Regulation of the immune response by subclasses of T lymphocytes. II. The effect of adult thymectomy upon humoral and cellular responses in mice

INFLA score: a novel inflammatory marker for assessing cardiometabolic disease risk in obese individuals

BACKGROUND

The low-grade inflammation score (INFLA-score) is a composite index that assesses chronic inflammatory status using multiple inflammatory markers. However, its correlation with cardiometabolic diseases (CMDs) in obese populations remains unclear.

METHODS

We conducted a prospective cohort study involving 79,160 participants with obesity (BMI ≥ 30 kg/m2) from the UK Biobank. The INFLA-score was calculated based on high-sensitivity C-reactive protein, leukocyte count, platelet count and granulocyte/lymphocyte ratio. We employed Kaplan-Meier survival curves, multivariable Cox regression, restricted cubic splines and accelerated time-to-failure models to analyse the association between the INFLA-score and CMDs risk, including coronary heart disease (CAD), stroke and type 2 diabetes mellitus (T2DM).

RESULTS

Over a median follow-up of 161.41 months, we recorded 14,903 CMDs events, comprising 7184 CAD cases, 1914 strokes and 7924 T2DM cases. Cox regression analysis revealed that each unit increase in the INFLA-score corresponded to a 1.5%, 1.1%, 1.2% and 2.4% increase CMDs risk (HR: 1.015, 95% CI 1.013-1.018), CAD risk (HR: 1.011, 95% CI 1.007-1.015), stroke risk (HR: 1.012, 95% CI 1.004-1.020) and T2DM risk (HR: 1.024, 95% CI 1.020-1.028), respectively. Restricted cubic spline analysis indicated a non-linear relationship between cumulative INFLA-score and CMDs risk (P = 0.044). Subgroup analysis revealed interactions between sex, age, history of lipid-lowering drug use, and INFLA-score regarding CMDs risk. Sensitivity analysis corroborated the main findings.

CONCLUSION

Our findings strongly support the close association between INFLA-score and CMDs risk, particularly notable in women, those aged < 55, and individuals with a history of lipid-lowering drug use. These findings offer new insights into the role of inflammation in obesity-related CMDs, suggesting potential applications for prevention and identification of high-risk populations.

The neutrophil-to-lymphocyte ratio is associated with coronary heart disease risk in adults: A population-based study

The purpose of this study was to look at any connections that could exist between neutrophil-lymphocyte ratio and coronary heart disease. We performed a cross-sectional research of 13732 participants in the National Health and Nutrition Examination Survey who were 40 or older. Multivariate logistic regression models investigated the relationship between neutrophil-to-lymphocyte ratio levels and coronary heart disease risk. To investigate potential nonlinear connections, smoothed curve fitting was used. When a nonlinear relationship was discovered, the inflexion point was determined using a recursive method. After controlling for relevant confounders, neutrophil-to-lymphocyte ratio was independently linked to a higher risk of coronary heart disease (OR = 1.74, 95% CI:1.30-2.33, P = 0.0002). Subgroup analyses showed statistically significant positive associations between neutrophil-to-lymphocyte ratio and coronary heart disease risk in women (OR = 1.25, 95% CI:1.09-1.43), participants 60 years of age and older (OR = 1.09, 95% CI:1.00-1.19), smoking status for every day or not at all (OR = 1.23, 95% CI:1.00-1.52; OR = 1.09, 95% CI:1.00-1.19), alcohol use status for moderate alcohol use (OR = 1.11, 95% CI:1.00-1.22), body mass index >30 kg/m2 (OR = 1.42, 95% CI:1.10-1.82), hypertensive (OR = 1.11, 95% CI:1.02-1.22), and individuals without diabetes (OR = 1.17, 95% CI:1.06-1.31). A positive correlation between neutrophil-to-lymphocyte ratio levels and coronary heart disease risk was also seen by smoothing curve fitting, with an inflexion point of 1.08 that was statistically significant (P<0.05). Our research shows elevated neutrophil-to-lymphocyte ratio levels are linked to a higher risk of coronary heart disease.

Clinical and Laboratory Predictors of Long-Term Outcomes after Catheter Ablation for a Ventricular Electrical Storm

Background

Ventricular electrical storm (VES) is characterized by the occurrence of multiple episodes of sustained ventricular arrhythmias (VA) over a short period of time. Radiofrequency ablation (RFA) has been reported as an effective treatment in patients with ventricular tachycardia (VT).

Objective

The aim of the present study was to indicate the short-term and long-term predictors of recurrent VA after RFA was performed due to VES.

