Attitudes toward the American Cancer Society's 2020 cervical cancer screening guidelines: A qualitative study of a national sample of US clinicians

BACKGROUND

The 2020 American Cancer Society (ACS) guidelines are the most recent national guidelines for cervical cancer screening. These guidelines propose two major changes from current practice: initiating screening at age 25 years and using primary human papillomavirus (HPV) testing. Adoption of guidelines often occurs slowly, and therefore understanding clinician attitudes is important to facilitate practice change.

METHODS

Interviews with a national sample of clinicians who perform cervical cancer screening in a variety of settings explored attitudes toward the two major changes from the 2020 ACS cervical cancer screening guidelines. Clinicians participated in 30- to 60-min interviews exploring their attitudes toward various aspects of cervical cancer screening. Qualitative analysis was performed.

RESULTS

Seventy clinicians participated from across the United States. Few respondents were initiating screening at age 25 years, and none were using primary HPV testing. However, over half would be willing to adopt these practices if supported by scientific evidence and recommended by professional medical organizations. Barriers to adoption included the lack of endorsement by professional societies, lack of laboratory availability and insurance coverage, limited autonomy within large health care systems, and concerns related to missed disease.

CONCLUSIONS

Few clinicians have adopted screening initiation or primary HPV testing, as recommended by the 2020 ACS guidelines, but over half were open to adopting these changes. Implementation may be facilitated via professional organization endorsement, clinician education, and laboratory, health care system, and insurance support.

PLAIN LANGUAGE SUMMARY

In 2020, the American Cancer Society (ACS) released updated guidelines for cervical cancer screening. The main changes to current practices were to initiate screening at age 25 years instead of age 21 years and to screen using primary human papillomavirus (HPV) testing rather than cytology alone or in combination with HPV testing. We performed in-depth interviews with 70 obstetrics and gynecology, family medicine, and internal medicine physicians and advanced practice providers about their attitudes toward these guidelines. Few clinicians are following the 2020 ACS guidelines, but over half were open to changing practice if the changes were supported by evidence and recommended by professional medical organizations. Barriers to adoption included the lack of endorsement by professional medical organizations, logistical issues, and concerns about missed disease.

Factors Associated With Guideline-concordant and Excessive Cervical Cancer Screening: A Mixed Methods Study

INTRODUCTION

National guidelines recommend cervical cancer screening with Papanicolaou (Pap) testing at 3-year intervals or with human papillomavirus (HPV) testing alone or HPV/Pap cotesting at 5-year intervals for average-risk individuals aged 30-65 years.

METHODS

We explored factors associated with clinician-reported guideline-concordant screening, as well as facilitators and barriers to appropriate cervical cancer screening.

RESULTS

A national sample of clinicians (N = 1,251) completed surveys; a subset (n = 55) completed interviews. Most (94%) screened average-risk patients aged 30-65 years with cotesting. Nearly all clinicians who were categorized as nonadherent to national guidelines were overscreening (98%). Guideline concordant screening was reported by 47% and 82% of those using cotesting and HPV testing, respectively (5-year intervals), and by 62% of those using Pap testing only (3-year intervals). Concordant screening was reported more often by clinicians who were aged <40 years, non-Hispanic, and practicing in the West or Midwest, and less often by obstetrician-gynecologists and private practice physicians. Concordant screening was facilitated by beliefs that updated guidelines were evidence-based and reduced harms, health care system dissemination of guidelines, and electronic medical record prompts. Barriers to concordant screening included using outdated guidelines, relying on personal judgment, concern about missing cancers, inappropriate patient risk assessment, and lack of support for guideline adoption through health care systems or electronic medical records.

CONCLUSIONS

Most clinicians screened with Pap/HPV cotesting and approximately one-half endorsed a 5-year screening interval. Clinician knowledge gaps include understanding the evidence underlying 5-year intervals and appropriate risk assessment to determine which patients should be screened more frequently. Education and tracking systems can promote guideline-concordant screening.

HPV vaccine recommendations by age: A survey of providers in federally qualified health centers

Clinician recommendation remains a critical factor in improving HPV vaccine uptake. Clinicians practicing in federally qualified health centers were surveyed between October 2021 and July 2022. Clinicians were asked how they recommended HPV vaccination for patients aged 9-10, 11-12, 13-18, 19-26, and 27-45 y (strongly recommend, offer but do not recommend strongly, discuss only if the patient initiates the conversation, or recommend against). Descriptive statistics were assessed, and exact binomial logistic regression analyses were utilized to examine factors associated with HPV vaccination recommendation in 9-10-y-old patients. Respondents (n = 148) were primarily female (85%), between the ages of 30-39 (38%), white, non-Hispanic (62%), advanced practice providers (55%), family medicine specialty (70%), and practicing in the Northeast (63%). Strong recommendations for HPV vaccination varied by age: 65% strongly recommended for ages 9-10, 94% for ages 11-12, 96% for ages 13-18, 82% for age 19-26, and 26% for ages 27-45 y. Compared to Women's Health/OBGYN specialty, family medicine clinicians were less likely to recommend HPV vaccination at ages 9-10 (p = .03). Approximately two-thirds of clinicians practicing in federally qualified health centers or safety net settings strongly recommend HPV vaccine series initiation at ages 9-10. Additional research is needed to improve recommendations in younger age groups.

Examining the perceived impact of the COVID-19 pandemic on cervical cancer screening practices among clinicians practicing in Federally Qualified Health Centers: A mixed methods study

Background

The COVID-19 pandemic led to reductions in cervical cancer screening and colposcopy. Therefore, in this mixed methods study we explored perceived pandemic-related practice changes to cervical cancer screenings in federally qualified health centers (FQHCs).

Methods

Between October 2021 and June 2022, we conducted a national web survey of clinicians (physicians and advanced practice providers) who performed cervical cancer screening in FQHCs in the United States during the post-acute phase of the COVID-19 pandemic, along with a sub-set of qualitative interviews via video conference, to examine perceived changes in cervical cancer screening practices during the pandemic.

Results

A total of 148 clinicians completed surveys; a subset (n=13) completed qualitative interviews. Most (86%) reported reduced cervical cancer screening early in the pandemic, and 28% reported continued reduction in services at the time of survey completion (October 2021- July 2022). Nearly half (45%) reported staff shortages impacting their ability to screen or track patients. Compared to clinicians in Obstetrics/Gynecology/Women's health, those in family medicine and other specialties more often reported reduced screening compared to pre-pandemic. Most (92%) felt that screening using HPV self-sampling would be very or somewhat helpful to address screening backlogs. Qualitative interviews highlighted the impacts of staff shortages and strategies for improvement.

Conclusions

Findings highlight that in late 2021 and early 2022, many clinicians in FQHCs reported reduced cervical cancer screening and of pandemic-related staffing shortages impacting screening and follow-up. If not addressed, reduced screenings among underserved populations could worsen cervical cancer disparities in the future.

Funding

This study was funded by the American Cancer Society, who had no role in the study's design, conduct, or reporting.

