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J H Dean

Publications and source records attributed to J H Dean.

At least 19 recordsLinked to original sources
PubMed2001

ICCVAM evaluation of the murine local lymph node assay. Conclusions and recommendations of an independent scientific peer review panel.

The validation status of the murine local lymph node assay (LLNA), a method for assessing the allergic contact dermatitis potential of chemicals, was evaluated by an independent peer review panel (Panel) convened by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM). The LLNA measures lymphocyte proliferation using incorporation of radioactive thymidine or iododeoxyuridine into cells of the draining lymph nodes of mice topically exposed to a test article. The Panel concluded that the assay performed as well as currently accepted guinea pig methods [guinea pig maximization test (GPMT)/Buehler assay (BA)] for the hazard identification of strong to moderate chemical sensitizing agents, but that it might not correctly identify all weak sensitizers or metals (potential false negative response) or all strong irritants (potential false positive response). The Panel concluded also that the LLNA involves less pain and distress than conventional guinea pig methods. The Panel unanimously recommended the LLNA as a stand-alone alternative for contact sensitization hazard assessment, provided that certain protocol modifications were made. These included collection of individual, rather than pooled, animal response data; the inclusion of a concurrent positive control; and consideration of dose-response information and statistical analyses. A standardized LLNA protocol is provided.

Animals↗
PubMed1998

Immunotoxicology assessment in the pharmaceutical industry.

Through several inter-laboratory evaluation studies, selected methods were optimized and evaluated using reference compounds in rodents, to determine their predictive value for detecting toxicity to the immune system. These provide the basis for the OECD, EPA and pending FDA Guidelines. To describe the status of immunotoxicity evaluation using these methods in the pharmaceutical industry, a survey was conducted, and is reported, of ongoing activities among the major pharmaceutical companies. The results describe which assays are performed, how compounds are selected for evaluation; and when, during the drug development process, an evaluation is performed. Finally, the strategy at Sanofi, for the evaluation and application of immunotoxicity methods during the preclinical development of new molecular entities (NMEs) is described. During the past 8 years, Sanofi has evaluated more than 27 NMEs from multiple therapeutic classes as well as four reference compounds (azathioprine, dexamethasone, cyclophosphamide and cyclosporin A). Our experience with multiple animal species (rat, dog and monkey) and immunotoxicity assays selected from the recommended tiers as well as the outcome from the evaluation of our NMEs and reference standards, is described. This experience has led us to believe that immunotoxicology parameters represent an important adjunct for the safety assessment of NMEs. In addition, these methods were easily integrated into the drug development process and yielded an unexpectedly low frequency of positive results. In summary, immunotoxicity can be evaluated on a case-by-case basis driven by pathology or clinical hematology findings, by the drug's indication, the chemical class or indication of the NME evaluated (for example, anti-viral agents), or systematically performed.

Animals↗
PubMed1997

Issues with introducing new immunotoxicology methods into the safety assessment of pharmaceuticals.

Unfortunately, the principal routine toxicology methods employed for the safety assessment of new products are over 40 years old and rely primarily on histopathological evaluation. It is difficult to introduce newer immunotoxicology or molecular toxicology methods into toxicity assessment without extensive and time consuming validation requiring several years due to concern for standardization of methods, inter-laboratory replication of these methods and resistance to acceptance of new methods by both regulatory agencies and industry. During the past 15 years, significant progress has occurred in the fields of molecular biology and basic/clinical immunology which promoted the establishment of newer more sensitive methods to assess cell injury or immune system effects in humans and laboratory animals. This brings us to the challenges associated with trying to introduce new immunotoxicology or molecular toxicology methods into the safety assessment of new products. Our experience at Sanofi Research with immunotoxicity methods development or validation and approaches for molecular toxicology and their application to the preclinical development of new chemical drug entities (NCE) will be discussed. Laboratories to investigate immunotoxicity and molecular toxicology were established during the past 10 years among several industrial research groups for the evaluation of new chemicals and drug candidates. Immunotoxicology methods have been selected and optimized for rodent testing leading to four inter-laboratory collaborative studies to demonstrate the reproducibility and value of these methods for predicting toxicity. Our experience at Sanofi has led us to believe that these newer methods can represent an important part of drug development, should be applied on an as needed basis, and should be driven by data suggestive of an immune or molecular toxicology effect or by the class of the chemical being evaluated. Ex vivo and in vitro assays are selected from a menu of validated methods for application on a case-by-case basis. Results in this area with inter-laboratory validation of these methods will be discussed. Newer molecular toxicology and immunotoxicity methods are beginning to play a more important role in the safety evaluation and risk assessment process.