Methods

A retrospective, single-centre study included patients, who had undergone RFA due to VT between 2012 and 2021. In terms of the short-term (at the end of RFA) effectiveness of RFA, the following scenarios were distinguished: complete success: inability to induce any VT; partial success: absence of clinical VT; failure: inducible clinical VT. In terms of the long-term (12 months) effectiveness of RFA, the following scenarios were distinguished: effective ablation: no recurrence of any VT; partially successful ablation: VT recurrence; ineffective ablation: VES recurrence.

Results

The study included 62 patients. Complete short-term RFA success was obtained in 77.4% of patients. The estimated cumulative VT-free survival and VES-free survival were, respectively, 28% and 33% at the 12-month follow-up. Ischemic cardiomyopathy and complete short-term RFA success were predictors of long-term RFA efficacy. Neutrophil to lymphocyte ratio (NLR) and GFR <60 mL/min/1.73 m2 were associated with VES recurrence. NLR ≥2.95 predicted VT and/or VES recurrence with a sensitivity of 66.7% and specificity of 72.2%.

Conclusion

Ischemic cardiomyopathy and short-term complete success of RFA were predictors of no VES recurrence during the 12-month follow-up, while NLR and GFR <60 ml/min/1.73 m2 were associated with VES relapse.

Regression of Coronary Fatty Plaque and Risk of Cardiac Events According to Blood Pressure Status: Data From a Randomized Trial of Eicosapentaenoic Acid and Docosahexaenoic Acid in Patients With Coronary Artery Disease

Background Residual risk of cardiovascular events and plaque progression remains despite reduction in low-density lipoprotein cholesterol. Factors contributing to residual risk remain unclear. The authors examined the role of eicosapentaenoic acid and docosahexaenoic acid in coronary plaque regression and its predictors. Methods and Results A total of 240 patients with stable coronary artery disease were randomized to eicosapentaenoic acid plus docosahexaenoic acid (3.36 g/d) or none for 30 months. Patients were stratified by regression or progression of coronary fatty plaque measured by coronary computed tomographic angiography. Cardiac events were ascertained. The mean±SD age was 63.0±7.7 years, mean low-density lipoprotein cholesterol level was <2.07 mmol/L, and median triglyceride level was <1.38 mmol/L. Regressors had a 14.9% reduction in triglycerides that correlated with fatty plaque regression (r=0.135; P=0.036). Compared with regressors, progressors had higher cardiac events (5% vs 22.3%, respectively; P<0.001) and a 2.89-fold increased risk of cardiac events (95% CI, 1.1-8.0; P=0.034). Baseline non-high-density lipoprotein cholesterol level <2.59 mmol/L (100 mg/dL) and systolic blood pressure <125 mm Hg were significant independent predictors of fatty plaque regression. Normotensive patients taking eicosapentaenoic acid plus docosahexaenoic acid had regression of noncalcified coronary plaque that correlated with triglyceride reduction (r=0.35; P=0.034) and a significant decrease in neutrophil/lymphocyte ratio. In contrast, hypertensive patients had no change in noncalcified coronary plaque or neutrophil/lymphocyte ratio. Conclusions Triglyceride reduction, systolic blood pressure <125 mm Hg, and non-high-density lipoprotein cholesterol <2.59 mmol/L were associated with coronary plaque regression and reduced cardiac events. Normotensive patients had greater benefit than hypertensive patients potentially due to lower levels of inflammation. Future studies should examine the role of inflammation in plaque regression. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT01624727.

The Association between Neutrophil-to-Lymphocyte Ratio and Glycemic Control in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Background

Glycated hemoglobin (HbA1c) is a commonly used clinical marker to monitor the control of type 2 diabetes mellitus patients (T2DM). However, it is unable to identify the ongoing inflammatory changes in the body. These factors could be easily identified and monitored by the neutrophil-to-lymphocyte ratio (NLR). Therefore, this study is aimed at investigating the relationship between NLR and glycemic control in T2DM.

Method

A comprehensive search of eligible studies was performed in various databases published until July 2021. A random effect model was used to estimate the standardized mean difference (SMD). A metaregression, subgroup, and sensitivity analysis were conducted to search for potential sources of heterogeneity.

Result

A total of 13 studies were included in this study. Accordingly, the SMD of the NLR values between the poor and good glycemic control groups was 0.79 (95% CI, 0.46-1.12). Our study also showed that high NLR was significantly associated with poor glycemic control in T2DM patients (OR = 1.50, 95% CI: 1.30-1.93).

Conclusion

The results of this study suggest an association between high NLR values and an elevated HbA1C in T2DM patients. Therefore, NLR should be considered a marker of glycemic control in addition to HbA1c in T2DM patients.