A cross-sectional survey examining clinician characteristics, practices, and attitudes associated with adoption of the 2019 American Society for Colposcopy and Cervical Pathology risk-based management consensus guidelines

BACKGROUND

The 2019 American Society for Colposcopy and Cervical Pathology (ASCCP) risk-based management consensus guidelines are the most recent national guidelines for the management of abnormal cervical cancer screening tests. These guidelines benefit patients by concentrating testing and treatment in those at highest cervical cancer risk. Adoption of guidelines often occurs slowly, with few studies examining the factors associated with guideline-adherent management of abnormal results.

METHODS

To elucidate the factors associated with the use of the 2019 ASCCP guidelines among clinicians who perform cervical cancer screening, physicians and advanced practice professionals who perform cervical cancer screening were cross-sectionally surveyed. Clinicians responded to screening vignettes with differing recommendations for management between the 2019 and prior management guidelines. Screening vignette 1 involved reduction of invasive testing on a low-risk patient; screening vignette 2 involved increased surveillance testing on a high-risk patient. Binomial logistic regression models determined the factors associated with the use of the 2019 guidelines.

RESULTS

A total of 1251 clinicians participated from across the United States. For screening vignettes 1 and 2, guideline-adherent responses were given by 28% and 36% of participants, respectively. Management recommendations differed by specialty and were incorrect in different situations: there was inappropriate invasive testing by obstetrics and gynecology physicians (vignette 1) and inappropriate discontinuation of screening by family and internal medicine physicians (vignette 2). Regardless of their chosen response, over half erroneously believed they were guideline adherent.

CONCLUSIONS

Many clinicians who believe they are following appropriate guidelines may not realize their management strategy is inconsistent with the 2019 guidelines. Education initiatives tailored to clinician specialty could address the understanding of current guidelines, encourage the use of updated guidelines, maximize patient benefits, and minimize harms.

PLAIN LANGUAGE SUMMARY

The 2019 American Society for Colposcopy and Cervical Pathology risk-based management consensus guidelines are the most recent national guidelines for abnormal cervical cancer screening test management. We surveyed over 1200 obstetrics and gynecology (OB/GYN), family medicine, and internal medicine physicians and advanced practice providers about their screening and abnormal results follow-up practices in relation to guidelines. Few clinicians are following the 2019 guidelines. Management recommendations differed by clinician specialty and were incorrect in different situations: there was inappropriate invasive testing by OB/GYN physicians and inappropriate screening discontinuation by family and internal medicine physicians. Education tailored by clinician specialty could address the understanding of current guidelines, encourage the use of updated guidelines, maximize patient benefits, and minimize harms.

Understanding Cancer Survivors' Educational Needs About Prescription Opioid Medications: Implications for Cancer Education and Health Literacy

Cancer survivors' perceptions of prescription opioid medication (POM) and the health communications they receive about POM's safety and effectiveness are embedded within the national discourse of the opioid epidemic. Using qualitative methods, this community-based study explored the health communication and the educational needs of diverse cancer survivors who received opioid agonist treatment to manage cancer pain. Our community-based sample consisted of 25 cancer survivors, 24 healthcare providers, and six community-level stakeholders. Over half of the cancer survivors interviewed were from underrepresented minority groups (52% African American and 12% Hispanic/Latino). The data were analyzed using applied thematic analysis techniques. The over-arching themes include the need to (1) provide clear, consistent, and comprehensive education and information about POM to ensure safe use; (2) discuss the risks, benefits, and proper use of POM in the treatment of cancer-related pain; (3) communicate realistic expectations and address common misconceptions about pain; and (4) address cancer survivor beliefs and concerns surrounding fear of addiction. Our findings highlight the need for effective cancer education and communication about opioid agonist treatment and POM in plain simple language that is easy to understand, relevant, and culturally appropriate. Recommendations for cancer education and suggestions for future research are discussed.

Perceptions of prescription opioid medication within the context of cancer survivorship and the opioid epidemic

PURPOSE

Prescription opioid medication can be of great benefit for cancer patients and survivors who suffer from cancer-related pain throughout their cancer care trajectory. However, the current opioid epidemic has influenced how such medications are perceived. The purpose of this study was to explore the perceptions of opioid use and misuse in cancer survivorship within the context of the opioid epidemic.

METHODS

pt?>A qualitative study using a semi-structured interview was conducted with a purposive sample of health care professionals (n = 24), community-level stakeholders (n = 6), and cancer survivors (n = 25) using applied thematic analysis techniques.

RESULTS

Crosscutting themes include (1) fear of addiction and living with poorly managed pain, (2) the importance of good patient/provider communication and the need for education around the use/handling/disposal of prescription opioid medication, (3) preference for nonopioid alternatives for pain management, (4) cancer survivors perceived to be low risk for developing opioid use disorder (include inconsistent screening), and (5) impact of policies aimed at curbing the opioid epidemic on cancer survivors.

CONCLUSION

This study illustrates the intersecting and sometimes conflicting assumptions surrounding the use of opioids analgesics in the management of cancer pain among survivors embedded within the national discourse of the opioid epidemic.

IMPLICATIONS FOR CANCER SURVIVORS

A system of integrated cancer care using psychosocial screening, opioid risk mitigation tools, opioid treatment agreements, and specialist expertise that cancer care providers can rely on to monitor POM use in conjunction with patient-centered communication to empower patients informed decision making in managing their cancer pain could address this critical gap in survivorship care.

Cubic crystals in an x-ray polarization-splitting geometry

Hexagonal and cubic crystals contain paired sets of internal planes that reflect the linearly polarized components of certain x rays into two separate, perpendicular directions. For the cubic crystals, two distinct crystal orientations provide the same polarization-splitting geometry. One of the orientations may have advantages for plasma spectroscopy by suppressing unwanted reflections. This paper demonstrates the two orientations with a germanium crystal and K characteristic lines from copper and zirconium.

Florida physicians' reported use of AFIX-based strategies for human papillomavirus vaccination

HPV vaccination rates in Florida are low. To increase rates, the CDC recommends clinics adhere to components of their evidence-based quality improvement program, AFIX (Assessment, Feedback, Incentives, and eXchange of information). We explored factors associated with engaging in HPV-specific AFIX-related activities. In 2016, we conducted a cross-sectional survey of a representative sample of 770 pediatric and family medicine physicians in Florida and assessed vaccination practices, clinic characteristics, and HPV-related knowledge. Data were analyzed in 2017. The primary outcome was whether physicians' clinics engaged in ≥1 AFIX activity. We stratified by physician specialty and developed multivariable models using a backward selection approach. Of the participants in the analytic sample (n = 340), 52% were male, 60% were White of any ethnicity, and 55% were non-Hispanic. Pediatricians and family medicine physicians differed on: years practicing medicine (p < 0.001), HPV-related knowledge (p < 0.001), and VFC provider status (p < 0.001), among others. Only 39% of physicians reported engaging in ≥1 AFIX activity. In the stratified multivariable model for pediatricians, AFIX activity was significantly associated with HPV-related knowledge (aOR = 1.33;95%CI = 1.08-1.63) and provider use of vaccine reminder prompts (aOR = 3.61;95%CI = 1.02-12.77). For family medicine physicians, HPV-related knowledge was significant (aOR = 1.57;95%CI = 1.20-2.05) as was majority race of patient population (non-Hispanic White vs. Other: aOR = 3.02;95%CI = 1.08-8.43), daily patient load (<20 vs. 20-24: aOR = 9.05;95%CI = 2.72-30.10), and vaccine administration to male patients (aOR = 2.98;95%CI = 1.11-8.02). Fewer than half of Florida pediatric and family medicine physicians engaged in any AFIX activities. Future interventions to increase AFIX engagement should focus on implementing and evaluating AFIX activities in groups identified as having low engagement in AFIX activities.

