Adjuvant Radiotherapy in Stage II Endometrial Cancer: Selective De-intensification of Adjuvant Treatment

AIMS

Risk stratification, including nodal assessment, allows for selective de-intensification of adjuvant radiotherapy in stage II endometrial cancer. Patterns of treatment and clinical outcomes, including the use of reduced volume 'mini-pelvis' radiotherapy fields, were evaluated in a population-based study.

MATERIALS AND METHODS

All patients diagnosed with pathological stage II endometrial cancer between 2000 and 2014, and received adjuvant radiotherapy in a regional healthcare jurisdiction were reviewed. Registry data were supplemented by a comprehensive review of patient demographics, disease characteristics and treatment details. The Charlson Comorbidity Score was calculated. Survival and recurrence data were analysed.

RESULTS

In total, 264 patients met the inclusion criteria. Most patients had endometrioid histology (83%); 41% of patients had International Federation of Gynecologists and Obstetricians grade 1 disease. Half (49%) had surgical nodal evaluation; 11% received chemotherapy. Most patients (59%) were treated with full pelvic radiotherapy fields ± brachytherapy. Seventeen per cent of patients received mini-pelvis radiotherapy ± brachytherapy, whereas 24% received brachytherapy alone. Five-year recurrence-free survival was 87% for the entire cohort, with no significant difference by adjuvant radiotherapy approach. Only one patient receiving mini-pelvis radiotherapy ± brachytherapy recurred in the pelvis but outside of the mini-pelvis field. Recorded late toxicity rates were highest for full pelvis radiotherapy + brachytherapy.

CONCLUSION

Risk stratification in a real-world setting allowed for selective de-intensification of adjuvant radiation with equivalent outcomes for stage II endometrial cancer. Mini-pelvis radiotherapy combined with brachytherapy is effective in highly selected patients, with the potential to decrease toxicity without compromising local control. Brachytherapy should be considered in low-risk stage II patients.

Building a network for multicenter, prospective research of central nervous system infections in South America: Process and lessons learned

Multicenter collaborative networks are essential for advancing research and improving clinical care for a variety of conditions. Research networks are particularly important for central nervous system infections, which remain difficult to study due to their sporadic occurrence and requirement for collection and testing of cerebrospinal fluid. Establishment of long-term research networks in resource-limited areas also facilitates diagnostic capacity building, surveillance for emerging pathogens, and provision of appropriate treatment where needed. We review our experience developing a research network for encephalitis among twelve hospitals in five Peruvian cities since 2009. We provide practical suggestions to aid other groups interested in advancing research on central nervous system infections in resource-limited areas.

Abstract 423: Cardiomyocyte-Specific Epidermal Growth Factor Receptor Deletion Differentially Alters Cardiac Contractility and Remodeling During Physiologic versus Pathologic Development

Epidermal Growth Factor Receptor (EGFR), a member of the Erbb receptor tyrosine kinase family, is essential to the development of multiple tissue and organs. Due to the embryonic lethality of global EGFR deletion, the impact of EGFR signaling in the adult heart, normally or in response to pathological stimuli, has not been well-explored. Using recently attained mice with floxed EGFR alleles crossed with αMHC-Cre mice, we have generated a cardiomyocyte-specific constitutive EGFR knockout mouse model (CM-EGFR KO) to address its role in the heart. Compared to their wild-type (WT) littermate controls, CM-EGFR-KO mice displayed age-related development of cardiac dysfunction and remodeling, occurring between 7 and 9 weeks of age, as monitored via echocardiography and immunohistochemistry analyses. Although contractile responsiveness to β-adrenergic receptor stimulation was unaffected by EGFR deletion, RNASeq analysis of CM-EGFR-KO hearts within this timeframe revealed alterations in myofilament protein expression profiles. Additionally, there was enhanced cardiomyocyte death in the 7-9 week window of development, which persisted to 10 months of age, at which time the CM-EGFR KO mice had progressively worsened cardiac function, dilation and cardiomyocyte loss. To investigate the impact of cardiomyocyte-specific EGFR deletion on the response to pathologic stress, we challenged 12-14 week old WT and CM-EGFR KO mice with chronic isoproterenol infusion. Notably, while chronic isoproterenol treatment diminished cardiac function and induced hypertrophic remodeling in WT mouse hearts, CM-EGFR-KO mouse hearts displayed progressively improved contractility and ablated hypertrophy over time, suggesting that EGFR differentially regulates cardiac function and remodeling processes during physiological versus pathological development.