The Role of Neutrophils in Lower Limb Peripheral Artery Disease: State of the Art and Future Perspectives

In recent years, increasing attention has been paid to the role of neutrophils in cardiovascular (CV) disease (CVD) with evidence supporting their role in the initiation, progression, and rupture of atherosclerotic plaque. Although these cells have long been considered as terminally differentiated cells with a relatively limited spectrum of action, recent research has revealed intriguing novel cellular functions, including neutrophil extracellular trap (NET) generation and inflammasome activation, which have been linked to several human diseases, including CVD. While most research to date has focused on the role of neutrophils in coronary artery and cerebrovascular diseases, much less information is available on lower limb peripheral artery disease (PAD). PAD is a widespread condition associated with great morbidity and mortality, though physician and patient awareness of the disease remains low. To date, several studies have produced some evidence on the role of certain biomarkers of neutrophil activation in this clinical setting. However, the etiopathogenetic role of neutrophils, and in particular of some of the newly discovered mechanisms, has yet to be fully elucidated. In the future, complementary assessment of neutrophil activity should improve CV risk stratification and provide personalized treatments to patients with PAD. This review aims to summarize the basic principles and recent advances in the understanding of neutrophil biology, current knowledge about the role of neutrophils in atherosclerosis, as well as available evidence on their role of PAD.

FIB-4 Index and Neutrophil-to-Lymphocyte-Ratio as Death Predictor in Coronary Artery Disease Patients

Nonalcoholic fatty liver disease (NAFLD)-associated liver fibrosis is likely related to coronary artery disease (CAD) by the mediation of systemic inflammation. This study aimed at evaluating the predictive value of neutrophil-to-lymphocyte-ratio (NLR) and fibrosis-4 index (FIB-4), indices of inflammation and fibrosis, respectively, on CAD mortality. Data from 1460 CAD patients (1151 males, age: 68 ± 10 years, mean ± SD) were retrospectively analyzed. Over a median follow-up of 26 months (interquartile range (IQR) 12−45), 94 deaths were recorded. Kaplan−Meier survival analysis revealed worse outcomes in patients with elevation of one or both biomarkers (FIB-4 > 3.25 or/and NLR > 2.04, log-rank p-value < 0.001). In multivariate Cox regression analysis, the elevation of one biomarker (NLR or FIB-4) still confers a significant independent risk for mortality (hazard ratio (HR) = 1.7, 95% confidence interval (95% CI): 1.1−2.7, p = 0.023), whereas an increase in both biomarkers confers a risk corresponding to HR = 3.5 (95% CI: 1.6−7.8, p = 0.002). Categorization of patients with elevated FIB-4/NLR could provide valuable information for risk stratification and reduction of residual risk in CAD patients.

Nonalcoholic Fatty Liver Disease-Associated Liver Fibrosis Is Linked with the Severity of Coronary Artery Disease Mediated by Systemic Inflammation

METHODS AND RESULTS

We conducted a retrospective study of 531 patients with ultrasonogram-confirmed NAFLD who underwent percutaneous coronary intervention (PCI). Then, all patients were separated into four categories by Gensini score (0, 0-9, 9-48, and ≥48) for use in ordinal logistic regression analysis to determine whether NAFLD fibrosis was associated with increased Gensini scores. Mediation analysis was used to investigate whether systemic inflammation is a mediating factor in the association between NAFLD fibrosis and CAD severity. FIB - 4 > 2.67 (OR = 5.67, 95% CI 2.59-12.38) and APRI > 1.5 (OR = 14.8, 95% CI 3.24-67.60) remained to be independent risk factors for the severity of CAD after adjusting for conventional risk factors, whereas among the inflammation markers, only neutrophils and neutrophil-to-lymphocyte ratio (NLR) were independently associated with CAD. Multivariable ordinal regression analysis suggested that increasing Gensini score (0, 0-9, 9-48, and ≥48) was associated with advanced NAFLD fibrosis. ROC curve showed that either fibrosis markers or inflammation markers, integrating with traditional risk factors, could increase the predictive capacity for determining CAD. Inflammation markers, especially neutrophils and NLR, were mediators of the relationship between NAFLD fibrosis and CAD severity.

CONCLUSIONS

NAFLD patients with advanced fibrosis are at a high risk of severe coronary artery stenosis, and inflammation might mediate the association between NAFLD fibrosis and CAD severity.

Neutrophil/lymphocyte ratio predicts in-hospital complications in Takotsubo syndrome. Results from a prospective multi-center registry

Background

Several hematological indices including subtypes of leukocytes populations have been associated with cardiovascular outcome. Takotsubo syndrome (TTS) is a form of acute heart failure syndrome featured by several in‐hospital complications (IHCs).

Hypothesis

Hematological indices at admission may predict IHCs in TTS patients.

Methods

One hundred and sixty consecutive patients with TTS were enrolled in a multicenter prospective registry. Clinical data, admission hemogram, and IHCs were recorded.

