Abstract 3027: Dissecting mechanisms of anti-PD-1 therapy with massively parallel single-cell RNA-sequencing

Anti-PD-1 therapy is an important new treatment option for many different types of malignancies, but overall response rates are less than 40%. Limited understanding of how anti-PD-1 treatment changes the tumor immune microenvironment is a barrier to identifying rational combination therapies and understanding mechanisms of immunotherapy resistance. To overcome this barrier, we set out to understand the mechanisms by which anti-PD-1 therapy augments the anti-tumor immune response using single-cell genomics. We have developed a massively parallel single-cell RNA-sequencing platform (“Seq-Well”) that uses a fabricated chip with nearly 100,000 nanowells into which barcoded beads and individual cells are distributed prior to lysis and RNA capture. We used this platform to comprehensively define the global expression profile of all major immune lineages in the tumor microenvironment in a mouse tumor model of immunotherapy. Mice were implanted with the B16F10 melanoma transplantable model of cancer and treated with anti-PD-1 or control antibodies. Tumors were harvested and CD45+ tumor-infiltrating leukocytes isolated by FACS. In a single experiment we were able to sequence the transcriptomes of over 600 individual cells, allowing us to clearly distinguish different immune lineages within the tumor microenvironment. We detect two transcriptionally distinct populations of CD8+ T cells, one that is highly proliferative (as marked by Ki-67), and one that has higher expression of cytotoxic markers (i.e. perforin). The Ki-67hi population is enriched for a gene expression signature from terminally exhausted CD8+ T cells in chronic viral infection, suggesting that this is a more exhausted subset. Treatment with anti-PD-1 globally alters the tumor microenvironment, including enriching for CD8+ T cells in the Prfhi subpopulation compared with the Ki-67hi more terminally exhausted population. Studies to understand changes in the immune infiltrate of immunotherapy resistant tumors are currently ongoing. In conclusion, massively parallel single-cell RNA-sequencing allows us to dissect the mechanisms by which checkpoint blockade controls tumor growth, revealing shifts in the differentiation state of exhausted CD8+ T cells induced by checkpoint blockade.

Citation Format: Brian C. Miller, Marc H. Wadsworth, Kevin Bi, Travis K. Hughes, Robert Manguso, Arlene H. Sharpe, Alex K. Shalek, Nicholas Haining. Dissecting mechanisms of anti-PD-1 therapy with massively parallel single-cell RNA-sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3027. doi:10.1158/1538-7445.AM2017-3027

Abstract 1019: In vivo CRISPR screening identifies Ptpn2 as a target for cancer immunotherapy

Despite the dramatic clinical success of cancer immunotherapy with PD-1 checkpoint blockade, most patients don’t experience sustained clinical benefit, suggesting that additional therapeutic strategies are needed. Functional genomic screens in cancer cells to discover new therapeutic targets are usually carried out in vitro where interaction with the immune system is absent. Here we report a pooled, loss-of-function genetic screening approach using CRISPR/Cas9 genome editing that is conducted in vivo in mouse transplantable tumors treated with vaccination and PD-1 checkpoint blockade. We tested 2,400 genes expressed by melanoma cells for those that synergize with or cause resistance to checkpoint blockade, and recovered the known immune evasion molecules, PD-L1 and CD47. Loss of function of multiple genes required to sense interferon-y caused resistance to immunotherapy. Deletion of Ptpn2, a pleotropic protein tyrosine phosphatase improved response to immunotherapy. In vivo, Ptpn2 deficient tumors showed increased infiltration of activated CD8+T cells. In vitro, Ptpn2 loss by tumor cells increased antigen presentation to T cells. Biochemical, transcriptional and genetic epistasis experiments demonstrated that loss of function of Ptpn2 sensitizes tumors to immunotherapy by enhancing interferon-y-mediated effects on the tumor cell. Thus, augmenting interferon-y signaling in tumor cells could increase the efficacy of immunotherapy. More generally, in vivo genetic screens in tumor models can identify new immunotherapy targets and rationally prioritize combination therapies.

