Spatiotemporal immune zonation of the human kidney

Tissue-resident immune cells are important for organ homeostasis and defense. The epithelium may contribute to these functions directly or by cross-talk with immune cells. We used single-cell RNA sequencing to resolve the spatiotemporal immune topology of the human kidney. We reveal anatomically defined expression patterns of immune genes within the epithelial compartment, with antimicrobial peptide transcripts evident in pelvic epithelium in the mature, but not fetal, kidney. A network of tissue-resident myeloid and lymphoid immune cells was evident in both fetal and mature kidney, with postnatal acquisition of transcriptional programs that promote infection-defense capabilities. Epithelial-immune cross-talk orchestrated localization of antibacterial macrophages and neutrophils to the regions of the kidney most susceptible to infection. Overall, our study provides a global overview of how the immune landscape of the human kidney is zonated to counter the dominant immunological challenge.

A KLF6-driven transcriptional network links lipid homeostasis and tumour growth in renal carcinoma

Transcriptional networks are critical for the establishment of tissue-specific cellular states in health and disease, including cancer. Yet, the transcriptional circuits that control carcinogenesis remain poorly understood. Here we report that Kruppel like factor 6 (KLF6), a transcription factor of the zinc finger family, regulates lipid homeostasis in clear cell renal cell carcinoma (ccRCC). We show that KLF6 supports the expression of lipid metabolism genes and promotes the expression of PDGFB, which activates mTOR signalling and the downstream lipid metabolism regulators SREBF1 and SREBF2. KLF6 expression is driven by a robust super enhancer that integrates signals from multiple pathways, including the ccRCC-initiating VHL-HIF2A pathway. These results suggest an underlying mechanism for high mTOR activity in ccRCC cells. More generally, the link between super enhancer-driven transcriptional networks and essential metabolic pathways may provide clues to the mechanisms that maintain the stability of cell identity-defining transcriptional programmes in cancer.

Super enhancers are frequently involved in the dysregulation of gene expression in cancer. Here, in kidney cancer, a super enhancer is shown to drive the expression of KLF6, which alters the expression of lipid metabolism genes and promotes tumorigenesis.

Enhanced detection of circulating tumor DNA by fragment size analysis

Existing methods to improve detection of circulating tumor DNA (ctDNA) have focused on genomic alterations but have rarely considered the biological properties of plasma cell-free DNA (cfDNA). We hypothesized that differences in fragment lengths of circulating DNA could be exploited to enhance sensitivity for detecting the presence of ctDNA and for noninvasive genomic analysis of cancer. We surveyed ctDNA fragment sizes in 344 plasma samples from 200 patients with cancer using low-pass whole-genome sequencing (0.4×). To establish the size distribution of mutant ctDNA, tumor-guided personalized deep sequencing was performed in 19 patients. We detected enrichment of ctDNA in fragment sizes between 90 and 150 bp and developed methods for in vitro and in silico size selection of these fragments. Selecting fragments between 90 and 150 bp improved detection of tumor DNA, with more than twofold median enrichment in >95% of cases and more than fourfold enrichment in >10% of cases. Analysis of size-selected cfDNA identified clinically actionable mutations and copy number alterations that were otherwise not detected. Identification of plasma samples from patients with advanced cancer was improved by predictive models integrating fragment length and copy number analysis of cfDNA, with area under the curve (AUC) >0.99 compared to AUC <0.80 without fragmentation features. Increased identification of cfDNA from patients with glioma, renal, and pancreatic cancer was achieved with AUC > 0.91 compared to AUC < 0.5 without fragmentation features. Fragment size analysis and selective sequencing of specific fragment sizes can boost ctDNA detection and could complement or provide an alternative to deeper sequencing of cfDNA.

Single-cell transcriptomes from human kidneys reveal the cellular identity of renal tumors

Messenger RNA encodes cellular function and phenotype. In the context of human cancer, it defines the identities of malignant cells and the diversity of tumor tissue. We studied 72,501 single-cell transcriptomes of human renal tumors and normal tissue from fetal, pediatric, and adult kidneys. We matched childhood Wilms tumor with specific fetal cell types, thus providing evidence for the hypothesis that Wilms tumor cells are aberrant fetal cells. In adult renal cell carcinoma, we identified a canonical cancer transcriptome that matched a little-known subtype of proximal convoluted tubular cell. Analyses of the tumor composition defined cancer-associated normal cells and delineated a complex vascular endothelial growth factor (VEGF) signaling circuit. Our findings reveal the precise cellular identities and compositions of human kidney tumors.