Animals↗
PubMed1996

The impact of prenatal diagnosis on NTD surveillance.

Active and passive surveillance methods were utilized in an attempt to identify all neural tube defect (NTD)-affected pregnancies in South Carolina, a state previously identified to have a high prevalence of these defects (Greenberg et al., 1983). Sources of case ascertainment included maternal serum alpha-fetoprotein (MSAFP) programmes, prenatal diagnosis (amniocentesis) programmes, physician offices, perinatal centres, hospital medical record departments, and vital records. One hundred and nine NTD cases were identified over 24 months, indicating a prevalence of 1.60 cases per 1000 recorded births and fetal deaths (surveillance 1 October 1992-30 September 1994). Fifty-three (49 per cent) of the 109 NTD-affected pregnancies were either spontaneously or electively aborted prior to 26 weeks' gestation. Only three (6 per cent) of these early termination NTD cases were recorded in vital records, while medical records recorded 40 cases (75 per cent). By monitoring MSAFP programmes and maintaining frequent contact with physician offices and perinatal centres, 85 per cent of these early termination NTD-affected pregnancies were identified. However, for complete ascertainment of NTD-affected pregnancies, the utilization of all of these ascertainment methods was necessary, as each ascertainment method identified NTD cases missed by the other methods. Consideration of the significant impact of prenatal diagnosis on NTD surveillance and the use of multiple ascertainment methods in an attempt at complete ascertainment is particularly important now because of the recent recommendation for the periconceptional use of folic acid to prevent neural tube defects and the need for epidemiological studies to monitor the effectiveness of this prevention.

Abortion, Induced↗
PubMed1995

Surveillance for anencephaly and spina bifida and the impact of prenatal diagnosis--United States, 1985-1994.

PROBLEM/CONDITION: The reported prevalence of anencephaly and spina bifida in the United States has steadily declined since the late 1960s. During this time, the ability to diagnose these defects prenatally has progressed rapidly. Many U.S. birth defects surveillance systems ascertain defects only among live-born infants or among infants and fetuses beyond a certain gestational age, thus excluding defects among pregnancies prenatally diagnosed as being affected by a neural tube defect (NTD) and electively terminated before the gestational age limit. The impact of prenatal diagnosis and subsequent pregnancy termination on the reported prevalence of anencephaly and spina bifida in the United States has not been well established. However, assessment of this impact is crucial to the use of surveillance data to monitor trends in the occurrence of NTDs and the effectiveness of interventions for these defects (e.g., increased consumption of folic acid). REPORTING PERIOD: This report presents data from birth defects surveillance systems in six states over different time periods: Arkansas, 1985-1989; California, 1989-1991; Georgia, 1990-1991; Hawaii, 1988-1994; Iowa, 1985-1990; and South Carolina, 1992-1993. DESCRIPTION OF SYSTEMS: Population-based data about a) live-born and stillborn infants with anencephaly and spina bifida and b) pregnancies electively terminated after prenatal diagnosis of these defects were analyzed from the Arkansas Reproductive Health Monitoring System; the California Birth Defects Monitoring Program; CDC's Metropolitan Atlanta Congenital Defects Program; the Iowa Birth Defects Registry, the University of Iowa, and the Iowa Department of Public Health; and the Greenwood Genetic Center in South Carolina. Data also were analyzed from the Hawaii Birth Defects Monitoring Program, which includes data for some women who were not residents of the state. The systems differed in the size and racial/ethnic composition of the populations studied, the surveillance methods used, the completeness of ascertainment, and the availability and utilization of prenatal testing and pregnancy termination. RESULTS AND INTERPRETATION: Among all pregnancies ascertained in which the infant or fetus had anencephaly or spina bifida, the percentages that were electively terminated ranged from 9% in Arkansas to 42% in Atlanta and Hawaii, with a corresponding increase in the adjusted prevalence of these defects compared with the prevalence at birth. In each system, pregnancies associated with anencephaly were terminated more frequently than were those associated with spina bifida. These data indicate that the impact of prenatal diagnosis and subsequent pregnancy termination on the prevalence at birth of anencephaly and spina bifida differs among geographic areas and populations. Comprehensive surveillance for these defects requires inclusion of pregnancies that are prenatally diagnosed and then terminated. ACTIONS TAKEN: CDC will use these data to promote the inclusion of prenatally diagnosed and terminated pregnancies in estimates of the prevalence of anencephaly and spina bifida generated by birth defects surveillance programs in the United States. Including such pregnancies is crucial to the ability of these programs to monitor trends accurately and to establish the effectiveness of interventions, including the use of folic acid, for these defects.