Citation Format: Robert T. Manguso, Hans W. Pope, Margaret D. Zimmer, Flavian D. Brown, Kathleen B. Yates, Brian C. Miller, Natalie B. Collins, Kevin Bi, Martin W. Lafleur, Vikram R. Juneja, Sarah A. Weiss, David E. Fisher, David E. Root, Arlene H. Sharpe, John G. Doench, W Nicholas Haining. In vivo CRISPR screening identifies Ptpn2 as a target for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1019. doi:10.1158/1538-7445.AM2017-1019

Abstract PR11: Dissecting mechanisms of PD-1 blockade with single-cell RNA-sequencing

Anti-PD-1 therapy is an important new treatment option for many different types of malignancies, but overall response rates are less than 40%. We do not yet understand which patients will benefit and what resistance mechanisms allow tumor escape. The goal of this work is to understand the mechanisms by which anti-PD-1 therapy augments the anti-tumor immune response at the cellular level. Given that anti-PD-1 therapy is thought to work by altering the immunosuppressive tumor microenvironment, efforts to improve its efficacy will require a deep understanding of this complicated milieu. This will require analysis of thousands of cells using methodology that avoids the pitfalls of current techniques that have either limited scope - flow cytometry, immunohistochemistry - or limited resolution - bulk RNA sequencing. To this end, we have developed a massively parallel single-cell RNA-sequencing platform (Seq-Well) that comprehensively defines the global expression profile of all major immune lineages in the tumor microenvironment. Seq-Well uses a fabricated chip with nearly 100,000 nanowells into which barcoded beads and individual cells are distributed prior to lysis and RNA capture. Mice were implanted with two different transplantable models of cancer (MC38 colon carcinoma or B16 melanoma) and treated with anti-PD-1 or control antibodies. Tumors were harvested and CD45+ tumor-infiltrating leukocytes isolated by FACS. Thousands of cells were sequenced using Seq-Well with a median recovery of approximately 1,000 genes/cell. This level of expression diversity allows us to clearly distinguish different cell populations within the tumor microenvironment. We detect two transcriptionally distinct populations of CD8+ T cells, one that is highly proliferative (as marked by Ki-67), and one that has higher expression of perforin and TIM-3. The Ki-67+ population is enriched for a gene expression signature characterized by effector CD8+ T cells early in viral infection, consistent with their more proliferative nature. We hypothesize that this cluster of CD8+ T cells is also more functional given this signature enrichment and its lower expression of TIM-3, a marker found on exhausted CD8+ T cells. Comparisons of anti-PD-1 treated and control treated tumors are ongoing. In conclusion, massively parallel single-cell RNA-sequencing is a promising technology for the analysis of tumor immune infiltrates that will allow us to address the mechanisms by which checkpoint blockade controls tumor growth. By advancing our knowledge of an important immune checkpoint therapy, we aim to better understand who will respond to therapy, what resistance mechanisms may develop, and how to augment therapeutic efficacy with additional treatments.

This abstract is also being presented as Poster A79.

Citation Format: Brian C. Miller, Marc H. Wadsworth 2nd, Kevin Bi, Travis K. Hughes, Arlene H. Sharpe, Alex K. Shalek, W. Nicholas Haining. Dissecting mechanisms of PD-1 blockade with single-cell RNA-sequencing. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr PR11.

CD19-Targeted CAR T Cells: A New Tool in the Fight against B Cell Malignancies

Adoptive cell immunotherapy is a novel tool in the fight against cancer. Serving both effector and memory functions for the immune system, T cells make an obvious candidate for adoptive cell immunotherapy. By modifying native T cells with a chimeric antigen receptor (CAR), these cells can theoretically be targeted against any extracellular antigen. To date, the best-studied and clinically validated CAR T cells recognize CD19, a cell surface molecule on B cells and B cell malignancies. These CD19-directed T cells have shown clinical utility in chronic lymphocytic leukemia, acute lymphoblastic leukemia (ALL), and non-Hodgkin's lymphomas, with some patients achieving long-term disease remissions after treatment. This review will briefly summarize the current data supporting the use of adoptively transferred CAR T cells for the treatment of CD19-positive malignancies. Given these exciting results, the Food and Drug Administration has granted a 'breakthrough' designation for several variations of CD19-directed CAR T cells for treatment of adult and pediatric relapsed/refractory ALL.

