NOSH-aspirin (NBS-1120) inhibits estrogen receptor negative breast cancer in vitro and in vivo by modulating redox-sensitive signaling pathways.

Estrogen receptor (ER)-negative breast cancers are known to be aggressive and unresponsive to anti-estrogen therapy, and triple negative breast cancers are associated with poor prognosis and metastasis. Thus, new targeted therapies are needed. FOXM1 is abundantly expressed in human cancers and implicated in protecting tumor cells from oxidative stress by reducing the levels of intracellular reactive oxygen species (ROS). Aspirin, a prototypical anti-cancer agent with deleterious side effects, has been modified to release nitric oxide and hydrogen sulfide, called NOSH-aspirin (NOSH-ASA), generating a 'safer' class of new anti-inflammatory agents. We evaluated NOSH-ASA against (ER)-negative breast cancer using cell lines and a xenograft mouse model. NOSH-ASA strongly inhibited growth of MDA-MB-231 and SKBR3 breast cancer cells with low IC50s of 90{plus minus}5 and 82{plus minus}5 nM, respectively, with marginal effects on a normal breast epithelial cell line. NOSH-ASA inhibited cell proliferation, caused G0/G1 phase arrest, increased apoptosis, and was associated with increases in ROS. In MDA-MB-231 cell xenografts, NOSH-ASA reduced tumor size markedly, which was associated with reduced proliferation (decreased PCNA expression), induction of apoptosis (increased TUNEL positive cells), and increased ROS, while NF-kB and FoxM1 that were high in untreated xenografts were significantly reduced. mRNA data for FoxM1, p21 and CyclinD1 corroborated with the respective protein expressions and arrest of cells. Taken together, these molecular events contribute to NOSH-ASA mediated growth inhibition and apoptotic death of (ER)-negative breast cells in vitro and in vivo. Additionally, as a ROS-inducer and FOXM1-inhibitor, NOSH-ASA has potential as a targeted therapy. Significance Statement In this investigation, we examined the cellular effects and xenograft tumor inhibitory potential of NOSH-aspirin, an NO and H2S-donating hybrid, against ER-negative breast cancer, which currently lacks effective therapeutic options. The induction of reactive oxygen species and subsequent downregulation of FOXM1 represents a plausible mechanism contributing to the observed decrease in cell proliferation and concurrent increase in apoptosis. NOSH-ASA demonstrated a remarkable reduction in tumor size by 90% without inducing any observable gross toxicity, underscoring its promising translational potential.

Genome-wide association study on detailed profiles of smoking behavior and nicotine dependence in a twin sample.

Smoking is a major risk factor for several somatic diseases and is also emerging as a causal factor for neuropsychiatric disorders. Genome-wide association (GWA) and candidate gene studies for smoking behavior and nicotine dependence (ND) have disclosed too few predisposing variants to account for the high estimated heritability. Previous large-scale GWA studies have had very limited phenotypic definitions of relevance to smoking-related behavior, which has likely impeded the discovery of genetic effects. We performed GWA analyses on 1114 adult twins ascertained for ever smoking from the population-based Finnish Twin Cohort study. The availability of 17 smoking-related phenotypes allowed us to comprehensively portray the dimensions of smoking behavior, clustered into the domains of smoking initiation, amount smoked and ND. Our results highlight a locus on 16p12.3, with several single-nucleotide polymorphisms (SNPs) in the vicinity of CLEC19A showing association (P<1 × 10(-6)) with smoking quantity. Interestingly, CLEC19A is located close to a previously reported attention-deficit hyperactivity disorder (ADHD) linkage locus and an evident link between ADHD and smoking has been established. Intriguing preliminary association (P<1 × 10(-5)) was detected between DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) ND diagnosis and several SNPs in ERBB4, coding for a Neuregulin receptor, on 2q33. The association between ERBB4 and DSM-IV ND diagnosis was replicated in an independent Australian sample. Recently, a significant increase in ErbB4 and Neuregulin 3 (Nrg3) expression was revealed following chronic nicotine exposure and withdrawal in mice and an association between NRG3 SNPs and smoking cessation success was detected in a clinical trial. ERBB4 has previously been associated with schizophrenia; further, it is located within an established schizophrenia linkage locus and within a linkage locus for a smoker phenotype identified in this sample. In conclusion, we disclose novel tentative evidence for the involvement of ERBB4 in ND, suggesting the involvement of the Neuregulin/ErbB signalling pathway in addictions and providing a plausible link between the high co-morbidity of schizophrenia and ND.