Abstract P3-12-11: Disparities in adjuvant hormone adherence in breast cancer patients within a universal healthcare model

Background: Patient adherence to adjuvant hormonal therapy for breast cancer (BC) is correlated with improved survival. Recent publications have demonstrated ethnic disparities in adjuvant hormone adherence (AHA) for privatized healthcare models.

Objective: To identify disparities in AHA for BC patients within a universal healthcare system in Alberta, Canada.

Methods: Patients diagnosed from 2007-2014 with stage I-III, ER+/HER2- BC receiving adjuvant FECD or DC chemotherapy and at least one month of adjuvant hormonal therapy in Alberta, Canada were retrospectively assessed. Hormone monotherapy (tamoxifen, AI), switch strategies (tam to AI), and treatment duration were collected. Compliance was assessed with central pharmacy data. Patient ethnicity was identified using patient first/last and parental last name via Onolytics® ethnographic software. Ethnicity was further verified using a centrally collected place of birth. Age, AJCC stage, psychiatric diagnoses (mood, bipolar), and comorbidity were collected. Log rank and Chi squared were used to assess difference between adjuvant hormonal therapy for variables at 1, 2, and 5 years. Log rank p-values at 2 years are reported.

Results: A total of 2,399 ER+ patients were included for analysis. AHA was non-significant for ethnicity (p=0.797), comorbidity (p=0.623), psychiatric disorders (p=0.145), or elderly cohorts (p= 0.814). AHA by stage was significant with stage III > II > I (p=0.004) having the highest compliance rates. AHA was highest for planned hormonal switch strategies (p=0.004) compared to monotherapy.

Hormone Adherence RatesCharacteristicsNo. of Patients% AdherenceEthnicity  Caucasian211891.6Asian15293.4Middle Eastern/African9593.7Hispanic2491.7Age  <65207791.8>6534192.1Comorbidity  096191.21-3134392.2>311493Psychiatric Dx  Yes31189.7No210792.1Stage  I45388.3II151292.1III45394.5Hormone Strategy  Monotherapy173190.9Switch68794.2

Conclusion: AHA is not dependent on ethnicity, age, comorbidity, or psychiatric diagnosis in a universal healthcare model. Conversely, higher rates of AHA are seen with planned switch strategy compared to monotherapy, contradictory to the BIG I-98 trial. Patients with higher stage, and thus higher risk of BC recurrence have increased adherence compared to their low risk counterparts. Reinforcement of AHA for low/moderate risk BC patients, in addition to tamoxifen to AI switch strategies may improve overall adherence.

Citation Format: Veitch ZW, Khan OF, Tilley D, Kostaras X, King K, Lupichuk S, Tang P. Disparities in adjuvant hormone adherence in breast cancer patients within a universal healthcare model [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-12-11.

Abstract P5-20-12: Adjuvant DCH vs TCH for low-risk (node negative); and FECDH vs TCH for high-risk (node positive) HER2+ breast cancer – A retrospective provincial analysis

Background: Chemotherapy plus trastuzumab for early HER2+ breast cancer (BC) is associated with improved survival. Optimal regimens for low-risk (node negative) and high-risk (node positive) HER2+ breast cancers are unknown and choice of regimen varies in real-world clinical practice.

Objective: (1) For low-risk breast cancer, to compare DCH (4 cycles) and TCH (6 cycles) in terms of disease free (DFS) and overall survival (OS). (2) For high-risk breast cancer, to compare FECDH (6 cycles) and TCH (6 cycles) in terms of DFS and OS.

Methods: All women diagnosed from 2007-2014 with stage I-III, hormone receptor (HR) +/-, HER2+ BC receiving adjuvant chemotherapy plus trastuzumab (n=986) in Alberta, Canada were included. Patients with low-risk (node negative) disease were stratified into DCH (n=104) or TCH (n=360) cohorts for DFS/OS comparison (Kaplan-Meier). Patients with high-risk (node positive) disease were stratified into FECDH (n=145) or TCH (n=314) cohorts. Subgroup analysis of the high-risk cohorts by HR+/HER2+ and HR-/HER2+ for FECDH vs TCH were performed. Chi-square was used to evaluate for difference between cohort variables.