NF-κB-Dependent Lymphoid Enhancer Co-option Promotes Renal Carcinoma Metastasis

Metastases, the spread of cancer cells to distant organs, cause the majority of cancer-related deaths. Few metastasis-specific driver mutations have been identified, suggesting aberrant gene regulation as a source of metastatic traits. However, how metastatic gene expression programs arise is poorly understood. Here, using human-derived metastasis models of renal cancer, we identify transcriptional enhancers that promote metastatic carcinoma progression. Specific enhancers and enhancer clusters are activated in metastatic cancer cell populations, and the associated gene expression patterns are predictive of poor patient outcome in clinical samples. We find that the renal cancer metastasis-associated enhancer complement consists of multiple coactivated tissue-specific enhancer modules. Specifically, we identify and functionally characterize a coregulatory enhancer cluster, activated by the renal cancer driver HIF2A and an NF-κB-driven lymphoid element, as a mediator of metastasis in vivo We conclude that oncogenic pathways can acquire metastatic phenotypes through cross-lineage co-option of physiologic epigenetic enhancer states.Significance: Renal cancer is associated with significant mortality due to metastasis. We show that in metastatic renal cancer, functionally important metastasis genes are activated via co-option of gene regulatory enhancer modules from distant developmental lineages, thus providing clues to the origins of metastatic cancer. Cancer Discov; 8(7); 850-65. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 781.

Whole blood mRNA in prostate cancer reveals a four-gene androgen regulated panel

Due to increased sensitivity, the expression of circulating nucleotides is rapidly gaining popularity in cancer diagnosis. Whole blood mRNA has been used in studies on a number of cancers, most notably two separate studies that used whole blood mRNA to define non-overlapping signatures of prostate cancer that has become castration independent. Prostate cancer is known to rely on androgens for initial growth, and there is increasing evidence on the importance of the androgen axis in advanced disease. Using whole blood mRNA samples from patients with prostate cancer, we have identified the four-gene panel of FAM129A, MME, KRT7 and SOD2 in circulating mRNA that are differentially expressed in a discovery cohort of metastatic samples. Validation of these genes at the mRNA and protein level was undertaken in additional cohorts defined by risk of relapse following surgery and hormone status. All the four genes were downregulated at the mRNA level in the circulation and in primary tissue, but this was not always reflected in tissue protein expression. MME demonstrated significant differences in the hormone cohorts, whereas FAM129A is downregulated at the mRNA level but is raised at the protein level in tumours. Using published ChIP-seq data, we have demonstrated that this may be due to AR binding at the FAM129A and MME loci in multiple cell lines. These data suggest that whole blood mRNA of androgen-regulated genes has the potential to be used for diagnosis and monitoring of prostate cancer.

A new explanation for recessive myotonia congenita: exon deletions and duplications in CLCN1

OBJECTIVE

To assess whether exon deletions or duplications in CLCN1 are associated with recessive myotonia congenita (MC).

METHODS

We performed detailed clinical and electrophysiologic characterization in 60 patients with phenotypes consistent with MC. DNA sequencing of CLCN1 followed by multiplex ligation-dependent probe amplification to screen for exon copy number variation was undertaken in all patients.

RESULTS

Exon deletions or duplications in CLCN1 were identified in 6% of patients with MC. Half had heterozygous exonic rearrangements. The other 2 patients (50%), with severe disabling infantile onset myotonia, were identified with both a homozygous mutation, Pro744Thr, which functional electrophysiology studies suggested was nonpathogenic, and a triplication/homozygous duplication involving exons 8-14, suggesting an explanation for the severe phenotype.

CONCLUSIONS

These data indicate that copy number variation in CLCN1 may be an important cause of recessive MC. Our observations suggest that it is important to check for exon deletions and duplications as part of the genetic analysis of patients with recessive MC, especially in patients in whom sequencing identifies no mutations or only a single recessive mutation. These results also indicate that additional, as yet unidentified, genetic mechanisms account for cases not currently explained by either CLCN1 point mutations or exonic deletions or duplications.

