Dysregulated RASGRP1 expression through RUNX1 mediated transcription promotes autoimmunity

RasGRP1 is a Ras guanine nucleotide exchange factor, and an essential regulator of lymphocyte receptor signaling. In mice, Rasgrp1 deletion results in defective T lymphocyte development. RASGRP1-deficient patients suffer from immune deficiency, and the RASGRP1 gene has been linked to autoimmunity. However, how RasGRP1 levels are regulated, and if RasGRP1 dosage alterations contribute to autoimmunity remains unknown. We demonstrate that diminished Rasgrp1 expression caused defective T lymphocyte selection in C57BL/6 mice, and that the severity of inflammatory disease inversely correlates with Rasgrp1 expression levels. In patients with autoimmunity, active inflammation correlated with decreased RASGRP1 levels in CD4+ T cells. By analyzing H3K27 acetylation profiles in human T cells, we identified a RASGRP1 enhancer that harbors autoimmunity-associated SNPs. CRISPR-Cas9 disruption of this enhancer caused lower RasGRP1 expression, and decreased binding of RUNX1 and CBFB transcription factors. Analyzing patients with autoimmunity, we detected reduced RUNX1 expression in CD4+ T cells. Lastly, we mechanistically link RUNX1 to transcriptional regulation of RASGRP1 to reveal a key circuit regulating RasGRP1 expression, which is vital to prevent inflammatory disease.

Shp1 Loss Enhances Macrophage Effector Function and Promotes Anti-Tumor Immunity

Shp1, encoded by the gene Ptpn6, is a protein tyrosine phosphatase that transduces inhibitory signals downstream of immunoreceptors in many immune cell types. Blocking Shp1 activity represents an exciting potential immunotherapeutic strategy for the treatment of cancer, as Shp1 inhibition would be predicted to unleash both innate and adaptive immunity against tumor cells. Antibodies blocking the interaction between CD47 on tumor cells and SIRPα on macrophages enhance macrophage phagocytosis, show efficacy in preclinical tumor models, and are being evaluated in the clinic. Here we found that Shp1 bound to phosphorylated peptide sequences derived from SIRPα and transduced the anti-phagocytic signal, as Shp1 loss in mouse bone marrow-derived macrophages increased phagocytosis of tumor cells in vitro. We also generated a novel mouse model to evaluate the impact of global, inducible Ptpn6 deletion on anti-tumor immunity. We found that inducible Shp1 loss drove an inflammatory disease in mice that was phenotypically similar to that seen when Ptpn6 is knocked out from birth. This indicates that acute perturbation of Shp1 in vivo could drive hyperactivation of immune cells, which could be therapeutically beneficial, though at the risk of potential toxicity. In this model, we found that Shp1 loss led to robust anti-tumor immunity against two immune-rich syngeneic tumor models that are moderately inflamed though not responsive to checkpoint inhibitors, MC38 and E0771. Shp1 loss did not promote anti-tumor activity in the non-inflamed B16F10 model. The observed activity in MC38 and E0771 tumors was likely due to effects of both innate and adaptive immune cells. Following Shp1 deletion, we observed increases in intratumoral myeloid cells in both models, which was more striking in E0771 tumors. E0771 tumors also contained an increased ratio of effector to regulatory T cells following Shp1 loss. This was not observed for MC38 tumors, though we did find increased levels of IFNγ, a cytokine produced by effector T cells, in these tumors. Overall, our preclinical data suggested that targeting Shp1 may be an attractive therapeutic strategy for boosting the immune response to cancer via a mechanism involving both innate and adaptive leukocytes.

Protocol for Barcoding T Cells Combined with Timed Stimulations

Stimulation of naive T lymphocytes via the T cell receptor (TCR) induces distinct phosphorylation patterns that can be used to explore various signaling pathways within the cell. This protocol can be used to characterize different perturbations to the signaling pathways and the variations in time of stimulation. Here, we provide a method of barcoding and consolidating a maximum of 24 different sample conditions using two florescent dyes. This single sample for phospho-staining and flow cytometry saves time and reagents.

For complete details on the use and execution of this protocol, please refer to Krutzik and Nolan (2006), Krutzik et al. (2012), Vercoulen et al. (2017), Ksionda et al. (2018), and Myers et al. (2019).

•

Quantitative signaling analysis in primary T cells

•

Barcoding protocol for batch-wise processing

•

Minimizing experimental variation through batch experiments

•

A phospho-flow method amendable to other cell types

Active Tonic mTORC1 Signals Shape Baseline Translation in Naive T Cells

Naive CD4⁺ T cells are an example of dynamic cell homeostasis: T cells need to avoid autoreactivity while constantly seeing self-peptides, yet they must be primed to react to foreign antigens during infection. The instructive signals that balance this primed yet quiescent state are unknown. Interactions with self-peptides result in membrane-proximal, tonic signals in resting T cells. Here we reveal selective and robust tonic mTORC1 signals in CD4⁺ T cells that influence T cell fate decisions. We find that the Ras exchange factor Rasgrp1 is necessary to generate tonic mTORC1 signals. Genome-wide ribosome profiling of resting, primary CD4⁺ T cells uncovers a baseline translational landscape rich in mTOR targets linked to mitochondria, oxidative phosphorylation, and splicing. Aberrantly increased tonic mTORC1 signals from a Rasgrp1^Anaef allele result in immunopathology with spontaneous appearance of T peripheral helper cells, follicular helper T cells, and anti-nuclear antibodies that are preceded by subtle alterations in the translational landscape.