Invariant NKT cells require autophagy to coordinate proliferation and survival signals during differentiation

Autophagy regulates cell differentiation, proliferation, and survival in multiple cell types, including cells of the immune system. In this study, we examined the effects of a disruption of autophagy on the differentiation of invariant NKT (iNKT) cells. Using mice with a T lymphocyte-specific deletion of Atg5 or Atg7, two members of the macroautophagic pathway, we observed a profound decrease in the iNKT cell population. The deficit is cell-autonomous, and it acts predominantly to reduce the number of mature cells, as well as the function of peripheral iNKT cells. In the absence of autophagy, there is reduced progression of iNKT cells in the thymus through the cell cycle, as well as increased apoptosis of these cells. Importantly, the reduction in Th1-biased iNKT cells is most pronounced, leading to a selective reduction in iNKT cell-derived IFN-γ. Our findings highlight the unique metabolic and genetic requirements for the differentiation of iNKT cells.

Autophagy proteins regulate the secretory component of osteoclastic bone resorption

Osteoclasts resorb bone via the ruffled border, whose complex folds are generated by secretory lysosome fusion with bone-apposed plasma membrane. Lysosomal fusion with the plasmalemma results in acidification of the resorptive microenvironment and release of CatK to digest the organic matrix of bone. The means by which secretory lysosomes are directed to fuse with the ruffled border are enigmatic. We show that proteins essential for autophagy, including Atg5, Atg7, Atg4B, and LC3, are important for generating the osteoclast ruffled border, the secretory function of osteoclasts, and bone resorption in vitro and in vivo. Further, Rab7, which is required for osteoclast function, localizes to the ruffled border in an Atg5-dependent manner. Thus, autophagy proteins participate in polarized secretion of lysosomal contents into the extracellular space by directing lysosomes to fuse with the plasma membrane. These findings are in keeping with a putative link between autophagy genes and human skeletal homeostasis.

Identification of Atg5-dependent transcriptional changes and increases in mitochondrial mass in Atg5-deficient T lymphocytes

Autophagy is implicated in many functions of mammalian cells such as organelle recycling, survival and differentiation, and is essential for the maintenance of T and B lymphocytes. Here, we demonstrate that autophagy is a constitutive process during T cell development. Deletion of the essential autophagy genes Atg5 or Atg7 in T cells resulted in decreased thymocyte and peripheral T cell numbers, and Atg5-deficient T cells had a decrease in cell survival. We employed functional-genetic and integrative computational analyses to elucidate specific functions of the autophagic process in developing T-lineage lymphocytes. Our whole-genome transcriptional profiling identified a set of 699 genes differentially expressed in Atg5-deficient and Atg5-sufficient thymocytes (Atg5-dependent gene set). Strikingly, the Atg5-dependent gene set was dramatically enriched in genes encoding proteins associated with the mitochondrion. In support of a role for autophagy in mitochondrial maintenance in T lineage cells, the deletion of Atg5 led to increased mitochondrial mass in peripheral T cells. We also observed a correlation between mitochondrial mass and Annexin-V staining in peripheral T cells. We propose that autophagy is critical for mitochondrial maintenance and T cell survival. We speculate that, similar to its role in yeast or mammalian liver cells, autophagy is required in T cells for the removal of damaged or aging mitochondria and that this contributes to the cell death of autophagy-deficient T cells.

The autophagy gene ATG5 plays an essential role in B lymphocyte development

Macroautophagy (herein autophagy) is an evolutionarily conserved process, requiring the gene ATG5, by which cells degrade cytoplasmic constituents and organelles. Here we show that ATG5 is required for efficient B cell development and for the maintenance of B-1a B cell numbers. Deletion of ATG5 in B lymphocytes using Cre-LoxP technology or repopulation of irradiated mice with ATG5-/- fetal liver progenitors resulted in a dramatic reduction in B-1 B cells in the peritoneum. ATG5-/- progenitors exhibited a significant defect in B cell development at the pro- to pre-B cell transition, although a proportion of pre-B cells survived to populate the periphery. Inefficient B cell development in the bone marrow was associated with increased cell death, indicating that ATG5 is important for B cell survival during development. In addition, B-1a B cells require ATG5 for their maintenance in the periphery. We conclude that ATG5 is differentially required at discrete stages of development in distinct, but closely related, cell lineages.