Low- Risk Cohort DCH TCH  n (104)%n (360)%Age (mean)55.3 53.0 Hormone Status    ER+ or PR+8682.727676.7ER and PR-1817.38423.3Grade    121.951.423230.88523.637067.327075.0Surgery    lumpectomy525010830.5mastectomy525024669.5

High-Risk Cohort FECDH TCH  n (145)%n (314)%Age (mean)50.2 53.6 Hormone Status    ER+ or PR+11579.323875.8ER and PR-3020.77624.2Grade    10051.6229206119.631168014678.8Surgery    lumpectomy3927.19831.2mastectomy10572.921668.8Node Status    N18357.219461.8N24128.37323.2N32114.54715

Results: Median follow-up was 58.1 months in the low-risk cohort and 63.1 months in the high-risk cohort. In the low-risk group, patients receiving TCH had more mastectomy (69.5%) than lumpectomy (30.5%; p<0.001) compared to those receiving DCH (50%; 50%). No significant difference was seen in DFS (p=0.153) or OS (p=0.409) for patients in the DCH (92.3%; 95.2%) vs TCH (95.2%; 96.9%) cohorts. In the high-risk group, no significant difference was seen in DFS (p=0.226) or OS (p=0.164) for FECDH (92.4; 95.2%) or TCH (88.5%; 91.4%) respectively. In subgroup analysis of high-risk HR+/HER2+ BC, patients receiving FECDH demonstrated superior OS (98.3%; p=0.014) and a trend towards superior DFS (94.8%; p=0.069) relative to TCH patients (OS = 91.6%; DFS= 88.7%). Conversely, analysis of high-risk HR-/HER2+ BC, patients demonstrated higher DFS and OS for TCH (88.2%; 90.8%) relative to FECDH (83.3%; 83.3%); although this was non-significant (p=0.516; p=0.298) and likely underpowered. Nodal status was balanced between all groups (p=0.602).

Conclusion: In low-risk HER2+ BC, 4 cycles of DCH chemotherapy has high survival with similar outcomes to 6 cycles of TCH. In high-risk HER2+ BC, FECDH has comparable outcomes to TCH consistent with BCIRG-006. This study suggests that women with HR+/HER2+ breast cancer have improved OS with anthracycline containing regimens, such as FECDH. Although non-significant, patients with HR-/HER2+ BC may have some improvement in DFS and OS with TCH, a carboplatin containing regimen.

Citation Format: Veitch ZW, Khan OF, Tilley D, Kostaras X, Tang PA, King K, Lupichuk S. Adjuvant DCH vs TCH for low-risk (node negative); and FECDH vs TCH for high-risk (node positive) HER2+ breast cancer – A retrospective provincial analysis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-20-12.

Interleukin-10 Inhibits Bone Marrow Fibroblast Progenitor Cell-Mediated Cardiac Fibrosis in Pressure-Overloaded Myocardium

BACKGROUND

Activated fibroblasts (myofibroblasts) play a critical role in cardiac fibrosis; however, their origin in the diseased heart remains unclear, warranting further investigation. Recent studies suggest the contribution of bone marrow fibroblast progenitor cells (BM-FPCs) in pressure overload-induced cardiac fibrosis. We have previously shown that interleukin-10 (IL10) suppresses pressure overload-induced cardiac fibrosis; however, the role of IL10 in inhibition of BM-FPC-mediated cardiac fibrosis is not known. We hypothesized that IL10 inhibits pressure overload-induced homing of BM-FPCs to the heart and their transdifferentiation to myofibroblasts and thus attenuates cardiac fibrosis.

METHODS

Pressure overload was induced in wild-type (WT) and IL10 knockout (IL10KO) mice by transverse aortic constriction. To determine the bone marrow origin, chimeric mice were created with enhanced green fluorescent protein WT mice marrow to the IL10KO mice. For mechanistic studies, FPCs were isolated from mouse bone marrow.

RESULTS

Pressure overload enhanced BM-FPC mobilization and homing in IL10KO mice compared with WT mice. Furthermore, WT bone marrow (from enhanced green fluorescent protein mice) transplantation in bone marrow-depleted IL10KO mice (IL10KO chimeric mice) reduced transverse aortic constriction-induced BM-FPC mobilization compared with IL10KO mice. Green fluorescent protein costaining with α-smooth muscle actin or collagen 1α in left ventricular tissue sections of IL10KO chimeric mice suggests that myofibroblasts were derived from bone marrow after transverse aortic constriction. Finally, WT bone marrow transplantation in IL10KO mice inhibited transverse aortic constriction-induced cardiac fibrosis and improved heart function. At the molecular level, IL10 treatment significantly inhibited transforming growth factor-β-induced transdifferentiation and fibrotic signaling in WT BM-FPCs in vitro. Furthermore, fibrosis-associated microRNA (miRNA) expression was highly upregulated in IL10KO-FPCs compared with WT-FPCs. Polymerase chain reaction-based selective miRNA analysis revealed that transforming growth factor-β-induced enhanced expression of fibrosis-associated miRNAs (miRNA-21, -145, and -208) was significantly inhibited by IL10. Restoration of miRNA-21 levels suppressed the IL10 effects on transforming growth factor-β-induced fibrotic signaling in BM-FPCs.