Abortion, Induced↗
PubMed1993

The integration of investigative toxicology in the drug discovery process.

Integrating toxicology early in the drug discovery process adds value by providing the earliest possible identification of a compound's potential for toxicological and pathological effects relevant to intended clinical use. With this approach true 'lead' candidates, with a high probability of clinical success, are identified and advanced while reducing effort and resources expended on compounds without the requisite therapeutic index. Resources are focussed on the speed of getting a discovery 'lead' into early clinical development, defining the mechanisms of observed preclinical toxicity and their relevance to human use, and developing early safety data with in vitro test systems ahead of in vivo systems where possible, thus reducing animal use.

Animals↗
PubMed1993

Clinical pathologic alterations associated with subcutaneous administration of recombinant human interleukin-4 to cynomolgus monkeys.

Recombinant human interleukin 4 (rhuIL-4) is a candidate for the treatment of refractory cancer based on its potential to enhance immune function. Recombinant human IL-4 was administered subcutaneously at 0, 1, 5, or 25 micrograms/kg/day for 28 days with a 14-day recovery to male and female cynomolgus monkeys as part of the preclinical safety evaluation. Clinical pathologic changes related to treatment with rhuIL-4 were evidence of consumptive coagulopathy, erythrocyte fragmentation, lymphocytosis, and lymphocyte morphologic changes indicative of marked antigenic or mitogenic stimulation, mild eosinophilia and neutrophilia, hypoalbuminemia, hypocholesterolemia, and hypertriglyceridemia. Based on data obtained after the 14-day recovery period, the clinical pathologic changes associated with rhuIL-4 administration were considered to be reversible.

Animals↗
PubMed1992

Pre-clinical toxicity of IL-4: a model for studying protein therapeutics.

The purpose of this presentation was to review issues and findings in the pre-clinical development and evaluation of recombinant human protein therapeutics. Since human cytokines and lymphokines are endogenous proteins, their pre-clinical development and evaluation would seem straightforward and their toxicities minimal. Unfortunately, the pre-clinical development of this class of agents has been problematic and confounding. Some of the clinical toxicities and pharmacodynamics have been predicted by the pre-clinical evaluation and others have not. Some molecules are species specific which limits species selection for pre-clinical evaluation. Other confounding issues include: route of exposure, synergy of toxicity with other lymphokines, length of study design, immunogenicity, predictiveness of pre-clinical evaluation and iatrogenic toxicities. An approach used by SWPRD in the evaluation of this class of molecules was discussed. Insight gained during the pre-clinical and clinical development of these molecules should simplify the further development of protein therapeutics that follow. Specific studies with recombinant human interleukin-4 (rhuIL-4) were reviewed in detail as part of a pre-clinical safety evaluation. Native IL-4 has properties that exemplify many of the immune recognition-induced lymphokines and is produced principally by activated T-lymphocytes CD4+. It is a co-factor in B-cell proliferation and enhances ex vivo B-cell expansion and is believed to be a candidate for the treatment of refractory cancer based on this immune enhancement ability. rhuIL-4 is a 15,400 molecular weight cytokine produced in a yeast expression system.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Subchronic oral and intravenous (i.v.) safety evaluation and pharmacokinetics in rats and dogs of ipazilide fumarate (Win 54, 177-4), an antiarrhythmic agent.