The rs10993994 risk allele for prostate cancer results in clinically relevant changes in microseminoprotein-beta expression in tissue and urine

Background

Microseminoprotein-beta (MSMB) regulates apoptosis and using genome-wide association studies the rs10993994 single nucleotide polymorphism in the MSMB promoter has been linked to an increased risk of developing prostate cancer. The promoter location of the risk allele, and its ability to reduce promoter activity, suggested that the rs10993994 risk allele could result in lowered MSMB in benign tissue leading to increased prostate cancer risk.

Methodology/Principal Findings

MSMB expression in benign and malignant prostate tissue was examined using immunohistochemistry and compared with the rs10993994 genotype. Urinary MSMB concentrations were determined by ELISA and correlated with urinary PSA, the presence or absence of cancer, rs10993994 genotype and age of onset. MSMB levels in prostate tissue and urine were greatly reduced with tumourigenesis. Urinary MSMB was better than urinary PSA at differentiating men with prostate cancer at all Gleason grades. The high risk allele was associated with heterogeneity of MSMB staining and loss of MSMB in both tissue and urine in benign prostate.

Conclusions

These data show that some high risk alleles discovered using genome-wide association studies produce phenotypic effects with potential clinical utility. We provide the first link between a low penetrance polymorphism for prostate cancer and a potential test in human tissue and bodily fluids. There is potential to develop tissue and urinary MSMB for a biomarker of prostate cancer risk, diagnosis and disease monitoring.

Tumor necrosis factor receptor expression and signaling in renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC), a tubular epithelial cell (TEC) malignancy, frequently secretes tumor necrosis factor (TNF). TNF signals via two distinct receptors (TNFRs). TNFR1, expressed in normal kidney primarily on endothelial cells, activates apoptotic signaling kinase 1 and nuclear factor-kappaB (NF-kappaB) and induces cell death, whereas TNFR2, inducibly expressed on endothelial cells and on TECs by injury, activates endothelial/epithelial tyrosine kinase (Etk), which trans-activates vascular endothelial growth factor receptor 2 (VEGFR2) to promote cell proliferation. We investigated TNFR expression in clinical samples and function in short-term organ cultures of ccRCC tissue treated with wild-type TNF or specific muteins selective for TNFR1 (R1-TNF) or TNFR2 (R2-TNF). There is a significant increase in TNFR2 but not TNFR1 expression on malignant TECs that correlates with increasing malignant grade. In ccRCC organ cultures, R1-TNF increases TNFR1, activates apoptotic signaling kinase and NF-kappaB, and promotes apoptosis in malignant TECs. R2-TNF increases TNFR2, activates NF-kappaB, Etk, and VEGFR2 and increases entry into the cell cycle. Wild-type TNF induces both sets of responses. R2-TNF actions are blocked by pretreatment with a VEGFR2 kinase inhibitor. We conclude that TNF, acting through TNFR2, is an autocrine growth factor for ccRCC acting via Etk-VEGFR2 cross-talk, insights that may provide a more effective therapeutic approach to this disease.

Hybrid ICA-Bayesian network approach reveals distinct effective connectivity differences in schizophrenia

We utilized a discrete dynamic Bayesian network (dDBN) approach (Burge, J., Lane, T., Link, H., Qiu, S., Clark, V.P., 2007. Discrete dynamic Bayesian network analysis of fMRI data. Hum Brain Mapp.) to determine differences in brain regions between patients with schizophrenia and healthy controls on a measure of effective connectivity, termed the approximate conditional likelihood score (ACL) (Burge, J., Lane, T., 2005. Learning Class-Discriminative Dynamic Bayesian Networks. Proceedings of the International Conference on Machine Learning, Bonn, Germany, pp. 97-104.). The ACL score represents a class-discriminative measure of effective connectivity by measuring the relative likelihood of the correlation between brain regions in one group versus another. The algorithm is capable of finding non-linear relationships between brain regions because it uses discrete rather than continuous values and attempts to model temporal relationships with a first-order Markov and stationary assumption constraint (Papoulis, A., 1991. Probability, random variables, and stochastic processes. McGraw-Hill, New York.). Since Bayesian networks are overly sensitive to noisy data, we introduced an independent component analysis (ICA) filtering approach that attempted to reduce the noise found in fMRI data by unmixing the raw datasets into a set of independent spatial component maps. Components that represented noise were removed and the remaining components reconstructed into the dimensions of the original fMRI datasets. We applied the dDBN algorithm to a group of 35 patients with schizophrenia and 35 matched healthy controls using an ICA filtered and unfiltered approach. We determined that filtering the data significantly improved the magnitude of the ACL score. Patients showed the greatest ACL scores in several regions, most markedly the cerebellar vermis and hemispheres. Our findings suggest that schizophrenia patients exhibit weaker connectivity than healthy controls in multiple regions, including bilateral temporal, frontal, and cerebellar regions during an auditory paradigm.