CONCLUSIONS

Our findings suggest that IL10 inhibits BM-FPC homing and transdifferentiation to myofibroblasts in pressure-overloaded myocardium. Mechanistically, we show for the first time that IL10 suppresses Smad-miRNA-21-mediated activation of BM-FPCs and thus modulates cardiac fibrosis.

Real-world adjuvant TAC or FEC-D for HER2-negative node-positive breast cancer in women less than 50 years of age

PURPOSE

We compared the efficacy, toxicity, and use of granulocyte colony-stimulating factor (g-csf) with tac (docetaxel-doxorubicin-cyclophosphamide) and fec-d (5-fluorouracil-epirubicin-cyclophosphamide followed by docetaxel) in women less than 50 years of age.

METHODS

The study included all women more than 18 years but less than 50 years of age with her2-negative, node-positive, stage ii or iii breast cancer diagnosed in Alberta between 2008 and 2012 who received tac (n = 198) or fec-d (n = 274).

RESULTS

The patient groups were well-balanced, except that radiotherapy use was higher in the tac group (91.9% vs. 79.9%, p < 0.001). At a median follow-up of 49.6 months, disease-free survival was 91.4% for tac and 92.0% for fec-d (p = 0.76). Overall survival (os) was 96% with tac and 95.3% with fec-d (p = 0.86).The incidences of grades 3 and 4 toxicities were similar in the two groups (all p > 0.05). Overall, febrile neutropenia (fn) was reported in 11.6% of tac patients and 15.7% of fec-d patients (p = 0.26). However, use of g-csf was higher in the tac group than in the fec-d group (96.4% vs. 71.5%, p < 0.001). Hospitalization for fn was required in 10.5% of tac patients and 13.0% of fec-d patients (p = 0.41). In g-csf-supported and -unsupported patients receiving tac, fn occurred at rates of 11.1% and 33.3% respectively (p = 0.08); in patients receiving the fec portion of fec-d, those proportions were 2.9% and 8.1% respectively (p = 0.24); and in patients receiving docetaxel after fec, the proportions were 4.1% and 17.6% respectively (p < 0.001).

CONCLUSIONS

In women less than 50 years of age receiving adjuvant tac or fec-d, we observed no differences in efficacy or other nonhematologic toxicities. Based on the timing and rates of fn, use of prophylactic g-csf should be routine for the docetaxel-containing portion of treatment; however, prophylactic g-csf could potentially be avoided during the fec portion of fec-d treatment.

Enactments in emotionally focused couple therapy: shaping moments of contact and change

Emotionally focused couple therapy (EFT) uses enactments to shape responsive attachment-significant contact and to change couple interaction. In this article, we show how EFT enactments differ from enactments in other therapy approaches, present a theory of EFT enactments, a model for creating EFT enactments, and an extended case example of an EFT enactment.

Invasive Streptococcus pneumoniae trigger platelet activation via Toll-like receptor 2

BACKGROUND

Sepsis is the most common manifestation of invasive pneumococcal disease and is characterized by a severe systemic inflammatory state that leads to circulatory compromise or end organ malperfusion or dysfunction. Patients suffering from sepsis often display low platelet counts characterized by thrombocytopenia as a result of platelet activation.

OBJECTIVE

To investigate the mechanism through which platelets become activated in sepsis upon binding to Streptococcus pneumoniae.

PATIENTS AND METHODS

We determined S. pneumoniae inducible platelet reactivity using light transmission aggregometry. Dense granule secretion was measured by luminometry using a luciferin/luciferase assay.