Characterization and calibration of a multilayer coated Wolter optic for an imager on the Z-machine at Sandia National Laboratories

The need for a time-resolved monochromatic x-ray imaging diagnostic at photon energies >15 keV has motivated the development of a Wolter optic to study x-ray sources on the Z-machine at Sandia National Laboratories. The work is performed in both the LLNL's x-ray calibration facility and SNL's micro-focus x-ray lab. Characterizations and calibrations include alignment, measurement of throughput within the field of view (FOV), the point-spread function within the FOV both in and out of focus, and bandpass in the FOV. These results are compared with ray tracing models, showing reasonable agreement.

The involvement of phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and MYPT1 isoform expression in NO/cGMP mediated differential vasoregulation of cerebral arteries compared to systemic arteries

AIM

Constitutive release of NO blunts intrinsic and stimulated contractile activity in cerebral arteries (CA). Here, we explored whether phosphorylation and expression levels of the PKG-sensitive, leucine zipper positive (LZ⁺ ) splice variants of the regulatory subunit of myosin phosphatase (MYPT1) are involved and whether its expression is associated with higher cGMP sensitivity.

METHODS

Vascular contractility was investigated by wire myography. Phosphorylation of MYPT1 was determined by Western blotting.

RESULTS

Constitutive phosphorylation of MYPT1-T696 and T853 was lower and that of S695 and S668 was higher in cerebral arteries from the circulus arteriosus (CA-w) than in femoral arteries (FA), while total MYPT1 expression was not different. In CA-w but not in FA, L-NAME lowered phosphorylation of S695/S668 and increased phosphorylation of T696/T853 and of MLC₂₀ -S19, plus basal tone. The increase in basal tone was attenuated in CA-w and basilar arteries (BA) from heterozygous MYPT1-T696A/+ mice. Compared to FA, expression of the LZ⁺ -isoform was ~2-fold higher in CA-w coincident with a higher sensitivity to DEA-NONOate, cinaciguat and Y27632 in BA and 8-Br-cGMP (1 μmol/L) in pre-constricted (pCa 6.1) α-toxin permeabilized CAs. In contrast, 6-Bnz-cAMP (10 μmol/L) relaxed BA and FA similarly by ~80%.

CONCLUSION

Our results indicate that (i) regulation of the intrinsic contractile activity in CA involves phosphorylation of MYPT1 at T696 and S695/S668, (ii) the higher NO/cGMP/PKG sensitivity of CAs can be ascribed to the higher expression level of the LZ⁺ -MYPT1 isoform and (iii) relaxation by cAMP/PKA pathway is less dependent on the expression level of the LZ⁺ splice variants of MYPT1.

An environmental scan to examine stakeholder perspectives on human papillomavirus vaccination: A mixed methods study

PURPOSE

Human papillomavirus (HPV) vaccine series completion rates among females and males remain low in Florida (46.4% and 34.5%, respectively). Multiple stakeholders influence vaccination uptake, including health care providers (HCPs), public health professionals (PHPs), and members of professional organizations. We examined stakeholder efforts related to increasing vaccine uptake and education among parents/adolescents and HCPs.

METHODS

We conducted an environmental scan of stakeholder efforts and identified stakeholders using our professional networks and a snowball sampling approach. Stakeholders (n = 46) completed a survey about involvement in and barriers to vaccination promotion efforts. A subset (n = 12) of stakeholders participated in follow-up interviews further exploring vaccination efforts and barriers. Survey data were analyzed using descriptive statistics. Interview data were analyzed using deductive analysis and coded using constructs from the PRECEDE-PROCEED model.

RESULTS

The majority of our survey sample was PHPs (50.0%) and HCPs (32.6%). Stakeholder efforts were focused on adolescent/parent/HCP education including providing: educational materials for HCPs (55.8%) and adolescents/parents (59.6%), one-on-one consultations for adolescents/parents (55.3%), and HCP education (54.7%). Lack of knowledge/understanding and education/information were barriers reported across almost all groups/areas. Office staff/HCP education and distribution of patient education materials were efforts described as important during qualitative interviews. Stakeholders also noted HCP discomfort when recommending HPV vaccine, parental perceptions that the vaccine is unnecessary, and a lack of education/understanding among parents and HCPs.

CONCLUSIONS

Results suggest the need for parent/adolescent education, specifically targeting key areas we identified: importance and benefits of HPV vaccine, and education and skill building in vaccine communication for HCPs.

Human Papillomavirus Vaccination Training Experience Among Family Medicine Residents and Faculty

BACKGROUND AND OBJECTIVES

Residency training is a pivotal time to establish skills for career-long practices, particularly for challenging skills such as human papillomavirus (HPV) vaccine recommendation. Training experience and preferences related to delivering HPV vaccine recommendations were examined for family medicine (FM) residents and faculty.

METHODS

Residents (n=28) and faculty (n=19) were identified through a national FM residency directory and recruited from training programs in Florida. Participants completed a phone interview assessing key aspects of HPV vaccine recommendation training. Interviews were audio recorded, transcribed verbatim, and analyzed using content analysis. A brief follow-up survey assessing training, practices, and demographics was emailed after the interview.

RESULTS

Residents' training experience with HPV vaccine recommendation varied from none to extensive, and was often self-directed. Variation in training was seen between and within programs. Faculty often noted HPV vaccination training was not standardized and residents lacked instruction about effective communication. Most programs relied on preceptors for training residents but training from preceptors varied widely and was often not standardized within the program.

CONCLUSIONS

This study identified a lack of consistent and standardized training for delivering HPV vaccine recommendations. A training curriculum that uses multiple modalities and reflects resident and faculty preferences is needed.

