechanisms involved in autoimmune and inflammatory eye diseases are not known. However, studies during the past few years indicate that a T cell infiltrate, T cell sensitization to retinal antigens and expression of major histocompatibility complex (MHC) class II antigens are associated with this process. In this report we show that the lymphokines, IL-2 and IFN-gamma, are present in the human eye during inflammatory and autoimmune diseases. The presence of these lymphokines is associated with a lymphocyte infiltrate, predominantly of T cell origin, and with the expression of MHC class II antigens on both the infiltrating cells and ocular resident cells, that is, retinal pigment epithelial (rpe) cells and retinal vascular endothelial cells. Furthermore, in vitro studies demonstrate that IFN-gamma can enhance the expression of the HLA-DR determinant on both of these cell types. These observations suggest that lymphokine induced class II antigen expression may serve as a local amplification system in autoimmune and inflammatory eye diseases. A better understanding of the role of lymphokines in the mechanisms involved in the development of autoimmunity and inflammation may be beneficial in the treatment of these diseases.

Ocular tropisms of murine coronavirus (strain JHM) after inoculation by various routes.

The coronavirus mouse hepatitis virus (MHV, strain JHM) infects tissues in the anterior and posterior segments when injected intravitreally into adult mouse eyes. Infection causes progressive damage to the photoreceptors and retinal pigment epithelium (RPE), resulting in a disease the authors have termed JHM retinopathy. To determine whether this virus is retinotropic independent of route of inoculation, the authors injected mice with virus by several different routes: into the anterior chamber (AC), onto the cornea, intranasally, or intracerebrally. Inoculation into the AC produced effects similar to those after intravitreal inoculation, although slightly slower in onset. Viral antigen was detected in the anterior portion of the iris on day 3, and by day 6, was also located primarily in the inner nuclear layer, photoreceptors, Müller cells, and RPE. However, by day 10, viral antigens were only detected in a few cells in the ganglion cell layer. Infectious virus was isolated from neural retinas on days 3 and 6, but not on day 10. In contrast, infectious virus could not be isolated from contralateral eyes. After 14 weeks, specific regions of some retinas were atrophied, with most of the retinal layers involved. Inoculation by other routes also resulted in virus-induced disease. Scarification of the cornea with virus, but not application of virus droplets alone, caused pathologic changes in the corneal epithelium and stroma and subtle effects on the ganglion cell and inner plexiform layers. Intracerebral inoculation of virus affected mainly the RPE. Pathologic effects and viral antigens were not detected in eyes from four mice inoculated intranasally. These results show that a murine coronavirus is retinotropic when introduced by several direct routes and one indirect route. Moreover, these studies show that long-lasting retinal disorders ranging in intensity from mild to severe can occur after coronavirus infection.

Genetic predisposition to coronavirus-induced retinal disease.

PURPOSE: Retinal inflammatory and degenerative processes in humans and animals frequently are associated with genetic factors. The murine coronavirus, mouse hepatitis virus (MHV), JHM strain, induces a biphasic retinal disease in adult BALB/c mice. The genetic constitution of the host and the virus serotype can be critical factors in determining the outcome of a virus infection. The purpose of this study was to evaluate the possible role of host genetics in murine coronavirus-induced retinal disease. METHODS: JHM virus was inoculated by the intravitreal route into BALB/c, CD-1, and A/J mice. At varying times after inoculation, eye tissues were evaluated histologically. Antibody responses to the virus were evaluated by neutralization assays. RESULTS: JHM virus induces a biphasic retinal disease in BALB/c mice. In the early phase, 1 to 7 days after inoculation, retinal vasculitis is observed. The second phase, characterized by retinal degeneration in the absence of inflammation, is seen by day 10 and progresses for several months. There is a similar biphasic disease process in JHM virus-infected A/J mice. However, retinal changes are less severe than those seen in BALB/c mice. Retinal tissue damage induced by JHM virus in CD-1 mice is different. Only the early phase of the disease, consisting of retinal vasculitis, was observed. These CD-1 mice do not develop the retinal degenerative disease. In fact, after day 10, the retina has a normal appearance. These differences in retinal tissue damage are seen over a wide range of infectivity of the virus inocula. Virus concentrations ranging from 10(1.4) to 10(4.4) TCID50/5 microliters were capable of inducing both inflammation and degeneration in BALB/c mice, whereas, the highest concentration of virus (10(4.4) TCID50/5 microliters) in CD-1 mice resulted in only the early inflammatory changes. CONCLUSIONS: The authors show that the genetics of the host can profoundly affect the nature of retinal tissue damage. These studies substantiate the concept that a virus can indeed trigger retinal degenerative processes in genetically susceptible hosts.