Prevalence of eczema among older persons: A population-based cross-sectional study.

Background There are very few population-based studies on the prevalence of eczema among older persons Aims To estimate the prevalence and types of eczema in those aged 65 years or more in the community and to evaluate the effectiveness of community-based interventions for case finding. Methods In the first stage of this cross-sectional survey, trained health workers of a non-governmental organization surveyed the eligible population and identified persons likely to have eczema. In the second stage, dermatologists examined such persons to ascertain the diagnosis. Statistical analysis was done using Epi Info software version 7. Prevalence of eczema was expressed in percentages. Chi-square test was used for comparing the difference in prevalence of eczema in various age groups and sex. Results Health workers identified 98 persons as possible cases of eczema after interviewing 385 older persons in the community. Among them 95 persons were examined by dermatologists and 44 were confirmed to have eczema (diagnostic accuracy of health workers = 46.3%).Point prevalence of eczema was 11.4% (44/385). Prevalence was similar in males and females. It was greater (18.2 %) among persons aged 81 years or more. Asteatotic eczema, gravitational eczema and lichen simplex chronicus were the more common types of eczema. Limitations: Possible underestimation of the prevalence rates due to limited medical knowledge of health workers; limited facilities for examination and investigations at the medical camps and home visits. Conclusion There appears to be a considerable burden of eczema among older persons in the community. A community-based approach involving non-governmental organizations has the potential to identify cases and offer care close to their homes.

Barriers to Urogynecologic Care for Racial and Ethnic Minority Women: A Qualitative Systematic Review.

IMPORTANCE: Studies have sought to evaluate factors that have perpetuated disparities in health care, including urogynecologic care. However, there remains a lack of understanding of barriers to care specific to racial/ethnic minority populations. OBJECTIVES: We aimed to report identified barriers to urogynecologic care (eg, care for symptoms/diagnoses of urinary incontinence [UI], accidental bowel leakage [ABL], and pelvic organ prolapse [POP]) for underrepresented racial and ethnic minority (URM) women in the United States. STUDY DESIGN: We conducted a systematic search for studies through 5 electronic bibliographic databases. Inclusion criteria for eligible studies included the following: (1) studies reporting barriers to care for those with urogynecologic symptoms/diagnoses, (2) publication date year 2000 or later. Exclusion criteria included study cohorts with children, exclusively non-U.S. populations, cohorts without URM participants, and studies without qualitative research methodology. Study methodology, characteristics, as well as barriers and facilitators to urogynecologic care were captured using a thematic synthesis approach. RESULTS: There were 360 studies identified. Twelve studies met criteria: 6 had study populations with UI, 3 with POP, 2 on UI and/or POP, and 1 on ABL. There were 7 focus group studies (total 44 groups, n = 330), 4 interview studies (total 160 interviews, n = 160), and 1 had both (10 interviews, 6 groups, n = 39). Most studies reported on patient-associated barriers (n = 10/12) and physician/provider-associated barriers (n = 10/12), whereas only half reported system-associated barriers (n = 6/12). CONCLUSION: Identified barriers to urogynecologic care for URM populations were examined. Findings likely do not fully reflect barriers to urogynecologic care for URM populations. Comprehensive evaluation of social determinants of health and systemic racism within studies is needed to understand the unique barriers present for racially/ethnically diverse populations.