Myers et al. evaluate a mouse model of autoimmunity, Rasgrp1^Anaef. They find that T cells with the Rasgrp1^Anaef allele exhibit altered signaling from Rasgrp1 to the mTORC1 pathway in the basal state. They show that increased basal Rasgrp1^Anaef-mTORC1 signals lead to an altered translational landscape in T cells and immunopathology.

Allosteric Inhibition of SHP2 Stimulates Antitumor Immunity by Transforming the Immunosuppressive Environment

The protein tyrosine phosphatase SHP2 binds to phosphorylated signaling motifs on regulatory immunoreceptors including PD-1, but its functional role in tumor immunity is unclear. Using preclinical models, we show that RMC-4550, an allosteric inhibitor of SHP2, induces antitumor immunity, with effects equivalent to or greater than those resulting from checkpoint blockade. In the tumor microenvironment, inhibition of SHP2 modulated T-cell infiltrates similar to checkpoint blockade. In addition, RMC-4550 drove direct, selective depletion of protumorigenic M2 macrophages via attenuation of CSF1 receptor signaling and increased M1 macrophages via a mechanism independent of CD8⁺ T cells or IFNγ. These dramatic shifts in polarized macrophage populations in favor of antitumor immunity were not seen with checkpoint blockade. Consistent with a pleiotropic mechanism of action, RMC-4550 in combination with either checkpoint or CSF1R blockade caused additive antitumor activity with complete tumor regressions in some mice; tumors intrinsically sensitive to SHP2 inhibition or checkpoint blockade were particularly susceptible. Our preclinical findings demonstrate that SHP2 thus plays a multifaceted role in inducing immune suppression in the tumor microenvironment, through both targeted inhibition of RAS pathway-dependent tumor growth and liberation of antitumor immune responses. Furthermore, these data suggest that inhibition of SHP2 is a promising investigational therapeutic approach. SIGNIFICANCE: Inhibition of SHP2 causes direct and selective depletion of protumorigenic M2 macrophages and promotes antitumor immunity, highlighting an investigational therapeutic approach for some RAS pathway-driven cancers.

mTOR and other effector kinase signals that impact T cell function and activity

T cells play important roles in autoimmune diseases and cancer. Following the cloning of the T cell receptor (TCR), the race was on to map signaling proteins that contributed to T cell activation downstream of the TCR as well as co-stimulatory molecules such as CD28. We term this "canonical TCR signaling" here. More recently, it has been appreciated that T cells need to accommodate increased metabolic needs that stem from T cell activation in order to function properly. A central role herein has emerged for mechanistic/mammalian target of rapamycin (mTOR). In this review we briefly cover canonical TCR signaling to set the stage for discussion on mTOR signaling, mRNA translation, and metabolic adaptation in T cells. We also discuss the role of mTOR in follicular helper T cells, regulatory T cells, and other T cell subsets. Our lab recently uncovered that "tonic signals", which pass through proximal TCR signaling components, are robustly and selectively transduced to mTOR to promote baseline translation of various mRNA targets. We discuss insights on (tonic) mTOR signaling in the context of T cell function in autoimmune diseases such as lupus as well as in cancer immunotherapy through CAR-T cell or checkpoint blockade approaches.

Abstract 5019: Allosteric inhibition of SHP2 suppresses CSF1R signaling and selectively reduces viability of M2 tumor associated macrophages contributing to anti-tumor immunity

The protein-tyrosine phosphatase SHP2 promotes oncogenic RAS/MAPK pathway activation in different tumor types. In immune cells, SHP2 binds to phosphorylated ITIM and ITAM domains on regulatory receptors, including PD-1. We have shown that RMC-4550, a SHP2 allosteric inhibitor, attenuates tumor growth in syngeneic mouse tumor models with effects equivalent to, or greater than those of checkpoint inhibitors. Consistent with anti-tumor immunity as the mechanism, tumor growth inhibition (TGI) was not observed in immunocompromised mice. TGI was associated with changes in the tumor immune microenvironment, in both the adaptive and innate arms. Similar to checkpoint blockade, the frequency of CD8+T cell infiltrates was increased upon treatment with RMC-4550. Polarized macrophage populations were significantly shifted in favor of antitumor immunity, with marked increases in M1 and decreases in M2 cells, effects not seen with checkpoint blockade. The objective of the present study was to determine if the effect on tumor-associated macrophage (TAM) polarization is secondary to a release of the biochemical brakes on adaptive immunity and/or a result of a direct effect of SHP2 on TAMs.