Ipazilide fumarate (Win 54, 177-4) is a chemically novel antiarrhythmic agent that prolongs ventricular refractoriness and possesses antiectopic activity. Subchronic (29 days) nonclinical safety evaluation of ipazilide was conducted following oral and iv administration in Sprague-Dawley rats (20-320 mg/kg oral and 1.25-10 mg/kg iv) and 14 and 28 days in beagle dogs (3-30 mg/kg oral and 2.5-20 mg/kg iv). The pharmacokinetic parameters of ipazilide indicate that ipazilide is absorbed (tmax less than or equal to 1 hr) in fasted rats and dogs following single and repeated oral administrations. The apparent elimination half-life in the two species is approximately 1 hr (except in rats at a dosage of 320 mg/kg), suggesting rapid clearance. Increases in liver weights (rats 320 mg/kg) accompanied by the observation of centrilobular hypertrophy of hepatocytes were considered an expression of an adaptive metabolic response of the liver to ipazilide and may be associated with the induction of microsomal enzymes. Duodenal villous atrophy and epithelial hyperplasia (rats, 80 and 320 mg/kg) were interpreted to represent an irritant response to the drug. Local irritation was also observed at the injection site in rats and dogs. Dogs tolerated the oral and the iv administration of ipazilide at dosages of up to 30 and 20 mg/kg, respectively. Despite emesis (oral dogs), which was reduced in frequency following repeated treatment over several weeks, plasma levels in treated dogs (i.e., Cmax 4-5 micrograms/ml) were approximately twice that required to convert spontaneous arrhythmias in the conscious dog model 24 hr after myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Preclinical evaluation of recombinant human interleukin-4.

Recombinant human IL-4 (rhuIL-4) is primate-specific and produces multiple biologic effects on lymphoid cells involved in protection against cancer. RhuIL-4 was evaluated in the cynomolgus monkey to support clinical studies for the immunotherapy of cancer. Administration of rhuIL-4 to monkeys by SC injection of 0, 0.5, 2.5 or 12.5 micrograms/kg BID for one-month (with two-week recovery) resulted in alterations in clinical chemistry and hematology (CCH) parameters consistent with a consumptive coagulopathy. Histomorphologic evaluation revealed increased granulopoiesis, testicular atrophy, and proliferative and inflammatory vascular lesions (VL). IVL principally affected the arterial tree with some proliferation of medial smooth muscle. During the latter part of the treatment and recovery period. CCH parameters approached or returned to pretreatment values, the former finding attributed to the production of antibody to rhuIL-4. At final necropsy, bone marrow appeared normal, and IVL decreased in incidence and severity. ELISA studies of serum indicated 50-90% of the monkeys developed antibody titers > 1000 by Day 22 (not observed in man). The frequency and severity of adverse effects due to rhuIL-4 in the clinic appear to be does-related and reversible with few objective responses to therapy observed. Common toxicities included milk to moderated fever and fatigue and an occasional change in hematopoietic, hepatic and renal function. The monkey predicted hematologic findings, but not all target organ effects.

Animals↗
PubMed1992

Correlation between chemical suppression of natural killer cell activity in mice and susceptibility to cytomegalovirus: rationale for applying murine cytomegalovirus as a host resistance model and for interpreting immunotoxicity testing in terms of risk of disease.