Coronavirus replication does not require the autophagy gene ATG5

Macroautophagy (herein autophagy) is a cellular process, requiring ATG5, by which cells deliver double membrane-bound packets containing cytoplasm or cytoplasmic organelles to the lysosome. This process has been reported in some cases to be antiviral, while in other cases it has been reported to be required for efficient viral replication or release. A role for autophagy in RNA virus replication has been an attractive hypothesis because of the association of RNA virus replication with complex membrane rearrangements in the cytoplasm that can generate opposed double membranes. In this study we demonstrate that ATG5 is not required for murine hepatitis virus (MHV) replication n either bone marrow derived macrophages (BMMphi) lacking ATG5 by virtue of Crerecombinase ediated gene deletion or primary low passage murine ATG5(-/-) embryonic ibroblasts (pMEFs). We conclude that neither ATG5 nor an intact autophagic pathway re required for MHV replication or release.

Dating age and stage as correlates of adolescent sexual attitudes and behavior

Dating experiences, especially the type or stage of dating, have consistently been found to be related to premarital sexual behavior. Findings regarding the age at 1st date and sexual behavior have been less consistent. This paper examined the age at which dating began and the type of dating relationship as correlates of premarital sexual attitudes and behavior among mid-teen adolescents. The analyses were based on a sample of high school students (n=836), most of whom were between the ages of 15 and 18 when the surveys were conducted. Early dating, especially early steady dating, was related to permissive attitudes and to premarital sexual experience among both males and females. The relationship between early dating and intercourse experience was particulary strong among Mormons, a religious group which has institutionalized age 16 as the legitimate age to begin dating.

Academic goals, achievement, and age at first sexual intercourse: longitudinal, bidirectional influences

This study examined bidirectional relationships between age at first sexual intercourse and academic goals and achievement. It was hypothesized that lower educational goals and achievement would be associated with initiating sexual intercourse at a younger age, and that initiating sexual activity early would be associated with a decrease in subsequent academic achievement and goals. In longitudinal data spanning 11 years, evidence was found for bidirectional effects. One interpretation of these results is that adolescents with high educational goals and achievement delay having intercourse because of the perceived risks (e.g., pregnancy and sexually transmitted diseases may jeopardize their plans for the future). Conversely, adolescents who engage in sexual intercourse at young ages might undergo a change in attitudes, including reduced interest in academic achievement and goals. The specific educational variables most strongly related to adolescent sexual intercourse in this study differed substantially by race and gender.

Comparisons of adopted and nonadopted adolescents in a large, nationally representative sample

There are conflicting findings about whether adopted children have more psychological and behavioral problems than nonadoptees. Research results are discrepant partly because many previous studies were based on small clinical samples or on samples biased by self-selection. A nationally representative school survey (Add Health) was used to compare adopted (n = 1,587) and nonadopted adolescents (total N = 87,165) across a wide variety of measures. Standardized mean differences show that adopted adolescents are at higher risk in all of the domains examined, including school achievement and problems, substance use, psychological well-being, physical health, fighting, and lying to parents. Demographic and background variable breakdowns show that the effect sizes for differences between adopted and nonadopted adolescents were larger for males, younger or older adolescents, Hispanics or Asians, and adolescents living in group homes or with parents of low education. Distributional analyses revealed approximately a 1:1 ratio of adopted to nonadopted adolescents in the middle ranges of the outcome variables but a ratio of 3:1 or greater near the tails of the distributions. These data clearly show that more adopted adolescents have problems of various kinds than their nonadopted peers; effect sizes were small to moderate based on mean differences, but comparisons of distributions suggest much larger proportions of adopted than nonadopted adolescents at the extremes of salient outcome variables.

Adopted adolescents' overrepresentation in mental health counseling: adoptees' problems or parents' lower threshold for referral?

A larger proportion of adopted adolescents receive mental health counseling than do their nonadopted peers. Adoptees might have more problems that require counseling, or their adoptive parents might have a lower threshold for referral (or both).

OBJECTIVE

To test the hypothesis that both the extent of adolescents' problems and their adoption status would predict whether adolescents received psychological counseling, after controlling for family demographic characteristics.

METHOD

Two large data sets collected from 1994 through 1996 by the National Longitudinal Study of Adolescent Health (Add Health) were used. In parallel analyses of the 2 data sets, hierarchical logistic regression models were implemented to assess the incremental effects of problem behaviors, family characteristics, and adoption status on adolescents receiving counseling.

RESULTS

Selected adolescents' problems and family demographic characteristics were significant predictors for having received counseling, but, after controlling for these variables, adoptees were still about twice as likely as nonadoptees to have received counseling.