In vivo administration of RMC-4550 in the CT26 syngeneic model significantly decreased M2, and increased M1, TAM after CD8+T cell depletion or IFNγ blockade, similar to the response in control animals. In vitro, SHP2 inhibition attenuated CSF1R signaling in murine bone marrow-derived macrophages and selectively induced apoptotic cell death in M2, but not M1, polarized macrophages. In addition, RMC-4550 treatment in vitro reduced the suppressive potential of human M-MDSCs. Collectively these observations suggest that SHP2 inhibition directly impacts the survival and function of suppressive monocytic immune cells. Given the effect of SHP2 inhibition on the CSF1R signaling pathway, we assessed whether the anti-tumor activity of RMC-4550 was similar to that of CSF1R blockade. In contrast to RMC-4550, anti-CSF1R antibody did not induce a significant delay in CT26 tumor growth. These results confirm that RMC-4550 has pleiotropic effects on the immune system including modulation of both adaptive and innate mechanisms. In summary, we propose that SHP2 plays a central role in inducing immune suppression in the tumor microenvironment by both inhibiting T cells and supporting the viability of pro-tumorigenic macrophages. Thus, SHP2 inhibition represents a novel investigational strategy with dual activity: direct inhibition of cancer cell growth in certain tumors as well as promotion of an anti-tumor immune response by direct transformation of the tumor immune microenvironment. Tumors that are intrinsically dependent upon SHP2 and exhibit a myeloid-rich microenvironment could be particularly susceptible to this dual-mechanism therapeutic strategy.

Citation Format: Elsa Quintana, Chris J. Schulze, Tiffany J. Choy, Darienne R. Myers, Kasia Mordec, Dylan Daniel, Mark A. Goldsmith, Jan A. Smith. Allosteric inhibition of SHP2 suppresses CSF1R signaling and selectively reduces viability of M2 tumor associated macrophages contributing to anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5019.

Abstract A103: Allosteric inhibition of SHP2 induces antitumor immunity in PD-1-sensitive tumors through modulation of both innate and adaptive mechanisms

The protein-tyrosine phosphatase SHP2, encoded by PTPN11, is a known oncogenic driver in a subset of cancers and a central signaling node in the RTK-RAS-MAPK pathway. Genetic and pharmacologic evidence supports a role for SHP2 in driving the proliferation of cancer cells dependent upon a range of activated RTKs, certain RAS and BRAF mutations, and NF1 loss of function mutations. In contrast, a role for SHP2 in antitumor immunity is not well established. SHP2 binds to phosphorylated ITIM and ITAM domains on regulatory receptors in immune cells and multiple reports have demonstrated a SHP2/PD-1 physical interaction. Recently it has been proposed that SHP2 transduces the PD-1 inhibitory checkpoint signal by direct de-phosphorylation of CD28. In this study we show that a peptide comprising two tyrosine phosphorylated 9-mers sequences from the PD-1 ITAM (connected by a PEG8 linker) can activate purified SHP2 enzyme. We also demonstrate that, like checkpoint inhibitors, allosteric inhibition of SHP2 activates NFAT-mediated gene expression in a reporter gene PD-1/PD-L1 bioassay. Based on these findings, we evaluated the impact of SHP2 inhibition on murine host immune cells and the tumor immune microenvironment in vivo using RMC-4550, a novel small-molecule allosteric inhibitor of SHP2. Oral daily administration of RMC-4550 significantly inhibited tumor growth in three syngeneic tumor models sensitive to checkpoint blockade. The inhibitory activity was comparable, and in some cases superior, to checkpoint inhibition. RMC-4550 did not inhibit growth in any of these cancer cell lines in vitro, suggesting that activity was not due to a tumor cell intrinsic antiproliferative effect. Rather, antitumor activity in vivo reflected modulation of murine host immune cell function. First, RMC-4550 did not inhibit tumor growth in immunocompromised Rag-2-deficient mice. Second, efficacy was significantly attenuated when CD8+T-cells were depleted in immunocompetent mice, suggesting that CD8+T-cells were important for tumor growth inhibition. Third, Shp2 inhibition had additive activity in combination with anti-CTLA4 or anti-PD-L1 treatment, resulting in complete tumor regression in some mice. Rechallenge studies also demonstrated the presence of immunologic memory induced by combination therapy. The additive activity with checkpoint blockade suggests an additional mechanism of action beyond inhibition of the checkpoint signal. Fourth, analysis of the immune landscape in the tumor microenvironment indeed revealed modulation of both adaptive and innate immune mechanisms. Similar to checkpoint blockade, RMC-4550 increased the frequency of CD8+T-cell infiltrates in tumors with a corresponding decrease in their PD-1 expression. In addition, Shp2 inhibition significantly shifted polarized macrophage populations by markedly increasing M1 and decreasing M2, effects not seen with anti-CTLA4 or anti-PD-L1. Collectively, these results suggest that SHP2 inhibition is not identical to that of checkpoint blockade and represents a novel investigational strategy that could leverage two antitumor mechanisms simultaneously: direct inhibition of cancer cell growth and modulation of the tumor microenvironment. Tumors that harbor oncogenic driver mutations sensitive to SHP2 and with established clinical sensitivity to checkpoint inhibitors could be of particular interest.