Results

Incidence of IHCs was 37%, including pulmonary edema 9%, cardiogenic shock 9%, need of invasive ventilation 10%, death 8%, stroke 2.5%, and left ventricular thrombi 6%.

Patients with IHCs were older, more frequently male, with physical stressor‐induced TTS, lower left ventricular ejection fraction at admission. Neutrophil/lymphocyte ratio (NLr) (12 ± 12 vs 7 ± 8, P = .002) and white blood cells/mean platelet volume ratio (1.2 ± 0.5 vs 1.0 ± 0.5, P = .03) at admission were significantly higher in patients with IHCs.

NLr values were predictor of IHCs (Odds ratios [OR] 1.07, 95% CI 1.03‐1.11, P < .01). When stratified according to NLr into tertiles, the rate of IHCs was from first to third tertile was, respectively, 22%, 31%, and 58%. NLr values in the higher tertile were independent predictors of IHCs even at multivariate analysis (OR 3.7, 95% CI 1.5‐9.4, P < .01).

NLr values higher than 5 were able to predict IHCs with a sensitivity of 82% and specificity of 58%; negative predictive power was 84% (area under the ROC curve 0.73).

Conclusions

NLr is an independent predictor of IHCs in patients admitted with TTS. Admission hemogram may represent a potential tool for prediction of IHCs in TTS.

Neutrophil to Lymphocyte Ratio Predicts Adverse Cardiovascular Outcome in Peritoneal Dialysis Patients Younger than 60 Years Old

Background

Neutrophil to lymphocyte ratio (NLR) is a new inflammatory marker; the relationship between NLR and adverse cardiovascular (CV) prognosis has been gradually emphasized in the general population. However, their association in peritoneal dialysis (PD) patients remains unclear.

Methods

From January 1, 2010, to May 31, 2017, a total of 1652 patients were recruited. NLR was categorized in triplicates: NLR ≤ 2.74, 2.74 < NLR ≤ 3.96, and NLR > 3.96. Kaplan-Meier cumulative incidence curve and multivariable COX regression analysis were used to determine the relationship between NLR and the incidence of adverse CV outcome, while a competitive risk model was applied to assess the effects of other outcomes on adverse CV prognosis. Besides, forest plot was investigated to analyze the adverse CV prognosis in different subgroups.

Results

During follow-up, 213 new-onset CV events and 153 CV disease (CVD) deaths were recorded. Multivariable COX regression models showed that the highest tertile of NLR level was associated with increased risk of CV events (HR = 1.39, 95%CI = 1.01‐1.93, P = 0.046) and CVD mortality (HR = 1.81, 95%CI = 1.22‐2.69, P = 0.003), while compared to the lowest tertile. Competitive risk models showed that the differences in CV event (P < 0.001) and CVD mortality (P = 0.004) among different NLR groups were still significant while excluding the effects of other outcomes. In subgroups, with each 1 increased in the NLR level, adjusted HR of new-onset CV event was 2.02 (95%CI = 1.26 − 3.23, P = 0.003) and CVD mortality was 2.98 (95%CI = 1.58 − 5.62, P = 0.001) in the younger group (age < 60 years).

Conclusions

NLR is an independent risk factor for adverse CV prognosis in PD patients younger than 60 years old.

Neutrophil Lymphocyte Ratio and Cardiovascular Disease Risk: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review aimed to measure the association between neutrophil lymphocyte ratio (NLR) and cardiovascular disease (CVD) risk.

METHODS

Relevant studies were identified from Medline and Scopus databases. Observational studies with NLR as a study factor were eligible for review. The outcomes of interest were any type of CVD including acute coronary syndrome, coronary artery disease, stroke, or a composite of these cardiovascular events. Mean differences in NLR between CVD and non-CVD patients were pooled using unstandardized mean difference (USMD). Odds ratios of CVD between high and low NLR groups were pooled using a random effects model.

RESULTS

Thirty-eight studies (n=76,002) were included. High NLR was significantly associated with the risks of CAD, ACS, stroke, and composite cardiovascular events with pooled ORs of 1.62 (95% CI: 1.38-1.91), 1.64 (95% CI: 1.30, 2.05), 2.36 (95% CI: 1.44, 2.89), and 3.86 (95% CI: 1.73, 8.64), respectively. In addition, mean NLRs in CAD, ACS, and stroke patients were significantly higher than in control groups.

CONCLUSION

High NLR was associated with CAD, ACS, stroke, and composite cardiovascular events. Therefore, NLR may be a useful CVD biomarker.