Development and characterization of monoclonal antibodies directed against the retinal pigment epithelial cell.

The retinal pigment epithelium consists of a unicellular layer of neuroepithelial cells that are essential for the maintenance of normal function of the neural retina. In order to evaluate more critically this cell in health and disease, we prepared monoclonal antibodies against human retinal pigment epithelial (RPE) cells. Balb/c mice were immunized with human RPE cells. Spleen cells were fused with myeloma cells and resultant hybridomas were selected for antibody production. Supernatants were assayed by immunoperoxidase on frozen sections of human eye tissues. Two hybrids were cloned and ascites were generated in mice. These IgG antibodies react only with RPE cells and show no cross-reactivity with other cells in the eye or with human brain, kidney, skin, salivary glands, lymphocytes or monocytes. These antibodies recognize cell surface molecules that are highly conserved since they can be found in man, monkey, rat, cow, chicken and frog. SDS gel electrophoresis and immunoblot analysis showed that one of the antibodies reacted with a 42,000 MW polypeptide. Evaluation of the developing rat retina revealed that the epitopes are not detected at birth, are weakly present at day 6 and are highly recognized by day 9. These immunoglobulins will allow us to evaluate RPE cells in disease (proliferation, migration) and to probe the bioregulatory functions (phagocytosis, vitamin A transport) of these cells.

Modulation of major histocompatibility complex class 1 genes in human retinoblastoma cells by interferons.

PURPOSE: To examine the mechanism(s) of interferon (IFN) induced expression of major histocompatibility complex (MHC) class 1 molecules on the human retinoblastoma cell line, Y-79. METHODS: Y-79 cells were incubated in the presence of IFN-alpha, -beta, and -gamma. Y-79 cell expression of MHC class 1 molecules was measured by flow cytometric analysis. HLA-B7 and oncogene transcription were evaluated by Northern blot analysis and nuclear runoff transcription assays. RESULTS: IFN-gamma increased MHC-class 1 antigen expression and induced a fivefold increase in its transcription rate. Posttranscriptionally, IFN-beta and -gamma increased steady state messenger RNA for the HLA-B7 gene. These effects were not associated with down regulation of N-myc oncogene nuclear transcription. Moreover, dexamethasone did not affect the IFN-gamma induced expression of MHC-class 1 molecules. CONCLUSIONS: Both transcriptional and posttranscriptional mechanisms are implicated in the modulation of class 1 molecule expression by IFN. In addition, this modulation is not associated with down regulation of N-myc oncogene expression. Spontaneous or IFN-gamma induced MHC class 1 antigen expression in retinoblastoma Y-79 cells is resistant to glucocorticoid hormones.

Cytokine-induced modulation of cellular proteins in retinoblastoma. Analysis by flow cytometry.

Cytokines are a group of specialized, hormone-like proteins that can exert profound influences on cellular development and on a variety of cellular functions. Retinoblastoma cells are an important model for exploring human malignancy and differentiation. These multipotent embryonic cells are capable of differentiating into neuronal, glial-like and retinal pigment epithelium (RPE)-like elements. This report shows that flow cytometric analysis can be used to measure the expression of both cytoplasmic and cell surface proteins in retinoblastoma cells. The authors used this technique to monitor changes in the expression of selected cellular proteins after exposure to specific cytokines and found that MHC class I molecules were augmented by interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma), but not by tumor necrosis factor (TNF). However, the MHC class II molecules were augmented by IFN-gamma but not by IFN-alpha or TNF. The neuronal markers, IRBP and PR-6, the glial-like marker, GFAP, and the RPE cell markers, RPE-9 and RPE-15, were not altered by any of the cytokines tested. Furthermore, IFN-gamma induced a striking enhancement of the expression of the photoreceptor cell protein, S-antigen. In contrast, IFN-alpha and TNF did not affect the expression of S-antigen. These studies show that the cytokine, IFN-gamma, can enhance a distinct cellular protein associated with cells committed to a specific cell lineage.

The role of apoptosis within the retina of coronavirus-infected mice.