Citation Format: Elsa Quintana, Kasia Mordec, Robert J. Nichols, David Wildes, Chris J. Schulze, Darienne R. Myers, Mallika Singh, Elena Koltun, Adrian Gill, Stephen Kelsey, Mark A Goldsmith, Jan A.M. Smith. Allosteric inhibition of SHP2 induces antitumor immunity in PD-1-sensitive tumors through modulation of both innate and adaptive mechanisms [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A103.

Tonic LAT-HDAC7 Signals Sustain Nur77 and Irf4 Expression to Tune Naive CD4 T Cells

CD4⁺ T cells differentiate into T helper cell subsets in feedforward manners with synergistic signals from the T cell receptor (TCR), cytokines, and lineage-specific transcription factors. Naive CD4⁺ T cells avoid spontaneous engagement of feedforward mechanisms but retain a prepared state. T cells lacking the adaptor molecule LAT demonstrate impaired TCR-induced signals yet cause a spontaneous lymphoproliferative T helper 2 (T_H2) cell syndrome in mice. Thus, LAT constitutes an unexplained maintenance cue. Here, we demonstrate that tonic signals through LAT constitutively export the repressor HDAC7 from the nucleus of CD4⁺ T cells. Without such tonic signals, HDAC7 target genes Nur77 and Irf4 are repressed. We reveal that Nur77 suppresses CD4⁺ T cell proliferation and uncover a suppressive role for Irf4 in T_H2 polarization; halving Irf4 gene-dosage leads to increases in GATA3⁺ and IL-4⁺ cells. Our studies reveal that naive CD4⁺ T cells are dynamically tuned by tonic LAT-HDAC7 signals.

Tonic Signals: Why Do Lymphocytes Bother?

Since the 1990s it has been known that B and T lymphocytes exhibit low-level, constitutive signaling in the basal state (tonic signaling). These lymphocytes display a range of affinity for self, which in turn generates a range of tonic signaling. Surprisingly, what signaling pathways are active in the basal state and the functional relevance of the observed tonic signaling heterogeneity remain open questions today. Here we summarize what is known about the mechanistic and functional details of tonic signaling. We highlight recent advances that have increased our understanding of how the amount of tonic signal impacts immune function, describing novel tools that have moved the field forward and toward a molecular understanding of tonic signaling.

Rasgrp1 mutation increases naive T-cell CD44 expression and drives mTOR-dependent accumulation of Helios⁺ T cells and autoantibodies

Missense variants are a major source of human genetic variation. Here we analyze a new mouse missense variant, Rasgrp1^Anaef, with an ENU-mutated EF hand in the Rasgrp1 Ras guanine nucleotide exchange factor. Rasgrp1^Anaef mice exhibit anti-nuclear autoantibodies and gradually accumulate a CD44^hi Helios⁺ PD-1⁺ CD4⁺ T cell population that is dependent on B cells. Despite reduced Rasgrp1-Ras-ERK activation in vitro, thymocyte selection in Rasgrp1^Anaef is mostly normal in vivo, although CD44 is overexpressed on naïve thymocytes and T cells in a T-cell-autonomous manner. We identify CD44 expression as a sensitive reporter of tonic mTOR-S6 kinase signaling through a novel mouse strain, chino, with a reduction-of-function mutation in Mtor. Elevated tonic mTOR-S6 signaling occurs in Rasgrp1^Anaef naïve CD4⁺ T cells. CD44 expression, CD4⁺ T cell subset ratios and serum autoantibodies all returned to normal in Rasgrp1^AnaefMtor^chino double-mutant mice, demonstrating that increased mTOR activity is essential for the Rasgrp1^Anaef T cell dysregulation.

DOI:http://dx.doi.org/10.7554/eLife.01020.001

Our DNA contains more than three billion nucleotides. Each of these nucleotides can be an A, C, G or T, and groups of three neighboring nucleotides within our DNA are used to represent the 20 amino acids that are used to make proteins. This means that changing just one nucleotide can cause one amino acid to be replaced by a different amino acid in the protein encoded by that stretch of DNA: AAA and AAG code for the amino acid lysine, for example, but AAC and AAT code for asparagine. Known as missense gene variants, these changes can also increase or decrease the expression of the gene.

Every person has thousands of missense gene variants, including about 12,000 inherited from their parents. Sometimes these variants have no consequence, but they can be harmful if replacing the correct amino acid with a different amino acid prevents the protein from performing an important task. In particular, missense gene variants in genes that encode immune system proteins are likely to play a role in diseases of the immune system. For example, variants near a gene called Rasgrp1 have been linked to two autoimmune diseases – type 1 diabetes and Graves’ disease—in which the immune system mistakenly attacks the body’s own cells and tissues.