Tumour immunogenicity, antigen presentation and immunological barriers in cancer immunotherapy

Since the beginning of the 20^th century, scientists have tried to stimulate the anti-tumour activities of the immune system to fight against cancer. However, the scientific effort devoted on the development of cancer immunotherapy has not been translated into the expected clinical success. On the contrary, classical anti-neoplastic treatments such as surgery, radiotherapy and chemotherapy are the first line of treatment. Nevertheless, there is compelling evidence on the immunogenicity of cancer cells, and the capacity of the immune system to expand cancer-specific effector cytotoxic T cells. However, the effective activation of anti-cancer T cell responses strongly depends on efficient tumour antigen presentation from professional antigen presenting cells such as dendritic cells (DCs). Several strategies have been used to boost DC antigen presenting functions, but at the end cancer immunotherapy is not as effective as would be expected according to preclinical models. In this review we comment on these discrepancies, focusing our attention on the contribution of regulatory T cells and myeloid-derived suppressor cells to the lack of therapeutic success of DC-based cancer immunotherapy.

The influence of natural antibody specificity on antigen immunogenicity

The natural antibody repertoire in humans, apes and Old World primates is distinct from the repertoire of all other placental mammals, and encodes antibodies specific for the carbohydrate epitope Galalpha1-3Galbeta1-4GlcNAc-R (alphaGal). Here, we examined whether conjugating antigens to the alphaGal epitope can augment their immunogenicity in alpha(1,3)galactosyltransferase knockout mice (GT0 mice) which, like humans, produce alphaGal-specific antibodies. Immunization of GT0 mice with BSA conjugated to alphaGal (alphaGal-BSA) led to significant production of anti-BSA IgG antibodies without the need for adjuvant. This response was dependent on the presence of alphaGal-reactive antibodies. Immunization of wild-type mice with alphaGal-BSA failed to induce an anti-BSA response. The presence of alphaGal-reactive antibodies also led to an increase in the T cell response to BSA following immunization with alphaGal-BSA when compared with mice that received BSA alone, resulting in an increased frequency of IFN-gamma- and IL-4-producing BSA-specific T cells. In addition, the ability to produce alphaGal-reactive antibodies enhanced the cytotoxic T lymphocyte anti-viral antigen response following vaccination with murine leukemia virus transformed cell lines that express alphaGal on their cell surface. Natural antibodies that bind alphaGal therefore play a key role in increasing the efficiency of priming to antigens decorated with alphaGal epitopes.

Immunomodulation in progeny from thymectomized primiparous mice exposed to benzo(a)pyrene during mid-pregnancy

Previous studies have shown that Benzo(a)pyrene (B(a)P3) given to non-thymectomized (NTX) female mice alters expression of T cell subsets and suppresses cell mediated immunity (CMI) and humoral immunity (HI) in the progeny. Thus, maternal exposure to B(a)P may influence changes in progeny immune status. To understand how maternal cellular and humoral factors influence embryonic development of progeny immunity, adult female mice were thymectomized (TX) at 6 weeks, mated and injected with 150 microg B(a)P)/g body weight at 12 days of pregnancy. After B(a)P exposure, the following studies were performed: (A) Maternal reproductive capacity and survival rate of progeny; (B) Detection of T cells in progeny thymus; (C) Functional characteristics of progeny thymus or spleen. Maternal thymectomy and B(a)P exposure reduced average litter size by 40%. Serological sensitivity of thymus cells with anti-Thyl + complement occurred at a higher dilution of mAb in progeny from TX mothers exposed to B(a)P, suggesting that B(a)P-thymectomy led to increased sensitivity of developing thymocytes to mAb plus complement. Progeny from TX mothers exposed to B(a)P showed enhanced thymic CMI, but suppressed splenic CMI and HI. Thus, thymectomy prevents CMI immunosuppression by B(a)P, while HI is still suppressed. These results indicate that the maternal thymus is necessary for incurring the effect of B(a)P on progeny CMI.

Temporal changes of suppressor T lymphocytes and cytotoxic T lymphocytes in syngeneic murine malignant gliomas

The temporal activities of suppressor T lymphocytes (Ts) and cytotoxic T lymphocytes (CTL) were investigated in a syngeneic murine malignant glioma (a methylcholanthrene-induced ependymoblastoma of C57BL/6 mouse origin, 203-glioma). After the s.c. tumor inoculation, it was suggested that both Ts and CTL were generated with target specificity against 203-glioma cells, because neither Ts nor CTL activity were seen against syngeneic EL 4 (benzpyrene-induced thymoma), allogeneic P815 (methylcholanthrene-induced mastocytoma of DBA/2 mouse origin) or YAC-1 (Moloney leukemia-induced T-cell lymphoma of A/Sn mouse origin), but only against 203-glioma. It was found that the generation of Ts preceded that of CTL and that the turnover was faster; furthermore, Ts were generated in the thymus and spleen, while CTL were distributed in regional lymph nodes and spleen. Surface marker analysis revealed that only Lyt-1-.2.3+ T-cells participated in suppressor responses in contrast to both Lyt-1-.2.3+ and Lyt-1+.2.3+ T-cells participating in cytotoxic responses. The effects of adult thymectomy (ATx) on the changes of the immunized T-cell subsets were also investigated. In mice thymectomized 3 weeks previously, the Ts activity was abrogated, whereas the CTL activity increased markedly and Lyt-1+.2.3+ T-cells were not detected. The results suggest that CTL or their precursors bearing Lyt-1+.2.3+ phenotype and Ts bearing Lyt-1-.2.3+ phenotype are short-lived lymphocytes. Accordingly, it is suggested that in tumor-bearing mice short-lived Ts are generated earliest with target specificity and, due to the reciprocal relationships between Ts and CTL activities, may have a modulating influence on CTL; furthermore, ATx may alter the patterns of generation of the precursor T-cells and Ts.