V-Lab-a virtual laboratory for autonomous agents-SLA-based learning controllers

In this paper, we present the use of stochastic learning automata (SLA) in multiagent robotics. In order to fully utilize and implement learning control algorithms in the control of multiagent robotics, an environment for simulation has to be first created. A virtual laboratory for simulation of autonomous agents, called V-Lab is described. The V-Lab architecture can incorporate various models of the environment as well as the agent being trained. A case study to demonstrate the use of SLA is presented.

The effect of catheter type and site on infection rates in total parenteral nutrition patients

Infections pose a major problem in patients receiving total parenteral nutrition. Controversy continues concerning the effect of catheter type (triple-, double-, single-lumen, or pulmonary artery), insertion site (subclavian, internal jugular, or femoral vein), and the incidence of catheter-related infections. We retrospectively studied multi-lumen catheter use for total parenteral nutrition over a 6-month period in 192 patients, a total of 3334 catheter days. Nonintensive care unit catheters were inserted by the Nutrition Support Service, and intensive care unit catheters were inserted by the intensive care unit staff. All catheters were cared for using Nutrition Support Service protocols, with multi-lumen catheters changed every 7 to 10 days and pulmonary artery catheters changed every 4 days. Infections were determined by semiquantitative cultures (> 15 colonies/plate). The incidence of infections for triple-lumen catheters was 5 (subclavian), 17 (internal jugular), and 36% (femoral) respectively; total infection rate for triple-lumen catheters was 10%. Infection rates for pulmonary artery catheters were 4 (subclavian), and 6% internal (jugular site), respectively, the overall infection rate was 5%. There were no differences in infection rates at any site based on catheter type; however, when triple-lumen catheter sites were compared, the differences were significant (p < .001 vs subclavian, chi 2). Catheter duration was 7.8 days (subclavian),, 7.3 days (internal jugular), and 4.6 (femoral) days. These data suggest that the use of multi-lumen catheters for total parenteral nutrition is safe, that there is a benefit associated with the subclavian route, and that the femoral site should be avoided.

Safety and efficacy of flestolol, a new ultrashort-acting beta-adrenergic blocking agent, for supraventricular tachyarrhythmias

Flestolol, a new ultrashort-acting (half-life 6.9 minutes) beta-blocking drug, was administered by intravenous infusion to 18 patients with new-onset atrial fibrillation or flutter and rapid ventricular response (120 beats/min or more for at least 30 minutes). Drug dose of flestolol was progressively increased until at least 1 of 3 endpoints was achieved: at least a 20% reduction in heart rate from baseline, heart rate 100 beats/min or less, or conversion to normal sinus rhythm. Flestolol was then administered as a maintenance infusion up to 24 hours. When flestolol was discontinued, patients were monitored for 1 additional hour. The mean ventricular response at baseline of 133 +/- 12 beats/min decreased to 103 +/- 20 beats/min at the end of flestolol titration (p less than 0.0001). Fourteen patients (78%) achieved defined endpoints. All 14 patients who continued to receive maintenance infusion had a sustained response. When flestolol was discontinued, ventricular response increased 33 +/- 23% within 60 minutes. The only adverse effect seen was hypotension in 2 patients. Flestolol is effective in slowing ventricular response in new-onset atrial fibrillation and flutter, maintains a therapeutic effect during continuous infusion and rapidly loses therapeutic effect when discontinued.