Physicians' current use and preferences for male HPV vaccine-related patient education materials

Understanding physician preferences for educational materials to support male HPV vaccination is critical to improving vaccine uptake. Pediatric (Peds) and Family Medicine (FM) physicians in Florida completed a survey from May-August 2014 assessing current use of male-specific HPV vaccination patient education materials, and preferences for materials to increase HPV vaccination uptake. Peds and FM responses were compared with chi-squared or nonparametric tests. Most participants were FM (53.2%), White (66.6%), non-Hispanic (74.1%), and provided male patients/parents with HPV educational materials (59.1%). More than half (55.5%) provided a CDC factsheet for parents. Peds were more likely to indicate they provide educational materials (p<0.0001) than FM. The preferred source was the CDC (77.8%). Peds preferred using a factsheet as the medium of information more often than FM (85.6% vs. 68.0%; p<0.0001). When asked about preferences for targeted materials, 74.8% of providers indicated they would prefer materials targeted towards patients, 63.2% preferred information targeted towards parents, and 20.7% indicated they prefer non-targeted materials. Future research should focus on the development and testing of new HPV vaccine-specific materials and communication strategies for Peds and FM physicians.

Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited)

The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (xop) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration data confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.

X-ray intensity and source size characterizations for the 25 kV upgraded Manson source at Sandia National Laboratories

At Sandia National Laboratories, the x-ray generator Manson source model 5 was upgraded from 10 to 25 kV. The purpose of the upgrade is to drive higher characteristics photon energies with higher throughput. In this work we present characterization studies for the source size and the x-ray intensity when varying the source voltage for a series of K-, L-, and M-shell lines emitted from Al, Y, and Au elements composing the anode. We used a 2-pinhole camera to measure the source size and an energy dispersive detector to monitor the spectral content and intensity of the x-ray source. As the voltage increases, the source size is significantly reduced and line intensity is increased for the three materials. We can take advantage of the smaller source size and higher source throughput to effectively calibrate the suite of Z Pulsed Power Facility crystal spectrometers.

Delayed therapy with a polymyxin B-dextran conjugate (PMX-622) improves survival in rabbits with Gram-negative peritonitis

Polymyxin B (PMB) is an amphipathic nephrotoxic antibiotic, which has been shown to neutralize the effects of endotoxin both in vitro and in vivo. PMB-D70 (PMX-622), a covalent conjugate of PMB with dextran 70 (D70), is less nephrotoxic than the parent compound. We sought to determine whether therapy with PMB-D70, in addition to conventional antimicrobial chemotherapy, could improve survival in a model of Gram-negative peritonitis. At T = 0 h, New Zealand white rabbits were implanted intraperitoneally with 10 ml of a suspension containing hemoglobin (40 μg/ml), mucin (150 μg/ml), and 1.0 ± 0.2 x 104 cfu/kg of viable Escherichia coli (O18:K1). Beginning at T = 4 h, the rabbits were treated with gentamicin (5 mg/kg every 12 h) for five doses or until death, and infused for 24 h or until death with either D70 or PMB-D70. Two pairs of groups were studied (doses indicate cumulative amounts infused over 24 h). The PMB-D70 (low dose) group received PMB-D70 (5 mg/kg of the PMB component) and the D70 (low dose) group received an equivalent dose of D70. The PMB-D70 (high dose) group received PMB-D70 (10 mg/kg of the PMB component) and the D70 (high dose) group received an equivalent dose of D70. Results for the two PMB-D70 groups, on the one hand, and the two D70 group, on the other hand, were statistically indistiguishable and, accordingly, were pooled for all analyses. Survival at 7 days was 11/25 (44%) for rabbits treated with PMB-D70 as compared to 2/23 (9%) for animals treated with D70 ( P = 0.007). We conclude that adjuvant treatment with PMB-D70 improves survival in a clinically relevant model of Gram-negative sepsis.

Spectroscopic modeling and characterization of a collisionally confined laser-ablated plasma plume

Plasma plumes produced by laser ablation are an established method for manufacturing the high quality stoichiometrically complex thin films used for a variety of optical, photoelectric, and superconducting applications. The state and reproducibility of the plasma close to the surface of the irradiated target plays a critical role in producing high quality thin films. Unfortunately, this dense plasma has historically eluded quantifiable characterization. The difficulty in modeling the plume formation arises in the accounting for the small amount of energy deposited into the target when physical properties of these exotic target materials are not known. In this work we obtain the high density state of the plasma plume through the use of an experimental spectroscopic technique and a custom spectroscopic model. In addition to obtaining detailed temperature and density profiles, issues regarding line broadening and opacity for spectroscopic characterization will be addressed for this unique environment.

X-ray absorption spectroscopy measurements of thin foil heating by Z-pinch radiation

Absorption spectroscopy measurements of the time-dependent heating of thin foils exposed to intense z-pinch radiation sources are presented. These measurements and their analysis provide valuable benchmarks for, and insights into, the radiative heating of matter by x-ray sources. Z-pinch radiation sources with peak powers of up to 160 TW radiatively heated thin plastic-tamped aluminum foils to temperatures approximately 60 eV. The foils were located in open slots at the boundary of z-pinch hohlraums surrounding the pinch. Time-resolved Kalpha satellite absorption spectroscopy was used to measure the evolution of the Al ionization distribution, using a geometry in which the pinch served as the backlighter. The time-dependent pinch radius and x-ray power were monitored using framing camera, x-ray diode array, and bolometer measurements. A three-dimensional view factor code, within which one-dimensional (1D) radiation-hydrodynamics calculations were performed for each surface element in the view factor grid, was used to compute the incident and reemitted radiation flux distribution throughout the hohlraum and across the foil surface. Simulated absorption spectra were then generated by postprocessing radiation-hydrodynamics results for the foil heating using a 1D collisional-radiative code. Our simulated results were found to be in good general agreement with experimental x-ray spectra, indicating that the spectral measurements are consistent with independent measurements of the pinch power. We also discuss the sensitivity of our results to the spectrum of the radiation field incident on the foil, and the role of nonlocal thermodynamic equilibrium atomic kinetics in affecting the spectra.

Combinatorial approaches to inhibitors of VLA-4: piperazine-peptoid-bisarylureas

A combinatorial approach towards identifying inhibitors of VALA-4 was investigated. A library of piperazine-peptoid-bisarylureas was assembled in solid phase and screening in the novel v-well assay enabled the identification of active compounds.

Optimization of the anti-(human CD3) immunotoxin DT389-scFv(UCHT1) N-terminal sequence to yield a homogeneous protein

The production and regulatory approval processes for biopharmaceuticals require detailed characterization of potential products. Therapeutic proteins should preferably be homogeneous, although limited, reproducible, heterogeneity may be tolerated. A diphtheria toxin-based anti-(human CD3) immunotoxin, DT389-scFv(UCHT1), was expressed in Escherichia coli and purified following refolding [DT389 corresponds to amino acids 1-389 of diphtheria toxin, scFv is single-chain variable-region antibody fragment and UCHT1is an anti-(human CD3) monoclonal antibody]. Biochemical characterization of this molecule by MS and N-terminal sequencing by Edman degradation revealed that the protein was heterogeneous at the N-terminus, containing species both with (60%) and without (40%) the initiator methionine residue. In an attempt to generate an N-terminally homogeneous molecule, a panel of seven N-terminal variants was designed, based on the published specificity of bacterial methionine aminopeptidase. Following bacterial expression, partial purification and separation on SDS/PAGE, these proteins were subjected to N-terminal sequencing by Edman degradation. Three of the mutants yielded a 100% homogeneous amino acid sequence. By contrast, the original DT389-scFv(UCHT1) protein and four variant proteins yielded two sequences with varying ratios corresponding to species with and without methionine. The N-terminal sequences of the three homogeneous clones were MLADD and MLDD, where the methionine was completely retained, and SADD, where the methionine was completely removed. One of the homogeneous mutants (SADD) was expressed, refolded and purified and found to be equipotent with the parent immunotoxin. Thus, using a rational mutagenesis approach, three N-terminally homogeneous variants of DT389-scFv(UCHT1) have been identified, at least one of which is functionally indistinguishable from the parent immunotoxin. This approach is generally applicable to biopharmaceutical production and immunotoxin development in particular.