Knowledge of Pelvic Floor Dysfunction in African American and Afro-Caribbean Women Seeking Medical Care in a Primary Care Ambulatory Setting.

IMPORTANCE: Approximately one fourth of U.S. community-dwelling women will develop a pelvic floor dysfunction (PFD) within their lifetimes. Prior research has revealed that knowledge of PFD was low to moderate in the general population and lower among Black patients. OBJECTIVE: This study aimed to assess the proficiency of urinary incontinence and pelvic organ prolapse (POP) in self-identified African American and Afro-Caribbean adult (age ≥ 18 years) female patients seeking medical care in our ambulatory setting. STUDY DESIGN: In this cross-sectional study, we administered the Prolapse and Incontinence Knowledge Questionnaire to patients in primary care and gynecology ambulatory settings at an academic medical center in Central Brooklyn. We used a multivariable Poisson regression model to find characteristics of the participants that are associated with proficiency in Prolapse and Incontinence Knowledge Questionnaire domains. RESULTS: A total of 266 survey participants self-identified as African American or Afro-Caribbean. Overall, using a multivariable model, knowledge of POP was significantly higher among African Americans than Afro-Caribbeans, and 75.5% of our patients reported that they would seek information on urinary incontinence and POP from a medical provider (gynecologist or primary care doctor) compared with other alternatives (eg, internet, 19.6%). CONCLUSIONS: These findings highlight subgroups that could benefit from provider-initiated education regarding PFD. Furthermore, although Black patients are often homogenized in research studies, differences may exist within subgroups likely because of varying interplays of structural racism and other social determinants of health, which may serve as an area of future research.

Assessment of the Efficacy of TMJ Arthroscopy-Assisted Masseter Nerve Avulsion on Hemimasticatory Spasm: An Original Research.

The goal of this study is to find a cure for the masticatory muscle disease known as hemimasticatory spasm (HMS). This retrospective investigation intends to find a more efficient therapeutic approach for HMS patients by examining the clinical effectiveness of masseteric nerve avulsion performed on HMS using a temporomandibular arthroscope. A clinical study was piloted where the subjects were treated for masseter nerve avulsion by TMJ arthroscopy. The follow-up was done till 2 years, and the subjects were evaluated for the various characteristics like difficulties, masticatory abilities, and various sounds at the joint for the various functions of the joint. The diagnosis was done using the electrophysiological electromyogram (EMG) at the designated time intervals. There was a complete remission in all the subjects. The masseter nerve avulsion was effective since the scores lowered. Within 3 years of the operation, electrophysiological EMG depicted no discharge potential with a high frequency, and the total efficiency when paired with the clinical effectiveness was deemed acceptable. The maximal masseter power between the treated and nontreated sides was comparable. The mastication, on comparing, was also as effective as the normal side; however, lower mastication was noted in the first year. The avulsed nerve tissues lacked any apparent demyelination. Masseteric nerve avulsion with temporomandibular arthroscope assistance provided acceptable and stable total effectiveness for the intervention of the hemimasticatory spasm. While the strength of the muscle of the afflicted side was only marginally reduced, its masticatory effectiveness was optimally preserved.

Assessment of Pain Management After Orthognathic Surgery by the Administration of Montelukast: An Original Research.

Introduction: Opioid may cause undue risk after surgical procedures like orthognathic surgeries. The present study was aimed to determine how the preoperative administration of oral montelukast affected the degree of postoperative discomfort following bimaxillary orthognathic surgery (BOS). Methodology: This study included all skeletal class III subjects scheduled for BOS. The participants were split into placebo and montelukast groups at random. Every patient received a 10-mL serving of apple juice an hour prior to the surgery; however, for the intervention group, a montelukast 10 mg pill was dissolved in the juice. The same surgical team and general anesthetic guidelines were used for all procedures. The visual analog scale (VAS) was used to calculate postoperative pain at designated intervals. The significance level for the statistical analysis was determined using the Statistical Package for the Social Sciences (SPSS) version 23. Results: The control subjects had a higher level of pain at all the intervals than the intended drug test group. Also, the control group needed more analgesics than the test group. There was one observation made that the length of the surgery had an impact on the postoperative pain. Conclusion: Preoperative montelukast medication may be useful in minimizing postoperative discomfort following bimaxillary orthognathic surgery. More research is required for greater relevance.