CONCLUSIONS

Prevalence of problems, adoptive family characteristics, and adoption status must all be taken into account to understand why adoptees are more likely to receive counseling. Clinicians should be sensitive to issues that are especially salient in adoptive families.

Changes in reports and incidence of child abuse following natural disasters

OBJECTIVE

The aim of this research was to investigate if there is a higher incidence of child abuse following major natural disasters.

METHODOLOGY

Child abuse reports and substantiations were analyzed, by county, for 1 year before and after Hurricane Hugo, the Loma Prieta Earthquake. and Hurricane Andrew. Counties were included if damage was widespread, the county was part of a presidential disaster declaration, and if there was a stable data collection system in place.

RESULTS

Based on analyses of numbers, rates, and proportions, child abuse reports were disproportionately higher in the quarter and half year following two of the three disaster events (Hurricane Hugo and Loma Prieta Earthquake).

CONCLUSIONS

Most, but not all, of the evidence presented indicates that child abuse escalates after major disasters. Conceptual and methodological issues need to be resolved to more conclusively answer the question about whether or not child abuse increases in the wake of natural disasters. Replications of this research are needed based on more recent disaster events.

Comparisons of adopted and nonadopted adolescents in a large, nationally representative sample

There are conflicting findings about whether adopted children have more psychological and behavioral problems than nonadoptees. Research results are discrepant partly because many previous studies were based on small clinical samples or on samples biased by self-selection. A nationally representative school survey (Add Health) was used to compare adopted (n = 1,587) and nonadopted adolescents (total N = 87,165) across a wide variety of measures. Standardized mean differences show that adopted adolescents are at higher risk in all of the domains examined, including school achievement and problems, substance use, psychological well-being, physical health, fighting, and lying to parents. Demographic and background variable breakdowns show that the effect sizes for differences between adopted and nonadopted adolescents were larger for males, younger or older adolescents, Hispanics or Asians, and adolescents living in group homes or with parents of low education. Distributional analyses revealed approximately a 1:1 ratio of adopted to nonadopted adolescents in the middle ranges of the outcome variables but a ratio of 3:1 or greater near the tails of the distributions. These data clearly show that more adopted adolescents have problems of various kinds than their nonadopted peers; effect sizes were small to moderate based on mean differences, but comparisons of distributions suggest much larger proportions of adopted than nonadopted adolescents at the extremes of salient outcome variables.

Identification of gamma-endorphin-generating enzyme as insulin-degrading enzyme

The EL-4 thymoma cell line contains a peptidase which converts beta-endorphin to beta-endorphin 1-17 (gamma-endorphin), beta-endorphin 1-18, and their corresponding C-terminal fragments. This enzyme was purified approximately 700-fold to a single band on an SDS-polyacrylamide gel (106 kDa) in 16% yield. Estimation of the native molecular weight by molecular sieve chromatography gave a value of approximately 220 kDa, indicating that this enzyme is a dimer. Peptide sequencing demonstrated this activity can be attributed to insulin degrading enzyme, a previously described member of the inverzincin family (Hooper, 1994). Kinetic studies with a number of peptide substrates indicate that the enzyme preferentially cleaves on the amino side of hydrophobic or basic residues. However, the substrate specificity is more complex since not all basic and hydrophobic residues in a peptide are cleaved. The enzyme exhibits a requirement for a P'2 residue. On the basis of kcat/K(m) values, insulin, growth hormone releasing factor, and beta-endorphin are nearly equivalent substrates for the enzyme; however, growth hormone releasing factor and beta-endorphin exhibit a 40-fold higher kcat, but a 10-fold decreased affinity relative to insulin. A role for insulin-degrading enzyme as both a beta-endorphin-processing and -inactivating enzyme is implicated from these studies.

A secreted peptidase involved in T cell beta-endorphin metabolism

Beta-endorphin metabolism by CD4+ and CD8+ T cells, and the thymoma cell line, EL4, was investigated. In all three cell types, extracellular beta-endorphin was metabolized exclusively by a secreted, metal-dependent, thiol peptidase. The enzyme activity is expressed constitutively in EL4 cells and following activation of CD4+ and CD8+ T cells with anti-CD3 antibody. The enzyme is not one of the proteinases associated with cytolytic T cells and does not appear to be identical with any previously described beta-endorphin metabolizing enzyme. The enzyme cleaves beta-endorphin at approximately equal rates at either of two sites to yield beta-endorphin(1-17) (which is gamma-endorphin), beta-endorphin(1-18), beta-endorphin(18-31) and beta-endorphin(19-31). Evidence in the literature indicates that these N- and C-terminal peptides which contain, respectively, the opioid and non-opioid receptor binding domains of beta-endorphin, are biologically active. Thus, it is likely that this new T cell peptidase has important immunoregulatory activity.