Improved binding of a bivalent single-chain immunotoxin results in increased efficacy for in vivo T-cell depletion

Anti-CD3 immunotoxins exhibit considerable promise for the induction of transplantation tolerance in pre-clinical large animal models. Recently an anti-human anti-CD3epsilon single-chain immunotoxin based on truncated diphtheria toxin has been described that can be expressed in CHO cells that have been mutated to diphtheria toxin resistance. After the two toxin glycosylation sites were removed, the bioactivity of the expressed immunotoxin was nearly equal to that of the chemically conjugated immunotoxin. This immunotoxin, A-dmDT390-sFv, contains diphtheria toxin to residue 390 at the N-terminus followed by VL and VH domains of antibody UCHT1 linked by a (G(4)S)(3) spacer (sFv). Surprisingly, we now report that this immunotoxin is severely compromised in its binding affinity toward CD3(+) cells as compared with the intact parental UCHT1 antibody, the UCHT1 Fab fragment or the engineered UCHT1 sFv domain alone. Binding was increased 7-fold by adding an additional identical sFv domain to the immunotoxin generating a divalent construct, A-dmDT390-bisFv (G(4)S). In vitro potency increased 10-fold over the chemically conjugated immunotoxin, UCHT1-CRM9 and the monovalent A-dmDT390-sFv. The in vivo potency of the genetically engineered immunotoxins was assayed in the transgenic heterozygote mouse, tgepsilon 600, in which the T-cells express human CD3epsilon as well as murine CD3epsilon. T-cell depletion in the spleen and lymph node observed with the divalent construct was increased 9- and 34-fold, respectively, compared with the monovalent construct. The additional sFv domain appears partially to compensate for steric hindrance of immunotoxin binding due to the large N-terminal toxin domain.

Design and synthesis of potent and selective inhibitors of integrin VLA-4

The synthesis and identification of a novel series of inhibitors of integrin VLA-4 are described. Their in vitro activity and selectivity against closely related integrins are also presented.

Influence of relative binding affinity on efficacy in a panel of anti-CD3 scFv immunotoxins

The in vitro cell killing potency of an immunotoxin reflects the aggregate of several independent biochemical properties. These include antigen binding affinity; internalization rate, intracellular processing and intrinsic toxin domain potency. This study examines the influence of antigen binding affinity on potency in various immunotoxin fusion proteins where target antigen binding is mediated by single chain antibody variable region fragments (scFv). Firstly, the relationship between affinity and potency was examined in a panel of four scFv immunotoxins generated from different anti-CD3 monoclonal antibodies fused to the 38 kDa fragment of Pseudomonas aeruginosa exotoxin A (PE38). Of these four scFv-PE38 immunotoxins, the one derived from the anti-CD3 monoclonal antibody UCHT1 has highest cell killing potency. Analysis of these four scFv-PE38 immunotoxins indicated a correlation between antigen binding affinity and immunotoxin potency in the cell killing assay with the exception of the scFvPE38 immunotoxin derived from the antibody BC3. However this scFv appeared to suffer a greater drop in affinity ( approximately 100x), relative to the parent Mab than did the other three scFvs used in this study (2-10x). Secondly, the scFv(UCHT1)-PE38 immunotoxin was then compared with a further panel of scFv(UCHT1)-derived immunotoxins including a divalent PE38 version and both monovalent and divalent Corynebacterium diphtheriae toxin (DT389) fusion proteins. When the scFv-UCHT1 domain was amino-terminally positioned relative to the toxin, as in the scFv(UCHT1)-PE38, an approximately 10-fold higher antigen-binding affinity was observed than with the C-terminal fusion, used in the DT389-scFv(UCHT1) molecule. Despite this lower antigen-binding activity, the DT389-scFv immunotoxin had a 60-fold higher potency in the T-cell-killing assay. Thirdly, a divalent form of the DT389-scFv construct, containing tandem scFv domains, had a 10-fold higher binding activity, which was exactly reflected in a 10-fold increase in potency. Therefore, when comparing immunotoxins in which scFvs from different antibodies are fused to the same toxin domain (DT or PE) a broad correlation appears to exist between binding affinity and immunotoxin potency. However, no correlation between affinity and potency appears to exist when different toxin domains are combined with the same scFv antibody domain.

A high-capacity alkaline phosphatase reporter system for the rapid analysis of specificity and relative affinity of peptides from phage-display libraries

We describe a novel reporter enzyme cassette system which enables the analysis of large numbers of linear and cyclic peptides in terms of their binding to a specific target molecule. In this system, peptides selected for target binding from random peptide phage-display libraries are expressed as cloned fusion proteins with bacterial alkaline phosphatase. The binding specificity and relative affinity of each peptide-enzyme fusion protein is then evaluated in a target-specific ELISA. This strategy enables direct identification of the highest affinity peptides, specific for a given target, which can then be sequenced at the DNA level to derive their peptide sequences. This eliminates the need to sequence large numbers of clones to establish consensus sequences for binding peptides. This approach also eliminates the need for peptide synthesis or phage ELISA to determine relative binding affinities, which can be technically difficult. Identification of binding peptides based on specificity and relative affinity, rather than conforming to an amino acid consensus sequence, enables the rapid evaluation of hundreds of candidate peptides and identification of rare (non-consensus) binding peptides which may otherwise be missed.

A homogeneous fluorometric assay for measuring cell adhesion to immobilized ligand using V-well microtiter plates

We have developed a homogeneous high-capacity assay format for measuring integrin- and selectin-dependent cell binding to immobilized ligand using V-well microtiter plates. 2',7'-Bis(2-carboxyethyl)-5-(and-6)-carboxylfluorescence, acetoxymethylester-labeled cells are added to ligand-coated V-shaped microtiter wells. Bound cells are separated from free cells using centrifugal force to produce shear stress. Nonadherent cells accumulate in the nadir of the well and are measured using a fluorescence plate reader. Antibody or low-molecular-weight inhibitors of either the ligand or the cell surface receptor result in less cell binding, more cells in the pellet, and increased signal. The optimization and validation of the very late antigen-4/vascular cell adhesion molecule-1 assay is described in detail. We demonstrate that this assay can be rapidly adapted to measure other integrin- and selectin-mediated interactions. This assay format has several advantages over conventional assays. The centrifugal process is biologically relevant and eliminates the washing steps to remove nonadherent cells that can cause well-to-well and plate-to-plate variation. Because the assay is robust with a high signal-to-noise ratio and low variability, it is ideally suited for studying multiple parameters of cell adhesion and for high capacity screening.