Regulation of delayed type hypersensitivity to host histocompatibility antigens during graft-versus-host reactions

During GvH reactions in irradiated mice a variety of specific anti-host immune responses may occur. One of these is the occurrence of DTH to the host histocompatibility antigens, which may account for the inflammatory aspects of GvH. During acute as well as delayed GvH reactions the occurrence of anti-host DTH precedes the clinical symptoms of GvH disease. The anti-host DTH is mediated by long-lived, recirculating Lyt-1 + 2- T cells that need to proliferate in the irradiated recipients in order to display maximum activity. Not all host histocompatibility antigens can elicit anti-host DTH. H-2I and Mls-locus coded alloantigens do, but H-2K/D coded alloantigens and non-H-2 alloantigens other than Mls-locus coded alloantigens do not. This correlates with the ability to elicit proliferative mixed lymphocyte reactions in vitro but is in contrast to the response of nonirradiated mice to sc administered alloantigens. Under the latter conditions, all histocompatibility antigens induce a state of antigen-specific DTH. While the anti-host DTH is mediated by long-lived, recirculating Lyt-1 + 2- T cells, their response can be amplified by short-lived, sessile Lyt-1 + 2 + T cells. The latter T cell subset reacts to the host H-2K/D alloantigens and/or to non-H-2 alloantigens other than Mls-locus coded products. These cells alone cannot mount an anti-host DTH response. The anti-host DTH can be mitigated by Ts cells and non-T suppressor cells. Appropriate Ts cells can be readily induced by iv preimmunization of the donors with 5 X 10(7) irradiated, recipient-type spleen cells. Non-T suppressor cells can be induced by iv injection of bacterial LPS and simultaneous sc injection of 1 X 10(7) recipient type spleen cells. The suppression induced by these protocols shares several characteristics. In both cases the suppression is long-lasting, i.e., lasts at least 50 d, is transferable to syngeneic mice by spleen and lymph node cells, and both suppressive systems affect the induction of anti-host DTH as well as already activated anti-host DTH reactive T cells. Furthermore, while Ts cells and non-T suppressor cells are specific with regard to their antigen recognition, they are both able to suppress the DTH to a completely different set of host alloantigens. This, however, only occurs if the latter are inherited by the irradiated recipients as bystanders to the type of alloantigens that had activated the suppressor cells in the lymphoid cell donors.

Thymic peptide hormones: basic properties and clinical applications in cancer

The manuscript will provide an in-depth and critical review of the nomenclature, biochemistry, biological properties, and a summary of published and on-going clinical trials with all reported thymic preparations, including both partially purified thymic factors (e.g., thymosin fraction 5, thymostimulin) as well as purified and synthesized thymic peptides (e.g., thymosin alpha 1, thymulin). Particular emphasis will be placed on which thymic peptides should be categorized as true hormones. In addition, the comparative biochemistry and biological activity in animals will be summarized and contrasted for all the currently available thymic factors. The effects, in vitro of thymic factors, on peripheral blood lymphocytes isolated from normal donors and patients with primary immunodeficiency disorders, autoimmune disorders, and neoplastic disorders will also be reviewed. Finally, a detailed critical summary of the clinical trials performed with each of the thymic preparations will be presented with an emphasis on treatment of patients with cancer.

Depletion of helper/inducer T cells after thymectomy in myasthenic patients

Using monoclonal anti-T-cell antibodies, we have studied peripheral blood T-cell subsets in 53 patients with myasthenia gravis before and after thymectomy (Tx). Before Tx, the mean OKT4/OKT8 ratio was higher in patients than in controls. Furthermore patients showed a high number of cells reacting simultaneously with the OKT4 and OKT8 antibodies. Shortly after surgery, the helper/suppressor ratio was increased in most of the patients, and the doubly reactive subset decreased to normal levels. However, 6 to 12 months after Tx the OKT4/OKT8 ratio was significantly decreased, particularly in patients showing clinical improvement. The percentage of total T cells was slightly but significantly reduced. A group of 14 patients studied more than 2 years after Tx presented very low OKT4/OKT8 ratios. Thymectomy in MG appears to lead to a gradual decrease of the T-helper subset which could contribute to its favorable effect on the course of the disease.