The effects of forced sexual intercourse on white female adolescents

In the 1987 National Survey of Children the question was asked: "Was there ever a time when you were forced to have sex against your will, or were you raped?" Among White females, aged 18-22, those who answered yes (n = 41) and no (n = 400) were compared on a number of social-psychological and sexual variables that might be thought of as outcomes affected by having had coercive sexual experience(s). Those who reported being forced to have sexual intercourse, compared to those who did not, had more permissive attitudes about 16-17-year-olds having intercourse and a younger age of first voluntary sexual intercourse themselves. They also had lower internal locus of control and higher depression scores, and they needed and received more psychological help than those not reporting forced sexual intercourse. Dividing the forced sexual intercourse group (FSI) into those reporting FSI before versus after their first date, and those whose FSI was before versus after age 12, yielded essentially the same findings. Even in the presence of multivariate control variables. FSI experience remained a significant predictor of age at first voluntary sexual intercourse, locus of control, depression, and perceived need for psychological help. These analyses of national survey data support the clinical perspective that forced sexual intercourse causes or exacerbates various sexual and psychological problems.

In vivo effects of lipopolysaccharide on hepatic free-NAD(P)(+)-linked redox states and cytosolic phosphorylation potential in 48-hour-fasted rats

This study was performed to determine the magnitude and time of onset of in vivo changes in hepatic bioenergetics in response to a sublethal dose of lipopolysaccharide (LPS), a bacterial endotoxin. Male rats (48-hour-fasted) were administered an intraperitoneal injection of LPS (5 mg/kg body weight) or vehicle alone, and the livers were freeze-clamped 5, 30, or 180 minutes or 24 hours later. Liver tissue was extracted with perchloric acid, and the metabolites necessary to calculate NAD(+)- and NADP(+)-linked redox states and the cytosolic phosphorylation potential were measured. There was no significant difference in hepatic cytosolic phosphorylation potential between LPS and control groups at any of the times investigated. This indicated that the ability of the liver to synthesize adenosine triphosphate (ATP) was not compromised under the conditions of the study. No changes in hepatic redox states were observed 5 or 30 minutes after LPS treatment. Three hours after LPS treatment, hepatic cytosolic and mitochondrial free-[NAD+]/[NADH] redox states and the cytosolic free-[NADP+]/[NADPH] redox state were more oxidized. By 24 hours, only NAD(+)-linked redox states were more oxidized than the time-matched controls. Hepatic urea content was elevated at both 3 and 24 hours, compatible with an increased rate of urea synthesis as a consequence of increased amino acid metabolism, whereas hepatic beta-hydroxybutyrate and total ketone bodies were decreased 24 hours after LPS treatment, indicating decreased hepatic ketogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics of effective day treatment programming for persons with borderline personality disorder

Day treatment, or partial hospitalization, may have unique advantages for the treatment of patients with borderline personality disorder. Such treatment may offer patients the optimal level of intensiveness and containment, resulting in less regressive dependency and acting-out behavior. To be successful in treatment of patients with borderline personality disorder, a day treatment program should facilitate the patient's need to experience and express affect safely, optimize the program's ability to provide less restrictiveness than inpatient treatment but more sustained and intensive support than outpatient treatment, and use verbal and nonverbal approaches to help patients maintain primary responsibility for their well-being. A length of stay of three weeks allows patients to regain baseline functioning and resume long-term outpatient care. Treatment goals should be clear and resolvable in three weeks.

Methionine enkephalin is hydrolyzed by aminopeptidase N on CD4+ and CD8+ spleen T cells

Exogenous methionine enkephalin incubated with CD4+ or CD8+ T cells purified from murine spleen is metabolized primarily, if not exclusively, by aminopeptidase N (aminopeptidase M, EC 3.4.11.2), a membrane-anchored ectopeptidase. The enzyme activity is identified by its substrate specificity, sensitivity to inhibition by amastatin, and immunoreactivity with antibody to rat kidney aminopeptidase N. Activation of CD4+ T cells results in a small increase per cell in aminopeptidase N activity.