PURPOSE: To evaluate the possible roles of apoptosis in the murine retinopathy induced by coronavirus. METHODS: Mice were inoculated with virus intravitreally. Mouse eyes harvested at varying times after inoculation were evaluated for apoptotic and immunologic events by hematoxylin and eosin staining, immunohistochemical staining, in situ terminal deoxynucleotidyltransferase dUTP nick-end labeling (TUNEL) assay, and electron microscopy. Isolated retinas were analyzed for infectious virus and for expression of apoptosis-associated genes. RESULTS: The number of apoptotic events was significantly elevated in infected eyes from BALB/c and CD-1 mouse strains, reaching a maximum at days 6 through 10, and returning to normal levels at day 20. The majority of apoptotic cells were observed in the outer nuclear layer of the infected retina. In contrast, few apoptotic cells were observed in normal or mock-injected mouse eyes. Apoptotic events within the retina were associated with the presence of viral antigen, infiltration of CD8(+) T cells, and clearance of infectious virus. Reverse transcription-polymerase chain reaction (RT-PCR) analysis identified the upregulation of Fas ligand (FasL) and granzyme B mRNAs within the infected retinas. The development of apoptosis, regulative gene expression, and viral clearance were similar in both retinal degeneration-susceptible (BALB/c) and -resistant (CD-1) mice. CONCLUSIONS: Retinal apoptosis was associated with retinal inflammation, a decrease in infectious virus, and upregulation of genes associated with CTL killing. These studies indicate that retinal apoptosis may be one of the host mechanisms that contribute to limiting this retinal infection.

Cytomegalovirus replication in human retinal pigment epithelial cells. Altered expression of viral early proteins.

PURPOSE: Cytomegalovirus (CMV) infections are frequent complications in patients who have undergone kidney and bone marrow transplant and in patients with acquired immune deficiency syndrome. The mechanism by which CMV is activated and replicated within the retina is unknown. The authors evaluated the ability of human CMV to initiate replication in human retinal pigment epithelial (RPE) cells and compared this system with CMV replication in human fibroblasts (HEL-299, MRC-5) and human amnion epithelial (WISH) cells. METHODS: Human RPE cells were obtained from donor eyes and propagated in vitro. Cells were infected, and CMV replication was evaluated in three ways: the detection of viral antigen by immunofluorescent, flow cytometry, and Western blot assays; the detection of virus-induced cytopathic effect (cpe), and the detection of infectious virus. RESULTS: No evidence of viral replication in the epithelial (WISH) cells was found. Although CMV does not usually replicate in vitro in epithelial cells, CMV replication was detected in RPE cells. There are a number of distinct differences in CMV replication in RPE cells compared to replication in human fibroblasts. Virus-induced cpe and the production of infectious virus by RPE cells were delayed when compared to virus infection in either HEL or MRC 5 cells. At a multiplicity of infection of 0.1 and 1, cpe and infectious virus yield reached maximum levels at days 4 to 5 in fibroblasts and at days 19 to 46 in RPE cells, respectively. Nevertheless, infectious virus produced by RPE cells (10(6.5) TCID50/0.1 ml) significantly surpassed levels produced by HEL cells (10(5.5)TCID50/0.1 ml). The permissive infection in RPE cells consisted of a prolonged period (5 to 6 days) of virus production in the absence of cytopathology. Virus protein expression evaluated by indirect immunofluorescence assays, Western blot analysis, and flow cytometry revealed a delay in viral protein expression in RPE cells compared to viral protein expression in fibroblasts. The pattern of viral protein evaluated by flow cytometry was noticeably different in the two cell types. At the middle phase of CMV replication in RPE cells, a low percentage of cells express immediate early (IE) protein at a time when a high percentage of the cells express early (E) proteins. This IE-1 protein is a stable protein found concurrently with E protein in fibroblasts. This difference in percentage of cells expressing specific CMV proteins is transient, that is, it does not remain apparent at 100% cpe. CONCLUSIONS: Retinal pigment epithelial cells appear to demonstrate a distinct pattern of CMV infection. The low frequency of expression of IE viral protein in RPE cells, the subsequent slow replication of CMV, and the altered expression of IE viral proteins may be critical variables that impact on their relationship to viral persistence and activation within the retina. Alterations in the IE gene product may indicate the existence of positive or negative nuclear transcription factors within infected RPE cells.

Redistribution and reduction of interphotoreceptor retinoid-binding protein during ocular coronavirus infection.