The purpose of this study was to determine the relationship between chemical suppression of natural killer (NK) cell activity in mice and chemical effects on susceptibility to murine cytomegalovirus (MCMV) infection. The goal was to provide a rational basis for applying MCMV as a host resistance model for immunotoxicity testing and to provide risk assessors some guidance in relating suppression of NK cell activity to enhanced risk of disease. Data from studies with eight chemicals administered in various doses and by various routes were evaluated, and a significant correlation was observed between chemical suppression of virus-augmented NK cell activity and increased mortality due to MCMV infection. In contrast, effects of the same chemical treatments on spontaneous NK cell activity (i.e., basal activity in uninfected mice) did not correlate with effects of these chemicals on mortality due to MCMV. Although chemicals that suppressed spontaneous NK cell activity enhanced infection, the converse was not always true--that is, increased susceptibility to infection and suppression of virus-augmented NK cell activity were observed on three occasions when spontaneous NK cell activity was unaffected. This latter phenomenon plus the fact that for two chemicals spontaneous NK was suppressed at concentrations twofold below that which affected mortality appear to account for the poor statistical correlation. Nevertheless, the data indicate that MCMV is a useful host resistance model to be applied in immunotoxicity testing when suppression of NK cell activity has been demonstrated. However, virus-augmented activity may be a better indicator than spontaneous activity. The data also indicated that suppression of NK cell activity is predictive of increased susceptibility to infection and hence provides qualitative guidance (hazard identification) to risk assessors.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Examination of immune parameters and host resistance mechanisms in B6C3F1 mice following adult exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Adult female B6C3F1 mice were given a single ip dose of 0, 01, 1.0, or 10.0 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and examined for immune function and host resistance 7-10 d later. Exposure to TCDD resulted in a significant dose-related decrease in induction of both IgM and IgG antibody-forming cells. This suppression was noted for both T-dependent and T-independent antigens. TCDD at a dosage of 10 micrograms/kg was shown to suppress production of antibody to viral hemagglutinin. In contrast, TCDD exposure had no significant effect on natural killer cell function, production of interferon, or various parameters of macrophage function. Assessment of host resistance revealed a significant increase in susceptibility to fatal infection with influenza virus, but no significant alteration in susceptibility to infection with the bacterium Listeria monocytogenes.

Animals↗
PubMed1989

Functional and biochemical disposition of 7,12-dimethylbenz[a]anthracene in murine lymphoid cells.

The metabolism of the polycyclic aromatic hydrocarbon (PAH) 7,12-dimethylbenz[a]anthracene (DMBA) was studied in murine lymphocytes. This carcinogen has previously been shown to be immunosuppressive to lymphocytes regardless of their ability to be induced via the Ah locus and receptor. Experiments were designed to quantify the generation of metabolites of DMBA by lymphocytes incubated with [14C]DMBA and to ascertain whether radioactivity was covalently bound to cellular macromolecules in DMBA-exposed lymphocytes. No significant metabolism of DMBA was detected in culture supernatants, except when cultures were incubated in the presence of Arochlor-induced rat liver 9000 x g supernatants (S9). Covalent binding of 14C to cellular macromolecules was enhanced approximately eightfold in the presence of S9. Inhibition of monooxygenase activity by alpha-naphthoflavone did not modulate the immunosuppressive character of DMBA. Furthermore, addition of S9 did not amplify or ablate DMBA-mediated suppression of lymphocyte proliferation to the mitogen concanavalin A (Con A). Selected metabolites of DMBA were evaluated for immunosuppressive effects in cultures stimulated with mitogens and cellular alloantigens. 7-Hydroxymethyl-12-methylbenz[a]anthracene (OHMe) and 5,6-dihydro-5,6-dihydroxybenz[a]anthracene (Diol) were found to cause only slightly greater suppression of lymphocyte responses than DMBA. Thus, it appears that metabolites of DMBA were not responsible for the immunosuppression observed in lymphocyte cultures and that lymphocytes were not equipped to metabolize any significant amount of DMBA. These data lend support to the hypothesis that parent compound alone is responsible for the immunosuppressive effects observed in murine lymphocyte culture.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Suppression of murine cytotoxic T-lymphocyte induction following exposure to 7,12-dimethylbenz[A]anthracene: dysfunction of antigen recognition.