Protease inhibitors selectively block T cell receptor-triggered programmed cell death in a murine T cell hybridoma and activated peripheral T cells.

The hypothesis that cytoplasmic proteases play a functional role in programmed cell death was tested by examining the effect of protease inhibitors on the T cell receptor-mediated death of the 2B4 murine T cell hybridoma and activated T cells. The cysteine protease inhibitors trans-epoxysuccininyl-L-leucylamido-(4-guanidino) butane (E-64) and leupeptin, the calpain selective inhibitor acetyl-leucyl-leucyl-normethional, and the serine protease inhibitors diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride, all showed dose-dependent blocking of the 2B4 death response triggered by the T cell receptor complex and by anti-Thy-1. These protease inhibitors enhanced rather than inhibited IL-2 secretion triggered by T cell receptor cross-linking, showing that they did not act by preventing signal transduction. Growth inhibition induced by cross-linking the 2B4 T cell receptor, measured by inhibition of thymidine incorporation, was not generally blocked by these protease inhibitors. All five of these protease inhibitors enhanced rather than blocked 2B4 cell death triggered by dexamethasone, an agent previously shown to have a death pathway antagonistic with that of the TCR. 2B4 cytolysis by the cytotoxic agents staphylococcal alpha-toxin and dodecyl imidazole, and that caused by hypotonic conditions, was not significantly affected by the five protease inhibitors tested. The selected protease inhibitors blocked both the apoptotic nuclear morphology changes and DNA fragmentation induced by T cell receptor cross-linking, and enhanced both these properties induced by dexamethasone in 2B4 cells. The T cell receptor-induced death of activated murine lymph node T cells and human peripheral blood CD4+ T cells was blocked by both cysteine and serine protease inhibitors, showing that the protease-dependent death pathway also operates in these systems.

Different interleukin-1 beta converting enzyme (ICE) family protease requirements for the apoptotic death of T lymphocytes triggered by diverse stimuli.

Two cell permeable peptide fluoromethyl ketone inhibitors of Interleukin-1 beta converting enzyme (ICE) family proteases were tested as inhibitors of apoptotic cell death of T lymphocytes at various stages of differentiation. The CPP-32-like protease activity in apoptotic cell lysates was blocked by both the ICE inhibitor Cbz-Val-Ala-Asp(OMe)-fluoromethyl ketone (ZVAD-FMK) as well as its truncated analog Boc-Asp(OMe)-fluoromethyl ketone (BD-FMK), which failed to block ICE. In vitro apoptotic death in murine thymocytes triggered by the independent agents dexamethasone, etoposide, radiation, anti-Fas, and anti-CD3 was blocked equally well by BD-FMK and ZVAD-FMK, but not by the control reagent Cbz-Phe-Ala-fluoromethyl ketone. In activated T cell blasts, while anti-CD3/ Fas-induced death was almost completely inhibited by both ZVAD-FMK, and BD-FMK, death induced by dexamethasone, etoposide, or irradiation was more sensitive to inhibition by BD-FMK. In the murine T cell line CTLL-2, apoptotic death induced by IL-2 withdrawal, etoposide, or dexamethasone was inhibited by BD-FMK, while ZVAD-FMK was without effect. These data indicate that ICE-family proteases comprise a common functional step in distinct T cell apoptotic death pathways, but suggest that different family members are likely to be critical in various differentiated T cell types, even when triggered by the same stimulus.