Inoculation of the neurotropic coronavirus mouse hepatitis virus strain JHM intravitreally or into the anterior chamber causes acute infection of the retinal pigment epithelium (RPE) and neural retina. Weeks later, many retinas have foci of moderate to severe atrophy. The effect of coronavirus infection (after intravitreal inoculation) was examined on interphotoreceptor retinoid-binding protein (IRBP), the glycolipoprotein in the interphotoreceptor matrix (IPM) thought to transport retinoids between the photoreceptors and the RPE. Changes in IRBP distribution accompanied virus-associated retinal pathology, including photoreceptor loss and RPE abnormalities. Immunohistochemistry on days 3 and 6 showed that IRBP had diffused into the neural retina away from the IPM. The IRBP became localized abnormally in the same areas as virus-induced lesions, shown by staining adjacent sections with a monoclonal antibody specific for the viral nucleocapsid protein. Moreover, the level of IRBP in isolated retinas, measured in an immunoslot-blot assay, decreased significantly by day 3 and remained low through day 23. This decrease was confirmed in eyecups isolated on day 6. It may be caused in part by loss of photoreceptors and diffusion of IRBP through the retina into the vitreous. These studies show that a virus may induce an acute, limited infection in the retina that can be cleared by the host. However, the infection initiated a series of events resulting in long-term reduction and redistribution of a critical photoreceptor protein.

Cyclooxygenase-2 gene expression and regulation in human retinal pigment epithelial cells.

PURPOSE: Cyclooxygenases (COX) orchestrate a variety of homeostatic processes and participate in various pathophysiological conditions. The retinal pigment epithelium (RPE) cell performs a variety of regulatory functions within the retina. The conditions under which COX-1 and COX-2 are expressed and upregulated in human RPE (HRPE) cells were determined. METHODS: COX gene expression was examined using RT-PCR analysis of untreated HRPE cultures or cultures exposed to bacterial lipopolysaccharide or various cytokines. COX proteins were detected by immunohistochemistry and Western blot analysis. Prostaglandin (PG) production was analyzed by EIA. RESULTS: Examination of untreated RPE cells revealed the presence of COX-2 mRNA and the absence of COX-1 mRNA. Moreover, cytokine stimulation more readily enhanced COX-2 gene expression than COX-1 gene expression. IL-1 beta, the most potent inducer of COX-2, also resulted in detection of COX-2 protein by immunocytochemical staining and Western blot analysis. There was a direct relationship between both the appearance and amount of COX-2 mRNA and protein synthesis and the degree of PG synthesis by RPE cells. Furthermore, COX inhibitors significantly decreased PG production. Pretreatment of RPE cells with a NF-kappa B inhibitor, PDTC, resulted in dose-dependent decrease in IL-1 beta-induced COX-2 gene expression and PG production. CONCLUSIONS: COX-2 was the predominant isoform of cyclooxygenase in untreated HRPE cells. When HRPE cells were treated with proinflammatory cytokines, COX-2 gene expression and synthesis of PGs were enhanced. NF-kappa B mediated the induction of COX-2 gene expression in HRPE cells. These studies indicate that RPE cells may participate in normal and pathologic retinal conditions through the induction of COX-2.

Inhibition of human cytomegalovirus replication in a human retinal epithelial cell model by antisense oligonucleotides.

PURPOSE: The antiviral activity of first and second generation antisense oligonucleotides on human cytomegalovirus (CMV) replication was evaluated in two cell systems, the traditional system on human fibroblasts and on human retinal pigment epithelial (HRPE) cell culture system. METHODS: To evaluate CMV replication strategies within the retina, an HRPE cell system permissive to CMV replication was developed. In this study, the antiviral activity of the antisense oligonucleotides, ISIS 2922 (Vitraven) and ISIS 13312, was evaluated in the traditional fibroblast antiviral assay and in the HRPE cell system. Antiviral activity was measured by evaluating inhibition of virus induced cytopathic effect, virus plaque formation, and virus gene expression. RESULTS: Both oligonucleotides produced concentration-dependent inhibition of CMV cytopathic effect and CMV plaque formation in both human RPE cells and a human fibroblast cell line, MRC-5. The oligonucleotide, ISIS 2922, demonstrated a mean 50% inhibitory concentration (IC(50)) of 0.04 and 0.24 microM in HRPE and MRC-5 cells, respectively. The second-generation oligonucleotide, ISIS 13312, yielded similar results with IC(50) levels of 0.05 and 0.3 microM in HRPE and MRC-5 cells, respectively. Similar findings were obtained with a CMV clinical isolate. In addition, initiation of effective oligonucleotide treatment could be introduced 6 days after CMV infection in HRPE cells, whereas, in the fibroblast cell line, oligonucleotide treatment was only effective up to 3 days after infection. Semiquantitative RT-PCR analysis demonstrated significant inhibition of CMV intermediate early and late mRNAs by both oligonucleotides. CONCLUSIONS: These studies demonstrate that HRPE cells were significantly more sensitive than fibroblasts to the antiviral actions of ISIS 2922 and ISIS 13312. Moreover, the data indicate that the anti-CMV potency of the two oligonucleotides was similar. The enhanced potency of these oligonucleotides in HRPE cells may be associated with a delay in viral gene transcription and slow viral replication and spread in these cells.