Now Daley et al. have shed new light on the mechanism by which a missense gene variant in Rasgrp1 can cause autoimmune diseases. Mice with this mutation show signs of autoimmune disease, but their T cells—white blood cells that have a central role in the immune system – develop normally despite this mutation. Instead, Daley et al. found that a specific type of T cell, called T helper cells, accumulated in large numbers in the mutant mice and stimulated cells of a third type—immune cells called B cells—to produce autoantibodies. The production of autoantibodies is a common feature of autoimmune diseases.

Daley et al. traced the origins of the T helper cells to excessive activity on a signaling pathway that involves a protein called mTOR, and went on to show that treatment with the drug rapamycin counteracted the accumulation of the T helper cells and reduced the level of autoimmune activity. In addition to exemplifying how changing just one amino acid change can have a profound effect, the work of Daley et al. is an attractive model for exploring how missense gene variants in people can contribute to autoimmune diseases.

DOI:http://dx.doi.org/10.7554/eLife.01020.002

Genome-wide translocation sequencing reveals mechanisms of chromosome breaks and rearrangements in B cells

Whereas chromosomal translocations are common pathogenetic events in cancer, mechanisms that promote them are poorly understood. To elucidate translocation mechanisms in mammalian cells, we developed high-throughput, genome-wide translocation sequencing (HTGTS). We employed HTGTS to identify tens of thousands of independent translocation junctions involving fixed I-SceI meganuclease-generated DNA double-strand breaks (DSBs) within the c-myc oncogene or IgH locus of B lymphocytes induced for activation-induced cytidine deaminase (AID)-dependent IgH class switching. DSBs translocated widely across the genome but were preferentially targeted to transcribed chromosomal regions. Additionally, numerous AID-dependent and AID-independent hot spots were targeted, with the latter comprising mainly cryptic I-SceI targets. Comparison of translocation junctions with genome-wide nuclear run-ons revealed a marked association between transcription start sites and translocation targeting. The majority of translocation junctions were formed via end-joining with short microhomologies. Our findings have implications for diverse fields, including gene therapy and cancer genomics.

Cementoblastoma associated with a primary tooth: a rare pediatric lesion

An intraosseous, slightly painful swelling was noted upon clinical examination of an eight-year-old girl. The swelling was of an unspecified duration and slow growing in nature. A radiopaque mass with a radiolucent periphery attached to the roots of the mandibular right second primary molar was noted on a periapical radiograph. The diagnosis of cementoblastoma was verified by the histologic assessment.

Performance of sealants applied to first permanent molars in a dental school setting

PURPOSE

The purpose of this study was to assess the performance of sealants placed by senior dental students as part of a comprehensive dental care program that included periodic patient recall.

METHODS

The dental records of 100 patients ranging in age from 6 to 13 years were selected for review to determine the treatments provided for first permanent molars over time. Criteria for inclusion were: 1) at least five documented recall examinations and 2) all four first permanent molars had to have been treated with an occlusal pit and fissure sealant. The data collected included: 1) the age of the patient at the time of initial sealant placement; 2) the subsequent treatment provided to the first permanent molars, including retreatment with sealant or restoration and the date the services were provided; 3) the last date of follow-up examination in the pediatric dental program.

RESULTS

A total of 400 molars were followed for an average of 54 months. Fifty-two percent of all molars received no further treatment after initial placement of sealant. Approximately 35% received retreatment with sealant only. The total number of molars receiving sealant material only was 343 (86%). The total number of teeth that were judged to require restoration was 57 (14%). No relationship was noted between the patient's age at placement of the occlusal sealant and sealant performance.

CONCLUSION

In a dental school clinic, occlusal sealants were effective at preventing caries in a comprehensive care program that included periodic recall.

An outcomes assessment of 15 years of patient care experiences in predoctoral pediatric dentistry

The purpose of this study was to examine the trends in numbers, demographic characteristics, and treatment history of pediatric dental patients under the care of dental students over the period 1980 through 1994. Data were collected for: exams, sealants, surfaces of amalgam, composite resin surfaces, pulpotomies, stainless steel crowns, and extractions. Correlations were done across the 15-year period to determine significant trends over time. During the 15-year period, the average number of patient visits required for each student to complete the requisite number of patients, declined from 45 appointments to complete 10 patients in 1980, to 35 visits to complete 13 patients in 1994. Over time, the numbers of amalgam surfaces, pulpotomies, extractions and stainless steel crowns decreased significantly, while the number of composite resin surfaces increased (P < 0.05). Based on a previous outcome assessment that indicated declining numbers of procedures performed between 1980 and 1985, the required number of patients treated per student was raised from 10 to 13, beginning with the 1986 class.

Dentists' perceptions of selected characteristics of their child patients

The purpose of this project was to examine the perceptions of both general and pediatric dentists regarding selected characteristics of the children they treat. A survey including questions on patients' ages, caries activity estimates, and types of patients treated was mailed once to a national random sample of 2,000 general and 1,000 pediatric dentists. The respondents provided a reasonable distribution by age and location, with the majority (69%) in practice more than 10 years. The pediatric dentists who responded perceive that they treat a younger population of child patients with more caries activity (P < 0.001), except in those patients older than 12 years. They also perceive that their patients pools include a larger percentage of patients with handicapping conditions (P < 0.01), behavior problems (P < 0.001) and patients who require treatment with general anesthesia (P < 0.001) than do the general dentists.