Tolerance and beta-adrenergic blocking activity of flestolol, a short-acting beta blocker

The tolerance and beta-adrenergic blocking activity of flestolol, a short-acting beta-blocker, was investigated in 30 subjects. Flestolol infused intravenously at doses up to 100 micrograms/kg/min was found to be well tolerated. A dose-dependent attenuation of isoproterenol-induced tachycardia and increase in systolic blood pressure occurred with flestolol at doses ranging from 0.5 to 15.0 micrograms/kg/min. The average percent reduction in isoproterenol-induced tachycardia (beta-blockade) at each dose of flestolol, 0.5, 2.5, 5.0, 15.0, and 50.0 micrograms/kg/min, was 15.1%, 45.9%, 67.0%, 85.9%, and 90.3%, respectively. The onset of beta-blockade occurred within 30 minutes. After the end of flestolol infusion there was a marked reduction in beta-blockade within 6 minutes, with complete recovery from beta-blockade within 30 to 45 minutes. There was a statistically significant (P less than 0.01) positive correlation between flestolol dosage and its blood levels (r = 0.91) as well as between the flestolol-induced beta-blockade and its dosage (r = 0.62).

Flestolol: an ultra-short-acting beta-adrenergic blocking agent

Flestolol (ACC-9089) is a nonselective, competitive, ultra-short-acting beta-adrenergic blocking agent, without any intrinsic sympathomimetic activity. Flestolol is metabolized by plasma esterases and has an elimination half-life of approximately 6.5 minutes. This agent was well tolerated in healthy volunteers at doses up to 100 micrograms/kg/min. In long-term infusion studies, flestolol was well tolerated at the effective beta-blocking dose (5 micrograms/kg/min) for up to seven days. Flestolol blood concentrations increased linearly with increasing dose and good correlation exists between blood concentrations of flestolol and beta-adrenergic blockade. Flestolol produced a dose-dependent attenuation of isoproterenol-induced tachycardia. Electrophysiologic and hemodynamic effects of flestolol are similar to those of other beta blockers. In contrast with other beta blockers, flestolol-induced effects reverse rapidly (within 30 minutes) following discontinuation because of its short half-life. Flestolol effectively reduced heart rate in patients with supraventricular tachyarrhythmia. In patients with unstable angina, flestolol infusion was found to be safe and effective in controlling chest pain. It is concluded that flestolol is a potent, well-tolerated, ultra-short-acting beta-adrenergic blocking agent. Use of flestolol in the critical care setting is currently undergoing investigation.

Dynamics of interaction between complement-fixing antibody/dsDNA immune complexes and erythrocytes. In vitro studies and potential general applications to clinical immune complex testing

Soluble antibody/3H-double-stranded PM2 DNA (dsDNA) immune complexes were briefly opsonized with complement and then allowed to bind to human erythrocytes (via complement receptors). The cells were washed and subsequently a volume of autologous blood in a variety of media was added, and the release of the bound immune complexes from the erythrocytes was studied as a function of temperature and time. After 1-2 h, the majority of the bound immune complexes were not released into the serum during blood clotting at either 37 degrees C or room temperature, but there was a considerably greater release of the immune complexes into the plasma of blood that was anticoagulated with EDTA. Similar results were obtained using various conditions of opsonization and also using complexes that contained lower molecular weight dsDNA. Thus, the kinetics of release of these antibody/dsDNA immune complexes differed substantially from the kinetics of release of antibody/bovine serum albumin complexes that was reported by others. Studies using the solution phase C1q immune complex binding assay confirmed that in approximately half of the SLE samples that were positive for immune complexes, there was a significantly higher level of detectable immune complexes in plasma vs. serum. Freshly drawn erythrocytes from some SLE patients exhibiting this plasma/serum discrepancy had IgG antigen on their surface that was released by incubation in EDTA plasma. Thus, the higher levels of immune complexes observed in EDTA plasma vs. serum using the C1q assay may often reflect the existence of immune complexes circulating in vivo bound to erythrocytes.

Suramin inhibits the binding of complement-fixing antibody/double-stranded DNA immune complexes to CR1

The effects of varying concentrations of heparin and suramin on the complement-mediated binding of antibody/double-stranded DNA immune complexes to red blood cells (RBCs) and Raji cells have been investigated. If the immune complexes are briefly opsonized with complement, suramin can block binding to both cell types, and heparin can block binding to RBCs. In addition, if these complexes are first allowed to bind to RBCs or Raji cells, relatively brief incubations in suramin are sufficient to cause release of the complexes from the cells' C3b receptors. The potential clinical and diagnostic implications of these findings are discussed.