A high-capacity quantitative mouse model of drug-mediated immunosuppression based on rejection of an allogeneic subcutaneous tumor

We describe a high-capacity in vivo assay to measure drug-mediated transplant immunosuppression using a mouse model of Sa1 tumor rejection. Sa1 grew poorly and was rejected by 14 days in immunocompetent allogeneic recipient mice. In nude (nu/nu) mice, Sa1 grew more rapidly and was not rejected, confirming the T cell dependence of this response. In immunocompetent animals, administration of immunosuppressive agents resulted in increased tumor growth relative to vehicle-treated animals. Treatment with immunosuppressive drugs such as cyclosporin A (CsA), 40-O-(2-hydroxyethyl)-rapamycin (SDZ RAD), or 2-amino-2-[2-(4-octylphenyl)ethyl]-1,2-propanediol hydrochloride (FTY720) produced dose-dependent inhibition of tumor rejection. By contrast, the drugs did not affect Sa1 tumor growth in nu/nu mice, which is consistent with their predicted indirect effect on tumor size by suppressing immunity, rather than by directly stimulating Sa1 growth. Drug potency, which is usually not described for immunosuppressive agents, was calculated from the linear relationship between drug dose and tumor volume. The potency of CsA was inversely related to the stringency of the histocompatibility barrier. Another advantage of this assay is that the endpoint is an objective size measurement over a short time period, compared with transplant models where the endpoint may not be reached for many weeks and may be more subjective. In addition, this model can measure the potency of combination drug treatments and compare new immunosuppressive drug regimens. For example, the administration of SDZ RAD or FTY720 with CsA resulted in a more than additive increase in potency, compared with the sum of the drugs as single agents.

Wavelength-dependent measurements of optical-fiber transit time, material dispersion, and attenuation

A new, to our knowledge, method for measuring the wavelength dependence of the transit time, material dispersion, and attenuation of an optical fiber is described. We inject light from a 4-ns rise-time pulsed broadband flash lamp into fibers of various lengths and record the transmitted signals with a time-resolved spectrograph. Segments of data spanning a range of approximately 3000 A are recorded from a single flash-lamp pulse. Comparison of data acquired with short and long fibers enables the determination of the transit time and the material dispersion as functions of wavelength dependence for the entire recorded spectrum simultaneously. The wavelength-dependent attenuation is also determined from the signal intensities. The method is demonstrated with experiments using a step-index 200-mum-diameter SiO(2) fiber. The results agree with the transit time determined from the bulk glass refractive index to within ?0.035% for the visible (4000-7200-A) spectrum and 0.12% for the UV (2650-4000-A) spectrum and with the attenuation specified by the fiber manufacturer to within ?10%.

Effect of a conjugate of polymyxin B-dextran 70 in horses with experimentally induced endotoxemia

OBJECTIVE

To determine the efficacy of polymyxin B-dextran 70 (PBD) for treatment of endotoxemic horses.

ANIMALS

15 horses during study 1 and 6 horses during study 2.

PROCEDURES

3 groups were used in study 1. Horses in groups 1 and 2 were given 30 ng of lipopolysaccharide (LPS)/kg of body weight, IV, over 60 minutes. Horses in group 3 were given saline (0.9% NaCl) solution. Beginning 15 minutes before LPS infusion and continuing for 75 minutes, horses in groups 1 and 3 were given PBD, IV. Horses in group 2 were given dextran 70. Blood samples were obtained for hemograms and determination of cytokine, lactate, and prostanoid concentrations. In study 2, horses were given ketoprofen (2.2 mg/kg) or saline solution 15 minutes before infusion of PBD. Fourteen days later, treatments were reversed, using a crossover design. Blood samples were obtained for measurement of thromboxane B2 (TXB2) concentration.

RESULTS

For study 1, prior treatment with PBD completely blocked endotoxin-induced changes for heart and respiratory rates, rectal temperature, WBC count, and plasma tumor necrosis factor, interleukin 6, TXB2, and prostaglandin F1 concentrations. There was transient tachypnea, sweating, and increased plasma TXB2 concentration in horses given PBD (with or without LPS). Prior treatment with ketoprofen eliminated all PBD-induced signs and prevented the increase in plasma TXB2 concentration.

CONCLUSIONS

Signs of endotoxemia were prevented in horses by treatment with PBD, although its use was associated with mild adverse effects.

CLINICAL RELEVANCE

When used in combination with a cyclooxygenase-inhibiting drug, PBD has potential for treatment of horses with endotoxemia.

Therapeutic efficacy of a polymyxin B-dextran 70 conjugate in experimental model of endotoxemia

Numerous studies have suggested that lipopolysaccharide (LPS), a major component of the cell wall of gram-negative bacteria, is responsible for the initiation of gram-negative septic shock. Previously, others have designed therapeutic regimens to target the biologically active lipid A region of LPS by either neutralization of the biological properties of LPS or enhancement of clearance of this molecule. One such compound capable of neutralizing lipid A is the antibiotic polymyxin B. However, the clinical utility of polymyxin B is limited by its toxicity. We therefore covalently conjugated this antibiotic to the high-molecular-weight polysaccharide dextran 70, resulting in reduced toxicity of polymyxin B but retention of its endotoxin-neutralizing ability. The studies described in this report were designed to test the in vivo efficacy of this compound in an experimental animal model of gram-negative septic shock. Mice were administered graded doses of Escherichia coli or Pseudomonas aeruginosa along with D-galactosamine and the antibiotic imipenem. We had previously determined that antibiotic chemotherapy provides significant protection against E. coli-mediated lethality with smaller doses of bacteria; however, the antibiotic does not provide protection against larger doses of bacteria, but it is effective at killing the bacterial inoculum in vivo. Administration of the polymyxin B-dextran 70 conjugate provided significant protection when given with an antibiotic but was not effective by itself. A requirement for a pretreatment period prior to E. coli challenge was shown to depend upon the bacterial challenge dose. In other studies using this D-galactosamine sensitization model, we demonstrated that the lipid A-specific conjugate had no effect on lethality caused by staphylococcus aureus or tumor necrosis factor alpha. The results of these studies indicate that this compound is effective in preventing lethal gram-negative septic shock in mice and may be useful as a potential therapeutic agent in humans as well.