The immunology of mycobacterial infections

Mycobacteria are endowed with substances that profoundly affect the immune system. Leprosy and tuberculosis exemplify broad spectra of useful and detrimental immune responses of mycobacterial infections that range from intense potentiation to severe specific adn nonspecific suppression of humoral and cellular immune elements. The cellular hypersensitivity induced by mycobacteria serves as a classical model for the analysis of specific and nonspecific immune mechanisms. Mycobacterial disease are prevalent worldwide and rank among the most important bacterial diseases. The kaleidoscope of immunologic events induced by injected mycobacteria and during infections will be reviewed from the standpoint of pathogenesis, pathology, in vitro and in vivo effects on cellular and humoral arms of the immune response, diagnosis, classification, potentiation and suppression.

Thymic abnormalities: antigen or antibody? Response to thymectomy in myasthenia gravis

The therapeutic value of thymectomy for myasthenia is still questioned although it retains an important place among management modalities that strive for sustained remission. Questions derive from uncertainty as to appropriate timing, variable extent of resection and quantitation of response. Forty-seven patients, followed one to seven years, underwent an extended transsternal or combined transcervical-transsternal procedure with anterior mediastinal exenteration. Sixteen have been in complete remission from six months to six years, four are asymptomatic on occasional pyridostigmine and eight are significantly improved. Evaluation of thymic pathology (hyperplasic, involuted areas, and thymoma) included a search for thymic myoid cells by fluorescence cytochemistry. Antibodies to acetylcholine receptor present in 38 of 43, decreased post-operatively to normal in four, by 50% to 80% in 14, by 20 to 50% in three and were unchanged in 14. Most remissions occurred in young women with noninvoluted hyperplastic glands and variably high anti-AChR titers which dropped toward normal in seven of 15. These results encourage us to utilize this procedure routinely.

Immune response to weakly immunogenic virally induced tumors. IX. Mice injected with the in vitro variant of YAC tumor (YAC-1) resist lethal doses of the tumorigenic YAC cells

The ability of the in vitro propagated syngeneic tumor YAC-1 and the allogeneic tumor RBL5 to stimulate cytotoxic cells in A mice, was in correlation with the ability of these tumors to impose in vivo resistance to the viable YAC cells. Similarly, the ability of allogeneic YAC-1 tumor and syngeneic RBL5 tumor to stimulate cytotoxic cells in C57BL/6 mice was in correlation with the ability of these tumors to impose in vivo resistance to the viable RBL5 cells. In contrast, the original in vivo carried YAC tumor cells that induce the appearance of suppressor cells, as measured by in vitro assay, stimulated the in vivo enhancement of tumor growth in A mice. Adult thymectomy delayed the death of A mice injected with viable YAC cells, suggesting that at least some of the cells participating in the tumor enhancement are thymus derived cells.

Thymus cells suppress the in vitro cytotoxic response against trinitrophenyl (TNP) modified syngeneic cells

The regulatory role of adult thymocytes in the in vitro cytotoxic cell formation against TNP-coupled syngeneic spleen cells was studied. Thymocytes are known to amplify the cytoxic response of lymph node cells against allogeneic cells. This kind of synergism was not found in the response against TNP-coupled cells; on the contrary, thymocytes had a clear suppressive effect. Thymocytes inducing this suppression must be present already at the beginning of the in vitro response. Mitotically blocked (mitomycin-C treated) thymocytes but not heat killed or lysed cells were also capable to suppress anti-TNP cytotoxicity.

Regulation of in vitro generation of cell-mediated cytotoxicity. II. Characterization of thymosin-induced suppressor T cells

Thymosin fraction 5 can induce the appearance of suppressor T cells capable of regulating the in vitro generation of cytotoxic T lymphocytes (CTL) in a 5-day allogeneic or syngeneic mixed lymphocyte-tumor culture (MLTC). Characterization of the suppressor cell population demonstrated it to be a nonadherent, cyclophosphamide-sensitive T cell. In addition, adult thymectomy (Tx) eliminated suppressor cell precursors in spleen, pointing to a direct thymic dependence of the population. Kinetic studies showed that the thymosin influence was necessary for at least the first 12 hr of culture in order for optimal suppression to occur. The in vitro-generated suppressor T cells were antigen specific and could be generated with spleen, thymus, or lymph node cell preparations, suggesting the widespread existence of a regulatory T-cell population under direct humoral thymic control.