T cell receptor (TCR)-induced death of immature CD4+CD8+ thymocytes by two distinct mechanisms differing in their requirement for CD28 costimulation: implications for negative selection in the thymus.

Negative selection is the process by which the developing lymphocyte receptor repertoire rids itself of autoreactive specificities. One mechanism of negative selection in developing T cells is the induction of apoptosis in immature CD4+CD8+ (DP) thymocytes, referred to as clonal deletion. Clonal deletion is necessarily T cell receptor (TCR) specific, but TCR signals alone are not lethal to purified DP thymocytes. Here, we identify two distinct mechanisms by which TCR-specific death of DP thymocytes can be induced. One mechanism requires simultaneous TCR and costimulatory signals initiated by CD28. The other mechanism is initiated by TCR signals in the absence of simultaneous costimulatory signals and is mediated by subsequent interaction with antigen-presenting cells. We propose that these mechanisms represent two distinct clonal deletion strategies that are differentially implemented during development depending on whether immature thymocytes encounter antigen in the thymic cortex or thymic medulla.

Supraoptimal peptide-major histocompatibility complex causes a decrease in bc1-2 levels and allows tumor necrosis factor alpha receptor II-mediated apoptosis of cytotoxic T lymphocytes.

Cytotoxic T lymphocytes (CTLs) are primary mediators of viral clearance, but high viral burden can result in deletion of antigen-specific CTLs. We previously reported a potential mechanism for this deletion: tumor necrosis factor (TNF)-alpha-mediated apoptosis resulting from stimulation with supraoptimal peptide-major histocompatibility complex. Here, we show that although death is mediated by TNF-alpha and its receptor (TNF-RII), surprisingly neither the antigen dose dependence of TNF-alpha production nor that of TNF-RII expression can account for the dose dependence of apoptosis. Rather, a previously unrecognized effect of supraoptimal antigen in markedly decreasing levels of the antiapoptotic protein Bc1-2 was discovered and is likely to account for the gain in susceptibility or competence to sustain the death signal through TNF-RII. This decrease requires a signal through the TCR, not just through TNF-RII. Although death mediated by TNF-RII is not as widely studied as that mediated by TNF-RI, we show here that it is also dependent on proteolytic cleavage by caspases and triggered by a brief initial encounter with antigen. These results suggest that determinant density can regulate the immune response by altering the sensitivity of CTLs to the apoptotic effects of TNF-alpha by decreasing Bc1-2 levels.

Role of antigen, CD8, and cytotoxic T lymphocyte (CTL) avidity in high dose antigen induction of apoptosis of effector CTL.

Experimental data suggest that negative selection of thymocytes can occur as a result of supraoptimal antigenic stimulation. It is unknown, however, whether such mechanisms are at work in mature CD8+ T lymphocytes. Here, we show that CD8+ effector cytotoxic T lymphocytes (CTL) are susceptible to proliferative inhibition by high dose peptide antigen, leading to apoptotic death mediated by TNF-alpha release. Such inhibition is not reflected in the cytolytic potential of the CTL, since concentrations of antigen that are inhibitory for proliferation promote efficient lysis of target cells. Thus, although CTL have committed to the apoptotic pathway, the kinetics of this process are such that CTL function can occur before death of the CTL. The concentration of antigen required for inhibition is a function of the CTL avidity, in that concentrations of antigen capable of completely inhibiting high avidity CTL maximally stimulate low avidity CTL. Importantly, the inhibition can be detected in both activated and resting CTL. Blocking studies demonstrate that the CD8 molecule contributes significantly to the inhibitory signal as the addition of anti-CD8 antibody restores the proliferative response. Thus, our data support the model that mature CD8+ CTL can accommodate an activation signal of restricted intensity, which, if surpassed, results in deletion of that cell.

Dermatitis Artefacta Presenting with Localized Alopecia of Right Eyebrow and Scalp.