RESULTS

Streptococcus pneumoniae induced platelet aggregation in a strain-dependent manner. Induction of aggregation was not attributable to capsule serotype, as unencapsulated strains also induced platelet aggregation. Platelet aggregation was not associated with pneumolysin toxin, as a pneumolysin-deficient mutant of S. pneumoniae induced aggregation equally as well as the parent strain. Platelet aggregation also occurred in the absence of plasma proteins or antibody, and was GPIIbIIIa dependent but aspirin independent. Toll-like receptor 2 (TLR2) is present on platelets and acts as a receptor for gram-positive bacterial lipoteichoic acid and peptidoglycan. Inhibition of TLR2 but not TLR4 (also present on platelets) completely abolished platelet aggregation. S. pneumoniae-induced platelet aggregation resulted in activation of the PI3kinase/RAP1 pathway, leading to integrin GPIIbIIIa activation and dense granule release.

CONCLUSIONS

Our results demonstrate a novel interaction between S. pneumoniae and TLR2, which results in platelet activation that is likely to contribute to the thrombotic complications of sepsis.

Prevalence of community-associated methicillin-resistant Staphylococcus aureus colonization in men who have sex with men

Summary

Outbreaks of skin and soft tissue infections mediated by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) are being reported with increasing frequency among men who have sex with men (MSM). However, the potential role of asymptomatic colonization with this organism in perpetuating these infections is unclear. The purpose of this cross-sectional study was to determine the prevalence of colonization with CA-MRSA among a cohort of 500 MSM recruited from two inner city clinics in Toronto, Canada. Following the provision of informed consent, subjects completed a questionnaire capturing demographic and clinical variables, which may be associated with MRSA colonization. A nasal swab for MRSA was collected from each subject, and instructions were provided regarding the self-collection of a rectal swab. Cultured MRSA underwent pulsed-field gel electrophoresis and virulence testing for Panton-Valentine leukocidin gene expression. The prevalence of CA-MRSA colonization was 1.6% (95% CI: 0.5–2.6%).

Risk factors for grade 3-4 liver enzyme elevation in HIV and hepatitis C coinfected patients on combination antiretroviral therapy

Although coinfection with hepatitis C (HCV) is an established risk factor for hepatotoxicity in HIV-positive patients receiving combination antiretroviral therapy (cART), specific variables that may be predictive of severe hepatotoxicity among co-infected patients receiving cART remain poorly defined. A retrospective cohort study of HIV/HCV coinfected adults from two HIV treatment centers covering the period between December 1998 and December 2003 was conducted to address this question. The primary endpoint of the study was the occurrence of grade 3 or 4 elevation of serum alanine aminotransferase (ALT) during follow-up and the primary predictors of interest were specific antiretrovirals. One hundred five coinfected patients receiving cART for a median of 70 months (interquartile range [IQR], 37, 83) were included in the analysis. Twenty-three (22%) patients developed a grade 3 or 4 increase in serum ALT at least once in follow-up. In univariate analysis, current receipt of lopinavir/ritonavir (LPV/r) (odds ratio [OR] 3.09, 95% confidence interval [CI] 1.14-8.34, p = 0.03), baseline ALT (OR 1.01, 95% CI 1.00-1.02, p = 0.004), and current use of boosting ritonavir (OR 2.84, 95% CI 1.16-7.00, p = 0.02) were significantly associated with a grade 3 or 4 increase in serum ALT, although most patients receiving boosting ritonavir were on lopinavir/ritonavir based regimens. Patients receiving LPV/r had been previously exposed to significantly more antiretrovirals (p < 0.0001), protease inhibitors (p < 0.0001), and nucleoside analogues (p = 0.0009) compared to the rest of the cohort. Further research to better clarify risk factors for hepatotoxicity in coinfected patients is warranted given the challenges in treating this population.

Fetal hepatosplenomegaly associated with transient myeloproliferative disorder in trisomy 21

The in utero diagnosis of fetal myeloproliferative disease was made by cordocentesis following the ultrasound appearance of fetal hepatosplenomegaly and mild hydrops. The 2 fetuses reported both had leukocyte counts greater than 75,000/mm3 with a predominance of blast forms. In both cases the karyotype revealed trisomy 21.

Differences in reasons for smoking between younger and older smokers

The reasons why older people smoke have not been examined in the literature. This paper attempted to examine the differences in motivation and maintenance factors of elderly and young smokers using the Horn-Waingrow Why do you smoke questionnaire. One hundred and thirteen clinical patients and 112 non-patient controls were used in this study. The clinical group was divided into an elderly group (n = 58) and a younger group (n = 55). The results of a discriminant analysis showed that patients significantly differed from non-patients on 'automatic habit and stimulation', and 'crutch/tension reduction' factors. Elderly patients were found to be significantly differentiated from both younger patients and the control group on the 'pleasurable relaxation' factor. These findings offer support for the US Surgeon Generals' report that elderly smokers do have different motivating factors for their smoking behaviours from younger smokers.