Binding epitope of somatostatin defined by phage-displayed peptide libraries

We have developed a versatile phagemid system to display peptides on the surface of M13 bacteriophage at a copy number which approaches monovalency. In this system, a phagemid encodes a peptide fused to the amino-terminus of the second domain (dII) of the minor coat protein pIII under control of the inducible lac promoter. The fusion protein is displayed in combination with several copies of wild-type pIII on the surface of phage. Two diverse random octapeptide libraries, one linear and one which contained flanking cysteines capable of forming disulfide bridges, were were generated using an in vitro mutagenesis approach and affinity selected on an anti-somatostatin mAb. Peptides with high affinity for the mAb were enriched only from the cyclic library and the tetrapeptide, FWKT, was identified by consensus as the binding epitope. The selected peptides exhibited not only the primary amino acid sequence but also shared structural features with somatostatin. One peptide, CRFWKTWC, also exhibited nanomolar affinities for the five known somatostatin receptor subtypes. This system can easily be adapted to display individual peptides or a wide range of custom peptide libraries.

Primate antibodies to components of the human immune system

The feasibility to raise nonhuman primate antibodies against selected components of the human immune system was tested. The immunogens were whole cells (human T lymphocytes) or purified, recombinant human proteins (cytokines: TNF alpha or GM-CSF; soluble forms of cell surface antigens: sCD4 or sCD25). Significant immunizations, yielding functionally relevant antibodies, were readily achieved in rhesus monkeys, but, not surprisingly, may be less frequent in chimpanzees. The results suggest a general strategy for production of therapeutically useful MAB.

Isolation and characterization of a novel human monoclonal antibody that neutralizes tetanus toxin

A human monoclonal antibody, designated 53-2-4, has been isolated and characterized in terms of its ability to interact with clostridial neurotoxins. In enzyme-linked immunosorbent assay assays the antibody reacted with native tetanus toxin, tetanus toxoid and the C fragment obtained from the carboxyterminus of the toxin (AA 864-1314). The antibody did not react with the B fragment of tetanus toxin (AA 1-863) or with six serotypes of botulinum neurotoxin (A to F). Both culture supernatant from the clonal line producing the antibody as well as homogeneous protein obtained by affinity purification of the antibody neutralized tetanus toxin. When tested in vivo, the antibody provided complete production against a supralethal injection of toxin; when tested in vitro, the antibody produced at least 99% inactivation of a 1 x 10(-9) M solution of toxin. The exceptional neutralizing activity of the antibody was attributed to its high affinity for the toxin (4.2 x 10(-10) mol/liter). Animal experiments revealed a novel phenomenon that has been labeled delayed intoxication. At the appropriate ratio of antibody to antigen, the toxin was retained in the host in a latent form. After several days the biological activity of the toxin became apparent and there was onset of nervous system poisoning. Isolated tissue experiments showed that each antibody molecule is capable of associating with two antigen molecules. The antibody has greater neutralizing activity when mixed with free toxin than when mixed with toxin already bound to plasma membrane receptors.

Topographical and conformational epitopes of bovine papillomavirus type 1 defined by monoclonal antibodies

Monoclonal antibodies (MAbs) were generated against sodium dodecyl sulfate-disrupted bovine papillomavirus type 1 (BPV-1). When screened by enzyme-linked immunosorbent assay (ELISA) on intact and disrupted BPV-1, -2, and deer papillomavirus, three patterns of reactivity were defined: reactivity only with intact virus, with both intact and disrupted virus, and only with disrupted virus. On the basis of ELISA results, the topographical location and requirement for conformation for immunoreactivity of epitopes was defined as external conformational, external linear, and internal linear. Cross-reactivity of MAbs with other papillomavirus types was analyzed by immunofluorescence on warts from different species. Type-specific, BPV-1 and/or -2 cross-reactive, broadly cross-reactive, and genus-specific MAbs were identified. MAb reactivity with structural polypeptides of BPV-1 was analyzed by Western blot. MAbs reactive with epitopes defined as conformational by ELISA did not react in Western blot. All MAbs reactive in Western blot reacted with the major capsid protein (MCP) [55 kilodalton (kDa)], demonstrating that the MCP carries both type-specific and cross-reactive epitopes. Most MAbs reactive with the MCP were cross-reactive with structural polypeptides of 48 and 96 kDa, demonstrating the immunologic relatedness of these three polypeptides.

Functional interactions of human and murine lymphoid cells. I. Analysis of primary and secondary responses

In this study human T-cell responses against murine alloantigens were analyzed. The results show that optimal primary responses are obtained from peripheral blood mononuclear cells only when murine splenic adherent cells (SAC) were used as antigen. Further analysis revealed that human T cells were able to respond directly to murine cells without the need for antigen reprocessing; however, human interleukin 1 (IL-1) was required for optimal stimulation. In contrast, secondary proliferative responses to murine cellular antigens could be induced from primed T cells even in the absence of SAC and/or IL-1. These proliferative responses, and in addition, cytotoxic T-cell responses, were specific for the priming antigen. Long-term human T-cell lines specific for murine alloantigens were found to replace the need for murine T cells in antigen-specific murine B-cell responses to sheep red blood cells. The mechanism of help delivered by the human T cells appeared to be by the release of nonspecific helper-T-cell factors. The evidence presented for this is the inability of these cells to stimulate cells from mice that express the X chromosome B-cell defect xid.

T-cell replacing factor activity of recombinant-derived interleukin-2 requires gamma-interferon

In this study we show that recombinant-derived human interleukin-2 (rIL-2) has potent T-cell replacing activity in antigen-driven murine antibody responses of T-depleted spleen cells. This T-cell replacing factor (TRF) effect of rIL-2 is antigen specific. By the use of a variety of antibodies to gamma-interferon (IFN-gamma), including antibody from an interspecies hybridoma, we demonstrate that this TRF activity depends upon the production of IFN-gamma in the responding cell cultures, i.e., antibody to IFN-gamma blocks TRF activity. In addition, we show that the cell-to-cell allogeneic helper effect of T cells for antibody responses is similarly inhibited by antibodies to IFN-gamma. The inhibition of response produced by the antibodies is reversed by the addition of excess rIFN-gamma to the cultures. The results demonstrate that IFN-gamma is a necessary intermediate mediator for TRF activity mediated by IL-2 and also by T-cell-mediated help for B cells. Thus, even recombinant-derived lymphokines have complex secondary levels of action on responding cells. Antibodies to individual lymphokines are clearly a powerful resource to analyze the role of soluble factors in cellular responses.