Dermatitis artefacta (DA) and trichotemnomania are self-inflicted dermatoses often preceded by psychosocial stressful events. A 38-year-old female presented with sudden loss of hair in the right frontal area along with discoloration and edema of skin. On examination, there was complete loss of hair involving the right frontal area and the lateral half of right eyebrow with skin over that area appearing scalded, edematous, bruised, and discolored. After a detailed medical and psychological evaluation, a clinical diagnosis of DA with trichotemnomania was made. A tactful multidisciplinary approach is essential in managing such patients as outright referral to a psychiatrist could be counterproductive.

VDAC is a conserved element of death pathways in plant and animal systems.

Programmed cell death (PCD) is very much a part of plant life, although the underlying mechanisms are not so well understood as in animals. In animal cells, the voltage-dependent anion channel (VDAC), a major mitochondrial outer membrane transporter, plays an important role in apoptosis by participating in the release of intermembrane space proteins. To characterize plant PCD pathways by investigating the function of putative components in a mammalian apoptotic context, we have overexpressed a rice VDAC (osVDAC4) in the Jurkat T-cell line. Overexpression of osVDAC4 induces apoptosis, which can be blocked by Bcl-2 and the VDAC inhibitor DIDS. Modifying endogenous VDAC function by DIDS and hexokinase II (HxKII) in Jurkat cells inhibits mitochondria-mediated apoptotic pathways. Finally, we show that DIDS also abrogates heat-induced PCD in cucumber cotyledons. Our data suggest that VDAC is a conserved mitochondrial element of the death machinery in both plant and animal cells.

Reactive oxygen species regulate quiescent T-cell apoptosis via the BH3-only proapoptotic protein BIM.

The survival of quiescent T cells in the peripheral immune system is dependent on signals transmitted from the extracellular environment. The requirement for survival factors is also manifested in vitro, providing a robust system to examine molecular mechanisms underlying T-cell death. We show that peripheral T cells cultured in the absence of survival factors accumulate reactive oxygen species (ROS), upregulate BIM (Bcl-2-interacting mediator of death) and inducible nitric oxide synthase (iNOS) expression, culminating in Fas-independent neglect-induced death (NID). We have examined ROS, iNOS and cytokine modulation of T-cell NID. Antioxidants inhibit BIM induction, caspase activation and apoptosis but do not promote cell cycle entry. iNOS-deficient T cells are protected from apoptosis, implicating iNOS in the regulation of NID via suppression of Bcl-x(L) expression and consequent inhibition of BIM activity. Finally, we show that the prosurvival cytokine IL-7 elevates Bcl-x(L) expression and transcriptionally regulates iNOS but not BIM expression in T cells.

Apoptotic cell death and cytokine dysregulation in human immunodeficiency virus infection: pivotal factors in disease progression.

The progressive loss of CD4 T lymphocyte is patognomonic of Human Immunodeficiency Virus (HIV) infection and results in immunodeficiency and the appearance of acquired immunodeficiency syndrome (AIDS)-defining pathologies. Although a percentage of CD4 T lymphocytes is destroyed directly by HIV infection, a much higher proportion of lymphocytes remains uninfected and therefore must be destroyed by mechanisms not directly involving viral infection. One such mechanism is apoptotic T cell death (ATCD). ATCD in HIV infection has been shown to be: 1) secondary to cross-linking of CD4 by viral proteins; 2) mediated by both APO-1/Fas and lymphotoxin (LT); and 3) differentially modulated by type 1 and type 2 cytokines. We will briefly analyze the experimental evidences suggesting that ATCD contributes significantly to the immunopathogenesis of HIV/AIDS via depletion of CD4+ T cells.

Antigen-stimulated apoptotic T-cell death in HIV infection is selective for CD4+ T cells, modulated by cytokines and effected by lymphotoxin.