Dentists' perceptions of the variety of dental services provided for children

The purpose of this project was to describe the variety of dental services provided to child patients by general dentists and pediatric dentists. A survey was mailed to a random sample of 2000 general dentists and 1000 pediatric dentists requesting information about the dental services provided to children. Six hundred sixty-two general dentists (33 percent) and 492 pediatric dentists (49 percent) responded. Pediatric dentists reported more frequently obtaining informed consent (p < .0001), placing strip crowns (p < .0001), steel crowns (p < .0001) and pulp treatment procedures (p < .0001). Sealant use in both groups was high but the general dentists reported more frequently sealing occlusal surfaces with incipient caries (p < .001). There were differences in the reported provision of orthodontic services. The general dentists were more likely to refer children for treatment while the pediatric dentists reported they performed limited or comprehensive orthodontic treatment (p < .0001). The results of the survey demonstrate that pediatric dentists perceive that they provide a broader scope of restorative and orthodontic services.

The use of behavior management techniques by dentists across practitioner type, age, and geographic region

The purpose of this project was to describe the behavior management procedures employed for child dental patients based on practitioner type (general dentist vs. pediatric dentist), age, and geographic location. A survey of practice characteristics, which included questions relating to child behavior management, was mailed once to a national random sample of 3000 dentists--2000 general dentists and 1000 pediatric dentists. The pediatric dentists who responded employed a broader spectrum of management techniques than did the general dentists. Significant regional and practitioner age differences were reported in the use of behavior management techniques. The use of sedation and general anesthesia was reported more frequently in the western regions. Of the five age groups, the 40- to 49-year-old age group reported using the broadest spectrum of behavior management techniques. The survey revealed practitioner type, age, and regional differences in the child behavior management procedures employed by dentists.

Gender differences in the characteristics of dental services provided for children

The purpose of this project was to describe the differences and similarities in the practice of dentistry for children by male and female dentists. A once-mailed survey with a series of questions regarding the characteristics of their dental practices was sent to a random sample of 3,000 dentists. There were 1,154 useable responses (39 percent). Approximately 8 percent of the respondents were women, which is representative of the percentage of female dentists practicing in the United States. Chi square analysis was employed. There were differences in the practice characteristics of the male and female dentists responding to this survey. The female respondents were: significantly younger; had been in practice for a shorter period of time; more likely to be employees rather than solo practitioners; more likely to treat younger patients; less likely to do comprehensive orthodontic treatment and more likely to use physical restraints than their male counterparts.

Method of payment for children's dental services by practice type and geographic location

The purpose of this project was to evaluate practice type and geographical differences in methods of payment accepted for children's dental services. A survey was mailed to 2000 general dentists and 1000 pediatric dentists randomly selected to provide representation from the 50 United States. Dentists were asked to specify the type of practice and the state in which they primarily practice. The survey included Medicaid, dental insurance, preferred provider organizations (PPO), and self-payment as payment options. Dentists were asked to indicate whether they never, occasionally, or frequently accepted each option of payment for children's dental services. Responses were received from 1245 (42%) dentists, including 723 general dentists and 522 pediatric dentists. Chi-square statistical analysis revealed significant practice type and regional differences in the acceptance of Medicaid for payment. Pediatric dentists accept Medicaid more frequently than general dentists (P < 0.001). Most dentists accept dental insurance and self-payment, while few indicate involvement with a PPO. The study revealed significant practice type differences only in the acceptance of Medicaid as payment for children's dental services. On a geographic basis, there were significant differences in the acceptance of Medicaid and dental insurance.

Analyzing dental procedures performed by an HIV-positive dental student

No evidence of HIV transmission was found between an HIV-positive dental student and 163 treated patients.

The influence of practice type, region, and age on treatment recommendations for primary teeth

The purpose of this study was to investigate dentists' treatment recommendations for interproximal surfaces of primary molars based on the type of practitioner (general dentist or pediatric dentist), geographic location, and age of practitioner. Simulated cases, which included histories and pictures of bite-wing radiographs, were mailed to a random sample of 2000 general dentists and 1000 pediatric dentists. Dentists were asked to select their treatment recommendations for eight cases involving the interproximal surface of a specified primary molar. The return rate was 42% (1245) overall, with 36% (723) from general dentists and 52% (522) from pediatric dentists. An amalgam restoration was recommended most often for these eight cases. Dentists in the age 60+ category and pediatric dentists were more likely to recommend treatment for smaller interproximal lesions. Composite resins were recommended infrequently; however, dentists in the 60+ age category and dentists in the Northeast and Southwest were somewhat more likely to recommend composite resin than younger dentists, or dentists in other geographic locations. Dentists in the 40-49 age range, pediatric dentists, and dentists in the Southwest were the most likely to recommend stainless steel crowns. These simulated cases demonstrate differences and similarities in the treatment recommendations for interproximal lesions on primary molars based on age, practice type, and region.