Exposure of murine lymphocytes to the carcinogenic polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene (DMBA) results in significant suppression of a variety of immunological parameters, including the induction of cytotoxic T-lymphocytes (CTL). This CTL suppression may be reversed in vitro by the addition of exogenous cellular activation products, including IL-2. The current study demonstrated that DMBA-induced CTL suppression occurs throughout the induction process, with the most pronounced effect occurring within 24-48 h of initiation. IL-2-mediated restoration of suppression is effective only within this critical window. These findings suggest an effect by DMBA on both the T-helper (Th) and CTL-precursor (CTLp) subsets. Alloantigen-specific CTL generated from murine thymocytes in the presence of DMBA and Th-derived factors (thus circumventing the Th) displayed an almost identical degree of CTL suppression to that of splenocytes, indicating a direct effect of DMBA on the CTLp. Antigen nonspecific, polyclonal CTL activation by the lectin leucoagglutinin or by IL-2 (LAK cells) was unaffected by chemical exposure, indicating that DMBA preferentially affects antigen-specific activation rather than the cytolytic process itself. Conversely, polyclonal CTL induced with monoclonal antibodies directed against the T-cell receptor-associated subunit CD3, in the presence of conditioned medium, was suppressed in a manner similar to antigen-mediated CTL. The CD3 receptor subunit acts as a transmembrane activation signal following binding of antigen to the specific receptor, further implicating dysfunction of antigen recognition or signal processing following DMBA exposure. This was confirmed by the observation that DMBA exposure prevents the anamnestic response of CTL memory cells following re-exposure to eliciting tumor antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Target cell specificity of immunosuppression in murine lymphocytes exposed to 1,4-bis[(2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD).

Exposure of murine lymphocytes to the highly-substituted anthraquinone 1,4-bis[(2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD) results in a profound suppression of cytotoxic T-lymphocyte function. This immunosuppression is confined to CTL induction and cannot be restored by addition of exogenous interleukin-2 (IL-2), suggesting a defect at the level of the cytotoxic T-lymphocyte precursor (CTLp) cell. Production of both IL-1 and IL-2 were normal, and responsiveness to IL-1 was unaltered, although lymphocytes displayed a reduced responsiveness to IL-2. Cell surface marker analysis demonstrated no changes in relative numbers of lymphoid cell subsets, implying functional rather than population changes. The ability to activate CTLp with lectins was markedly reduced, as was CTL induction in thymocytes lacking functional T-helper cells. These data suggest that CTL suppression following in vivo or in vitro exposure to AEAD is due primarily to a direct effect on the CTLp cell.

Animals↗
PubMed1989

Selective immunosuppression following exposure to a novel anthraquinone, 1,4-bis[(2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD).

The immune response of murine splenic lymphocytes was characterized following both in vivo and in vitro exposure to the novel and highly-substituted anthraquinone AEAD. Gross indicators of toxicity such as changes in body weight, lymphoid organ weights or lymphoid organ cellularity were unaffected. Similarly, the antibody plaque-forming cell response and natural killer cell function were unaltered. The most consistent effect noted was the selective suppression of the cytotoxic T-lymphocyte (CTL) response, which persisted for an extended period of time following in vivo exposure at concentrations of 0.75-3.0 micrograms/g. In contrast to the CTL suppression induced by the polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]-anthracene, AEAD-induced CTL suppression could not be restored by addition of exogenous interleukin-2. Studies are currently underway to further characterize AEAD-induced immunosuppression at the cellular and molecular levels.

Animals↗
PubMed1989

Suppression of cytolytic function in murine lymphocytes exposed to 1,4-bis[(2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD): inhibition of proliferation by cytotoxic T-lymphocyte precursors.

Previous reports have shown that exposure of murine splenic lymphocytes to the substituted anthraquinone 1,4-bis[(2-aminoethyl)amino]-5,8-dihydroxy-9,10-anthracenedione dihydrochloride (AEAD) results in a persistent, strong immunosuppression which is limited to induction of cytotoxic T-lymphocytes (CTL). In the present study the cellular mechanism of this specificity was examined in detail. Proliferation of T-lymphocytes is inhibited by in vitro exposure to AEAD, with suggestive evidence that this inhibition may be selective for the CTL precursor cells. Activation and differentiation of CTL precursors into functional CTL, as well as the function of T-helper lymphocytes, was unaffected by AEAD exposure. Rather, the committed CTL precursor cells are prevented from clonal proliferation, resulting in a much smaller population of antigen-induced CTL effectors. Finally, it was shown that AEAD is unable to prevent the anamnestic response of CTL memory cells to eliciting antigen. Taken together these data provide strong evidence that AEAD-induced CTL suppression results from its antiproliferative effect, directed primarily toward the CTL precursor subpopulation. This effect is manifested as decreased CTL function due to lower absolute number of specific CTL, since AEAD has no significant direct effect on expression of either specific or polyclonal cytolysis by T-lymphocytes.

Animals↗