HLA-DR antigens on retinal pigment epithelial cells from patients with uveitis.

The pathogenic mechanisms involved in immunologically associated ocular diseases are not clearly understood. To further evaluate these types of disorders, we examined the expression of HLA-DR antigen on eye sections from normal individuals and five patients (six eyes) with ocular inflammation (sympathetic ophthalmia and chronic uveitis). Using immunoperoxidase staining technique and the complement-mediated cytotoxicity assay, we detected the presence of HLA-DR antigens on retinal pigment epithelial (RPE) cells from uveitic eyes. In contrast, HLA-DR antigen was not detected on RPE cells from normal ocular tissue. Our study shows that during the course of human ocular inflammatory disorders, the RPE cell is activated to express HLA-DR antigens. This antigen expression may be important in the initiation and/or perpetuation of immune reactivity in the eye.

Novel adjuvant strategies for experimental malaria and AIDS vaccines.

Adjuvant research has improved the ability of biotechnology to generate novel vaccines. Numerous strategies for enhancing the immunogenicity of synthetic peptides and proteins have been identified. This overview focuses on adjuvant development and vaccine delivery systems that provide new tools for amplifying the effectiveness of ongoing malaria and AIDS vaccine development programs. In addition, some of the complex challenges and issues that have become associated with the delivery of modern vaccines in man are outlined. As adjuvant research continues to open new opportunities in vaccine development, there is renewed expectation that further generations of safe and potent vaccines will be possible against a broad spectrum of infectious agents and cancer.

Expression of HLA-DR antigen on retinal pigment epithelial cells in retinitis pigmentosa.

Class II (HLA-DR) antigens are cell surface molecules that play a major role in the initiation and perpetuation of immune responses. Although most cells do not constitutively express class II antigens, selected cells can be stimulated to do so in some immunologically mediated disorders. When retinal pigment epithelial cells were evaluated by either immunoperoxidase or immunofluorescent staining of frozen eye sections from normal individuals, HLA-DR antigens were not detected. In contrast, retinal pigment epithelial cells from two patients with retinitis pigmentosa did express HLA-DR antigens. These findings demonstrated that at some time during the course of retinitis pigmentosa, the retinal pigment epithelial cell is activated to express HLA-DR.

Characterization of primate antibody responses to administered murine monoclonal immunoglobulin.

Murine monoclonal antibodies (MAb) are currently being assessed for their utility as tools in cancer management. Anti-murine immunoglobulin responses have been observed in many patients receiving monoclonal antibody treatment. In this study, we evaluated the response of primates to the administration of a monoclonal antibody. MAb B6.2, an antibody generated against a human breast tumor metastasis, was used as a prototype MAb. Baboons were inoculated with MAb B6.2 whole IgG, Fab', or F(ab')2 fragments. Blood samples were drawn at periodic intervals post-inoculation and the sera collected. Anti-murine immunoglobulin responses were detected using a solid-phase radioimmunoassay. The specificity of the antibody response was analyzed to determine if the response was directed against the species of origin of the MAb (species specificity), against the class of the MAb (isotype specificity), or against the hypervariable region of the MAb (idiotype specificity). We found that primates develop a humoral immune response against all three forms of the monoclonal antibody [IgG, Fab', and F(ab')2]. Furthermore, this antibody response demonstrated a high degree of specificity for the antigen binding site suggesting an idiotypic specificity. Using a competitive radioimmunoassay, the antibody response was found to interfere with antigen binding of MAb B6.2. These studies suggest that monoclonal antibody treatment can generate an anti-idiotypic response which may alter the efficacy of this mode of treatment.