A comparison of general dentists' and pediatric dentists' treatment recommendations for primary teeth

A survey which included a series of demographic questions, a brief clinical history, and pictures of eight radiographs was mailed to 2000 general dentists and 1000 pediatric dentists. Usable responses were received from 1369 (45%) dentists--765 (38%) general dentists, and 604 (60%) pediatric dentists. The dentists were asked to select the optimal treatment for a specified tooth in each radiograph. The results of this survey indicate that there were differences in the treatment recommendations of general and pediatric dentists. Whether or not pulp therapy was recommended, general dentists frequently recommended restoring teeth with amalgam. Pediatric dentists more frequently recommended restoring primary teeth with stainless steel crowns. There were differences in treatment recommendations within each group of practitioners, as well as between the two groups.

Management considerations for an HIV positive dental student

Health care workers who are HIV positive or who have AIDS are faced with unique and perplexing problems. Likewise dental students who are HIV positive present a special circumstance that demands review of ethical, legal, managerial, and medical considerations. The purpose of this paper is to describe the management considerations at the Medical College of Georgia following a recent report of an HIV positive dental student. The administration assembled a diverse team of experts for advice in the situation. This group assumed that the circumstance was a potential crisis with possible serious long-term implications. Therefore detailed planning, appropriate announcements, and careful management have been the administration's principle goal for several weeks. The key management strategies and actions are described from the time of notification of the student's HIV antibody test results through the initial testing of the patient population subgroup.

The role of race and ethnic status on the psychosocial correlates of smokeless tobacco use in adolescent males

From a stratified, random sampling of non-urban high schools in the Southeast, survey data were obtained from 5374 adolescent males. Over half reported trying smokeless tobacco, and approximately one third of these reported a regular, substantial level of use. The average age at initial use was 12.2 yr. and was negatively correlated with the level of use. Factor analysis of the psychosocial items resulted in four factors: substance use/deviant style, modeling, perceived negative consequences, and health behavior. Discriminant analysis of initial use indicated that substance use and modeling influences were the strongest predictors of trying smokeless tobacco. Regression analysis of level of smokeless tobacco use indicated that substance use, modeling, and perceived negative consequences were equivalent in their contribution. Separate analyses were performed for American Indian, Black, and White males. Although predictors of initial use were similar, level of smokeless tobacco use was most associated with the use of other substances in Blacks and with modeling influences in Whites.

Radiographic recommendations for the transitional dentition: comparison of general dentists and pediatric dentists

A survey which included brief case histories and intraoral photos of four transitional dentitions, including examples of ectopic and delayed eruption, as well as carious lesions, was mailed to a random sample of 2000 general dentists and 1000 pediatric dentists. Radiographic options were listed, from which each dentist was to indicate all films needed for each child's examination. Surveys were returned by 1273 (43%) dentists, including 713 (36%) general dentists and 560 (56%) pediatric dentists. The pediatric dentists took significantly more diagnostic radiographs than did the general dentists for each of the four transitional dentition cases. Pediatric dentists were more likely than the general dentists to take panoramic films and combinations which included panoramic films, bite-wing radiographs and periapical films. The most frequently ordered combinations were bite-wing radiographs plus panoramic films and bite-wing radiographs plus anterior periapical films. General dentists recommended bite-wing radiographs films only more frequently than did pediatric dentists. In view of the results of this study and the USDHHS guidelines for radiographic examinations, (1987) education must be provided for both general dentists and pediatric dentists regarding appropriate radiographic examinations for transitional dentition patients.

Comparing treatment options for occlusal surfaces utilizing an invasive index

The purpose of this project was to develop an invasive index to: 1) compare the treatments recommended by dentists for the occlusal surfaces of molars; 2) compare the invasive index score of each tooth with the extent of the carious lesion as determined by electrical resistance and histological examination; and 3) compare the relative extent of the total crown destruction resulting from the carious lesion and the cavity preparation. Twenty dentists examined 19 extracted permanent molar teeth using a #23 explorer and selected the most appropriate treatment from the following options: no treatment (score 0), occlusal sealant (score 1), preventive resin (score 2), occlusal amalgam (score 3). The invasive index scores determined for each dentist and each tooth were compared using an analysis of variance. The electrical conductivity of each tooth was measured with an electronic caries detector (Vanguard). Electrical resistance scores were compared to the invasive index scores and to a histological examination. The results demonstrate that the invasive index is a useful means to compare treatments recommended by different dentists. The invasive index suggests there is considerable variation among dentists in the treatment they recommend for occlusal surfaces. Electrical resistance testing did not provide helpful information for treatment planning of questionably carious occlusal surfaces.