Demonstration of a thymus derived, splenic suppressor cell responsible for the age-dependent decrease in contact hypersensitivity in the adult mouse

A suppression of contact hypersensitivity to picryl chloride has been demonstrated in adult thymectomized, 4 and 5 1/2 mo-old CBA mice after i.v. injection of spleen cells from intact CBA mice of the same age. The cells signifcantly suppressed the elicitation of the allergic contact sensitivity reaction and this effect could be inhibited by pretreating the cells with anti-Thy 1 serum and complements. The induction phase was found to be unaffected. However, spleen cells from donors which had received an i.v. injection of picryl sulfonic acid suppressed the induction as well as the elicitation phase of the contact dermatitis. On the basis of these results it appears reasonable to conclude that the decline in the ability to develop contact hypersensitivity in aging mice may be due to the development of a splenic suppressor T cell, mainly affecting the elicitation of the contact hypersensitivity reaction.

Cellular antimicrobial immunity

Acquired resistance to infectious disease may be expressed by a predominantly humoral or a cellular mechanism or, more frequently, by a combination of the two. The cellular interactions which are responsible for the induction of the immune response in the skin, lung, intestinal mucosa, genitourinary tract, conjunctiva, and peritoneal cavity are discussed and the role of living or dead vaccines in the induction of acquired resistance is outlined. The host response involves three different cell types: the phagocytic cell (polymorphs or macrophages), the thymus-dependent (T) lymphocyte, and the thymus-independent (B) lymphocyte-plasma cell line. The normal unstimulated phagocytic cell is capable of killing most nonpathogenic bacteria that gain entry to the tissues. However, the presence of opsonic antibodies and activated macrophages is required to eliminate the pathogenic intracellular parasites. Such immunological activation involves the presence of sensitized T-lymphocytes in the lesion. The cellular response is also characterized by the simultaneous development of a state of delayed-type hypersensitivity (DTH), along with the antimicrobial CMI response. A rising humoral response normally develops subsequently. Killed bacterial cells (except when incorporated into Freund's complete adjuvant) induce the humoral response without the CMI reaction so that such vaccines are not able to fully protect the host against the naturally acquired disease. With the development of cell fractionation methods as well as the identification of distinctive cell surface markers, suspensions of B- and T-cells and macrophages can now be prepared for use in increasingly sophisticated transfer and reconstitution studies. The role of the different cell types in the expression of humoral and cellular immunity has been determined, and the effect of various immunopotentiating and immunosuppressive regimens on the immune system as a whole has been evaluated quantitatively. These studies have led to an appreciation of the role played by suppressor B- and T-cells in the interplay of both humoral and cellular components of the host defense system during the development of immune tolerance, desensitization, anergy, autoimmunity, and the expression of an anamnestic immune response following reinfection.

Adult thymectomy prevention of the appearance of suppressor T cells which depress contact sensitivity to picryl chloride and reversal of adult thymectomy effect by thymus extract

Suppressor cells, which depress the passive transfer of contact sensitivity appear in the lymph nodes and spleen of mice injected with picryl sulfonic acid (PSA). These cells produce a soluble suppressor T cell product (s-TCP), and immune lymph node cells incubated in s-TCP fail to transfer contact sensitivity. This paper shows that the appearance of suppressor T cells following the injection of PSA was prevented by adult thymectomy (ATx). ATx also limited the production of s-TCP. However, ATx had no effect on the DNA synthesis which occurs in the lymph nodes of mice injected with PSA. The adverse effect of ATx on suppressor cells was completely reversed by a neonatal thymus graft placed under the renal capsule and partially reversed by grafts given 600 r in vitro and to a limited extent by grafts given 1000 r. The injection of thymus extract also reversed the effect of ATx whereas splenic extract was inactive. It is suggested that the suppressor T cell which depresses contact sensitivity is dependent on the presence of the thymus because it requires a thymus hormone, and not primarily because it belongs to a short-lived population which is rapidly renewed by cells coming from the thymus.

Stimulation of mixed lymphocyte cultures and cytotoxic responses: evidence that T cells express SD but not LD antigens, whereas B cells express both

By separating T and B cells from stimulator spleens it has been found that mixed lymphocyte response (MLR) and cytotoxic cells are generated in responder T cell populations by B but not by T stimulator cells in a wide variety of strain combinations. It is suggested that MLR-stimulating or LD antigens are expressed on B but not T cells, and that their presence is necessary in order to generate cototoxic responses to H-2K and/or H-2D (or SD) antigens which are present on both T and B cells. The finding that B cells and macrophages stimulate MLR is consistent with the hypothesis that Ia antigens, expressed on both these cell types but not on nylon column purified peripheral T cells, are the MLR-stimulating or LD determinants.