Real time observations of polylysine, dextran and polyethylene glycol induced mutual adhesion of erythrocytes held in suspension in an ultrasonic standing wave field

A technique which enables cells to be observed in suspension for times of the order of minutes (employing acoustic radiation forces in a 1 MHz ultrasonic standing wave field) is described. Video recordings of the mutual adhesion of human erythrocytes in suspension have been analysed. Concave-ended cell doublets and linear rouleaux developed in 0.5-1.5% w/v Dextran T500 by a gradual (2.5-17 s) increase in the area of cell contact over the cell cross-section. The concave-ended rouleaux form was not seen in polylysine or in polyethylene glycol. In 5-7% dextran and in 20 micrograms/ml polylysine mutual adhesion was a two stage process. Cells first form a strong local contact which persists (without apparently growing in area) for a number of seconds following which the cell surfaces move suddenly to form a spherical doublet. The average initial contact time and engulfment time for cells in 7% Dextran T500 are 18 and 2.7s, respectively. The corresponding values for cells in 20 micrograms/ml, 14 kDa, polylysine are 2.7 and 0.3s. There was no initial contact delay during spherical doublet formation in 1 mg/ml polylysine. Electron microscopy showed that the intercellular seam for spherical doublets formed with all three agglutinating molecules was bent in a wavy lambda approximately equal to 4 micron) profile. The thickness of the intercellular space varied in a spatially periodic way (lambda approximately equal to 0.8 microns) for cells in polylysine. Examples of periodic intercellular spaces were seen by light microscopy in polyethylene glycol induced clumps. The role of interfacial instability in the adhesion processes is discussed.

Failure of oral tolerance in (NZB X NZW)F1 mice is antigen specific and appears to parallel antibody patterns in human systemic lupus erythematosus (SLE)

Primary oral antigen exposure normally induces mucosal immunity and an active suppression of the systemic immune response. Patients with systemic lupus erythematosus (SLE) have increased antibodies to bovine gamma-globulin (BGG), which suggested a possible failure of oral tolerance in SLE. We examined this possibility in murine lupus. NZB/W females were fed BGG or saline and were subsequently immunized ip. Primary and secondary responses were assessed. At 1 month of age the mice tolerized normally in response to feeding with BGG but, at 4 months of age, not only did they not tolerize, the mice fed BGG had a 5- to 7-fold higher response to parenteral immunization than did the saline-fed mice. Control strain mice tolerized normally at both ages (a 5- to 10-fold lower response). Conversely, when fed ovalbumin, NZB/W females tolerized normally at both 1 and 4 months of age, and patients with SLE had normal levels of antibody to this antigen. However, we also found increased levels of antibodies to bovine casein in SLE patients, and found that NZB/W mice failed to orally tolerize with this antigen at either 1 or 4 months of age. Thus, the failure of oral tolerance in the NZB/W mice appears to be antigen specific and age dependent and, at least with respect to these three antigens, appears to parallel the antibody patterns seen in human SLE.

Interfacial instability and the agglutination of erythrocytes by polylysine

Human erythrocytes have been exposed to polylysine of molecular weight range 4 to 220 kDa and concentration range 0.5 to 2,000 micrograms/ml at 37 degrees C. Threshold concentrations for cell agglutination by the polycation have been determined for the samples of different molecular weight. Light and electron micrographs show that, in the erythrocyte agglutinates, cell-cell contact is generally made only at discrete, spatially periodic, regions which are distributed over a significant part of the cell surface. The average spacing between contact regions is 0.83 micron. The cell membrane has a wavy profile between contact regions. Agglutination occurs only in cell samples whose electrophoretic mobility is significantly altered by polylysine and, in agreement with a previous report, occurs even when the electrophoretic mobility reaches high positive values. The electrophoretic mobility data implies that agglutination requires some protrusion of polylysine from the cell glycocalyx. We discuss how a resulting net attractive intercellular force could act to destabilize the aqueous layer between two cells, allowing surface wave growth which results in spatially periodic contact regions. Examples of situations where cell and membrane contact might by explained by the general concept of interfacial instability are discussed.