Radiographic recommendations for the primary dentition: comparison of general dentists and pediatric dentists

A survey which included brief case histories and intraoral photos of four primary dentitions ranging from healthy to severely carious was mailed to a random sample of 2000 general dentists and 1000 pediatric dentists. Radiographic options were listed, from which the dentist was to indicate all films needed for each child's examination. Surveys were received from 1273 (43%) dentists, including 713 (36%) general dentists and 560 (56%) pediatric dentists. The pediatric dentists recommended significantly more diagnostic radiographs than did the general dentists across all four primary dentition cases. This trend was apparent in the absence of clinically visible caries. When radiographs were recommended, bite-wing radiographs were the most frequently ordered films. The most frequently ordered combination among all respondents was bite-wing radiographs plus anterior periapical films. The results suggest that, frequently, neither general dentists nor pediatric dentists prescribe radiographs for the primary dentition patient that conform to the USDHHS guidelines for radiographic examination (1987).

Smokeless tobacco use in adolescent females: prevalence and psychosocial factors among racial/ethnic groups

From a stratified, random sampling of Southeastern, nonurban high schools, survey data on smokeless tobacco use and potential psychosocial risk factors were obtained from 5683 adolescent females. Of the 15.3% who reported trying smokeless tobacco, most (75%) reported only experimental use. Factor analysis of the psychosocial items resulted in four factors: perceived negative consequences, substance use, modeling, and active lifestyle. Discriminant analysis on use indicated that modeling influences and use of other substances were the strongest predictors of initial smokeless tobacco use. Level of use, however, was most strongly associated with lower perceived negative consequences for use and the use of other substances. Separate analyses on American Indian, Black, and White subgroups suggested that factors associated with initial use were similar but that substantial differences exist between subgroups on risk factors for level of smokeless tobacco use.

Typology and correlates of smokeless tobacco use

The incidence, use patterns, and correlates of smokeless tobacco have become increasingly important as usage rates rise and harmful health effects become established. The present study assessed the incidence of smokeless tobacco use in a Southeastern U.S. sample and selected correlates of use. From the responses of 3725 high school students, 19.9% reported trying smokeless tobacco products (35.5% for males, 5.8% for females). Most agreed that tobacco use has harmful health consequences. Those disagreeing with these health beliefs were more likely to use smokeless tobacco. Cigarette smoking was strongly associated with initial use. Of those reporting any use of smokeless tobacco, most used it for less than an hour per day, but 18% reported 3 or more hours of use per day. Forty-four percent reported a first use of smokeless tobacco before 13 years of age. Early initial use was associated with greater frequency and duration of use. Early initial users also reported greater influence from family and advertisements. Encouragement from friends, however, appeared to be the major factor regardless of age at initial use. Of particular concern is that 8.4% of those having any experience with smokeless tobacco felt they were addicted to the substance. Finally, 27.9% reported swallowing the substance or spittle, suggesting the need for further research on the potential health implications of this behavior.

Localized prepubertal periodontitis: literature review and report of case

This case describes a young, healthy, white female who demonstrated anterior alveolar bone loss along with premature loss of her primary incisors. The alveolar bone loss remains unexplained. The root surfaces of most of the primary anterior teeth exhibited one or more eroded areas devoid of cementum with some evidence in two teeth of cellular resorptive activity. These findings suggest that premature root resorption was occurring concurrently with unexplained extensive alveolar bone loss. The child will be examined periodically to determine whether this process of bone loss with subsequent tooth loss will involve additional primary or permanent teeth.

Clinical performance of sealed composite restorations placed over caries compared with sealed and unsealed amalgam restorations

The 2-year clinical evaluations of paired occlusal restorations are presented. Each study participant received a sealed composite restoration placed over a carious lesion and either a traditional outline-form (unsealed) amalgam or an ultraconservative sealed amalgam restoration. Caries was removed before placement of both types of amalgam restorations. No important clinical differences developed among the three groups of restorations.

Dental radiology for children

The benefit for the child from the judicious use of diagnostic dental radiography is improved dental health. The risk to the child from dental diagnostic radiation exposure appears to be extremely low. Despite the low risk, the dentist must minimize the child's exposure to ionizing radiation by using sound clinical judgment to determine what radiographs are necessary and to provide children with optimal protection from ionizing radiation.

Marital disturbance and child problems: a cautionary note regarding hyperactive children

In previous work, investigators have found a relationship between marital discord and childhood conduct problems (aggression) in clinic samples. Given the wide variability of aggression found among hyperactive children, it would follow from previous work that child aggression may be associated with marital discord in a hyperactive population. This hypothesis was tested in a sample of 23 boys (ages 5 to 8) diagnosed as attention deficit with hyperactivity. Aggressive behaviors were tracked by the children's teachers for 12 school days. Parental and teacher ratings of conduct problems were also obtained. Additionally, the auditory version of the laboratory Continuous Performance Test was administered. Marital adjustment, overt hostility, and conflict tactics, as reported by the mothers, were not significantly correlated with any of the measures of aggression or conduct problems. In other words, marital discord in families with a hyperactive boy did not explain differential rates of aggressive behavior despite definite variability in both the marital and child behavioral measures. Marital discord was marginally related to severity of attentional deficit on the Continuous Performance Test. The results underscore the need for caution in attempting to extend findings from a general population (i.e., undifferentiated clinic-referred children) to a specific diagnostic subgroup (i.e., attention-deficit hyperactive children).