The kinetics of [3H]-dsDNA/anti-DNA immune complex formation, binding by red blood cells, and release into serum: effect of DNA molecular weight and conditions of antibody excess

[3H]dsDNA/anti-DNA immune complexes (IC) formed, fixed complement, and bound rapidly to red blood cells (RBC) in whole blood (less than 5 min), but were released from the cells more slowly. The rate of release was dependent on both the antibody:DNA ratio and the m.w. of the DNA in the complex. For example, complexes formed with high m.w. DNA (6 X 10(6) daltons) were released more slowly (t1/2 = 60 min) than complexes formed with lower m.w. DNA (2 to 6 X 10(5) daltons, t1/2 = 15 to 20 min). The [3H]dsDNA/anti-DNA complexes, which were released from the cells as intact antigen/antibody/complement complexes, did not rebind to RBC, but did bind to Raji cells and could be precipitated by monoclonal antibody to C3d. When these released IC (RIC) containing high m.w. DNA were incubated with additional anti-DNA antibody and fresh complement, they rebound to RBC. However, RIC containing lower m.w. DNA (5 X 10(5) daltons) did not rebind to RBC under the same conditions. These data suggest that IC containing high m.w. DNA bind to and remain bound to RBC more effectively than IC containing lower m.w. DNA, and thus may be more easily cleared from the circulation by the RBC IC clearance mechanism. Thus, the size of the DNA in the IC may be a significant factor in the pathogenicity of DNA/anti-DNA complexes in SLE.

The kinetics of [3H]-dsDNA/anti-DNA immune complex formation, binding by red blood cells, and release into serum: effect of DNA molecular weight and conditions of antibody excess

[3H]dsDNA/anti-DNA immune complexes (IC) formed, fixed complement, and bound rapidly to red blood cells (RBC) in whole blood (less than 5 min), but were released from the cells more slowly. The rate of release was dependent on both the antibody:DNA ratio and the m.w. of the DNA in the complex. For example, complexes formed with high m.w. DNA (6 X 10(6) daltons) were released more slowly (t1/2 = 60 min) than complexes formed with lower m.w. DNA (2 to 6 X 10(5) daltons, t1/2 = 15 to 20 min). The [3H]dsDNA/anti-DNA complexes, which were released from the cells as intact antigen/antibody/complement complexes, did not rebind to RBC, but did bind to Raji cells and could be precipitated by monoclonal antibody to C3d. When these released IC (RIC) containing high m.w. DNA were incubated with additional anti-DNA antibody and fresh complement, they rebound to RBC. However, RIC containing lower m.w. DNA (5 X 10(5) daltons) did not rebind to RBC under the same conditions. These data suggest that IC containing high m.w. DNA bind to and remain bound to RBC more effectively than IC containing lower m.w. DNA, and thus may be more easily cleared from the circulation by the RBC IC clearance mechanism. Thus, the size of the DNA in the IC may be a significant factor in the pathogenicity of DNA/anti-DNA complexes in SLE.

The complement-mediated binding of soluble antibody/dsDNA immune complexes to human neutrophils

The complement-mediated binding of soluble antibody/3H-dsDNA immune complexes (prepared in vitro) to human polymorphonuclear leukocytes (PMN) has been investigated quantitatively. Studies with isolated complement components in conjunction with experiments on the binding of these complexes to human red blood cells suggest that the binding to both cell types is mediated predominantly by CR1 (C4b-C3b) receptors but that CR3 (iC3b or C3d-g) receptors may play a role in binding to PMN but probably not to RBC. Our results also indicate that under the standard conditions of these assays (37 degrees C, 20 to 40 min incubations) there is no significant internalization of the soluble antibody/dsDNA immune complexes after they are bound by the PMN.

The complement-mediated binding of soluble antibody/dsDNA immune complexes to human neutrophils

The complement-mediated binding of soluble antibody/3H-dsDNA immune complexes (prepared in vitro) to human polymorphonuclear leukocytes (PMN) has been investigated quantitatively. Studies with isolated complement components in conjunction with experiments on the binding of these complexes to human red blood cells suggest that the binding to both cell types is mediated predominantly by CR1 (C4b-C3b) receptors but that CR3 (iC3b or C3d-g) receptors may play a role in binding to PMN but probably not to RBC. Our results also indicate that under the standard conditions of these assays (37 degrees C, 20 to 40 min incubations) there is no significant internalization of the soluble antibody/dsDNA immune complexes after they are bound by the PMN.