Obligatory role of gamma interferon in T cell-replacing factor-dependent, antigen-specific murine B cell responses

The role of gamma interferon (IFN-gamma) in T cell-replacing factor (TRF) activity for antigen-specific plaque-forming cell (PFC) responses in vitro was studied using antibodies to murine IFN-gamma (Mu IFN-gamma). TRF activity was present in supernatants (Sn) of Con A- or mixed leukocyte reaction-stimulated murine spleen cells as well as in an IL-2-rich fraction of phytohemagglutinin-stimulated human peripheral blood lymphocyte Sn and in the Sn of the Gibbon T lymphoma MLA-144. The human TRF was highly active with cells from nu/nu mice and normal mice but not with cells from animals with the xid immunologic defect, similar to the activity of murine TRF. Antibodies to IFN-gamma consisted of hyper-immune rabbit antisera, IFN-gamma affinity-purified rabbit immunoglobulin and an interspecies hybridoma specific for Mu IFN-gamma. The results show that the activities of all preparations of TRF are markedly diminished or abrogated by antibody to Mu IFN-gamma but not by antibodies to human IFN-gamma (Hu IFN-gamma), nor by normal rabbit sera or purified rabbit Ig. The degree of inhibition was dose dependent and was quantitatively reversed by the addition to the cultures of recombinant-derived Mu IFN-gamma (Mu rIFN-gamma) but not Hu rIFN-gamma. This reversal was fully antigen specific and thus not attributable to polyclonal B cell activation by IFN-gamma, which is inactive alone in the TRF assay. Kinetic analysis shows that IFN-gamma must act by 24-48 h to produce PFC responses at 4 d. Together, the data demonstrate that IFN-gamma is a necessary mediator for TRF effects and that IFN-gamma is induced by TRF from T-depleted murine spleen cells in sufficient quantity to support large antibody responses. The source of this IFN-gamma may be the potent natural killer cells that are induced in cultures stimulated with TRF.

Cellular mechanism of primary anti-Thy-1 antibody responses in vitro induced by uniquely immunogenic thymocyte antigens

Thy-1 antigens are the only cell membrane antigens known to be able to induce primary antibody responses in vitro. We have shown that antigens from the thymocytes of mice and rats were highly immunogenic in cultures of murine spleen cells for the induction of Thy-1.1-specific plaque-forming cell responses, whereas antigens from other tissues, including brains and bone marrow, were poorly immunogenic, if at all. The thymocyte-specific Thy-1 immunogenicity was carried by disrupted cell membranes, and the specific activity for inducing responses was closely linked to Thy-1. We then tried to determine the mechanism of anti-Thy-1 antibody responses in vitro that were induced by the uniquely immunogenic thymocyte antigens. The thymocyte Thy-1 antigens behaved as T cell-independent class 2 (TI-2) antigens: they induced responses in athymic nude mice but not in CBA/N mice with a B cell defect. The apparent TI-2 responses to thymocyte Thy-1 did, however, require Thy-1+ cells in the responder, similar to anti-DNP-Ficoll responses. The full development of the anti-Thy-1 responses required the participation of splenic adherent cells (SAC). Nevertheless, the mechanism of the SAC dependency of anti-Thy-1 responses did not involve antigen presentation to lymphocytes by antigen-pulsed SAC, which contrasted with the finding that the presentation of antigen by live SAC to lymphocytes was indispensable for responses to DNP-Ficoll. The poor Thy-1 responsiveness of SAC-depleted spleen cells was fully restored by the addition of soluble factors (IL 1-like molecules) released from SAC into the culture, which did not replace the SAC-requirement of responses to DNP-Ficoll. It was concluded from these results that Thy-1 or Thy-1-linked structures on thymocyte membranes have an intrinsic activity to directly signal either TI-2 B cells or immature T cells, or both, for activation in the presence of soluble factors released from adherent accessory cells. This conclusion is discussed in relation to a hypothetical view that the thymocyte Thy-1 would physiologically mediate cell-to-cell interactions among special subsets of lymphocytes under thymic influence.

Cellular mechanism of primary anti-Thy-1 antibody responses in vitro induced by uniquely immunogenic thymocyte antigens

Thy-1 antigens are the only cell membrane antigens known to be able to induce primary antibody responses in vitro. We have shown that antigens from the thymocytes of mice and rats were highly immunogenic in cultures of murine spleen cells for the induction of Thy-1.1-specific plaque-forming cell responses, whereas antigens from other tissues, including brains and bone marrow, were poorly immunogenic, if at all. The thymocyte-specific Thy-1 immunogenicity was carried by disrupted cell membranes, and the specific activity for inducing responses was closely linked to Thy-1. We then tried to determine the mechanism of anti-Thy-1 antibody responses in vitro that were induced by the uniquely immunogenic thymocyte antigens. The thymocyte Thy-1 antigens behaved as T cell-independent class 2 (TI-2) antigens: they induced responses in athymic nude mice but not in CBA/N mice with a B cell defect. The apparent TI-2 responses to thymocyte Thy-1 did, however, require Thy-1+ cells in the responder, similar to anti-DNP-Ficoll responses. The full development of the anti-Thy-1 responses required the participation of splenic adherent cells (SAC). Nevertheless, the mechanism of the SAC dependency of anti-Thy-1 responses did not involve antigen presentation to lymphocytes by antigen-pulsed SAC, which contrasted with the finding that the presentation of antigen by live SAC to lymphocytes was indispensable for responses to DNP-Ficoll. The poor Thy-1 responsiveness of SAC-depleted spleen cells was fully restored by the addition of soluble factors (IL 1-like molecules) released from SAC into the culture, which did not replace the SAC-requirement of responses to DNP-Ficoll. It was concluded from these results that Thy-1 or Thy-1-linked structures on thymocyte membranes have an intrinsic activity to directly signal either TI-2 B cells or immature T cells, or both, for activation in the presence of soluble factors released from adherent accessory cells. This conclusion is discussed in relation to a hypothetical view that the thymocyte Thy-1 would physiologically mediate cell-to-cell interactions among special subsets of lymphocytes under thymic influence.

Inhibition of T cell proliferation by antibodies to synthetic peptides

While T cell proliferation to antigen in the presence of antigen-presenting cells is well known to be readily inhibited by antibodies directed against Class II major histocompatibility complex (MHC) (Ia/HLA-DR) products, it has not been possible to inhibit proliferation by antibodies directed against the antigen. Because of the implications of these observations for targets of T cell recognition, this phenomenon was reinvestigated using human T cell clones, recognizing a small (24 amino acid) synthetic peptide (termed p20) derived from the influenza hemagglutinin-1 molecule. It was found that proliferation of clones to p20 was inhibited efficiently (less than 90%), using p20 as antigen, and rabbit anti-p20. Inhibition was possible either by coculturing p20 antigen and antibody to p20 with cloned T cells and antigen-presenting (E-) cells, or by pulsing antigen-presenting cells with antigen prior to a brief incubation with antibody before washing the E- cells and using them to stimulate cloned T cells. These results do not indicate why previous attempts had failed, but in view of the different techniques available now (cloned T cells, small synthetic polypeptides, and antibody raised against polypeptide) we investigated the influence of these parameters. It was found that, using cloned T cells, the form of the antigen was of importance, as antibody inhibition of the response to hemagglutinin or whole influenza A was much less apparent. These differences were interpreted as being due to greater access of anti-p20 to p20 than to hemagglutinin or influenza. If uncloned T cell lines were used, inhibition was also much harder to detect. This was interpreted as masking of inhibition of the response of some clones in the line by interleukin 2-induced recruitment.