OBJECTIVE: To characterize the mechanism of in vitro antigen-induced apoptotic T-cell death in the peripheral blood mononuclear cells (PBMC) of HIV-1-infected individuals. DESIGN AND METHODS: PBMC from HIV-1 infected and uninfected individuals were unstimulated or stimulated with HIV-1 envelope synthetic peptides (Env) or influenza A virus to determine the extent of antigen-stimulated apoptotic T-cell death, whether this death was limited to the CD4+ subset, and the effects of cytokines on T-cell death. Death was assessed by apoptotic nuclear morphology after 7 days of culture by fluorescence microscopy using a DNA-specific dye. Transwell cultures and supernatant transfers were utilized to test whether a soluble factor produced by HIV-positive PBMC induced death of HIV-negative T cells. Exogenous cytokines [interleukin (IL)-12, interferon (IFN)-gamma, IL-4 and IL-10], as well as antibodies against endogenously produced cytokines (IL-4, IL-10, IL-12, and lymphotoxin) were tested for their ability to modulate death. RESULTS: Antigenic stimulation induced death in PBMC from HIV-positive donors, but not in PBMC from HIV-negative donors. Antigen-stimulated death was seen in CD4+ but not CD8+ T-cell subset from the HIV-positive patients. Apoptotic death was blocked by IL-12, IFN-gamma, anti-IL-4, anti-IL-10, and anti-lymphotoxin, but not by anti-IL-12. Transwell and supernatant transfer experiment indicated that antigen-stimulated HIV-positive PBMC produced a factor that killed T-cell blasts. The factor was inhibited by anti-lymphotoxin, but not by anti-IL-10. CONCLUSIONS: Stimulation of HIV-positive PBMC with CD4-dependent antigens results in selective death of CD4+ T cells that is modulated by cytokines. Our results suggest that apoptotic death is not limited to HIV-infected or HIV-specific T cells, but occurs in bystander cells. Lymphotoxin is a mediator of antigen-stimulated T-cell death in this in vitro model.

Necessity for interaction between adherent and non-adherent rat spleen cells for the generation of a suppressor factor of NK activation.

Whole rat spleen cell populations in culture release constitutively a factor which suppresses the NK activation in response to interleukin-2. Culture supernatants derived from adherent (AD) and non-adherent (NAD) cell preparations obtained from rat spleen cells, did not have a suppressor activity comparable to that present in the culture supernatants of whole spleen cells. When reconstituted mixtures of the AD and NAD cells were cultured, high levels of suppressor activity could again be demonstrated in the culture supernatants, indicating that some kind of co-operation between AD and NAD cells was needed for efficient generation of the suppressor. Non-suppressive culture supernatants derived from NAD cells became suppressive when AD cells were cultured in them. On the other hand, relatively little suppressor activity was generated when NAD cells were cultured in non-suppressive culture supernatants from AD cells. Our results seem to indicate that NAD cells may release some agent which is not itself a suppressor but either (a) induces the generation of suppressor activity from AD cells, or (b) is "processed" into a suppressor agent by AD cells.

MHC class I up-regulation protects some but not all targets against LAK-mediated lysis: possible implications for the existence of LAK cell subpopulations using different recognition strategies.

The effect of gamma-interferon (gamma-IFN) was examined on the lymphokine-activated killer (LAK) cell susceptibility and the levels of major histocompatibility complex (MHC) class I antigen expression on YAC, P815 and EL4 cells. IFN induced a marked increase in the MHC class I antigen expression on all target cells, a concomitant decrease in LAK sensitivity was observed for YAC and P815 cells but not for EL4 cells. In competition experiments, lysis of YAC cells by LAK cells was inhibited by control or IFN-treated YAC and P815 cells, but not by control or IFN-treated EL4 cells. Moreover, lysis of EL4 cells was not inhibited by control or IFN-treated YAC cells. Our results suggest that the effectors killing EL4 are distinct from those killing YAC and/or P815 and that the former are not influenced by the levels of MHC class I antigens on target cells.