Involvement of NK Cells against Tumors and Parasites

Host resistance against pathogens depends on a complex interplay of innate and adaptive immune mechanisms. Acting as an early line of defence, the immune system includes activation of neutrophils, tissue macrophages, monocytes, dendritic cells, eosinophils and natural killer (NK) cells. NK cells are lymphoid cells that can be activated without previous stimulation and are therefore like macrophages in the first line of defence against tumor cells and a diverse range of pathogens. NK cells mediate significant activity and produce high levels of proinflammatory cytokines in response to infection. Their cytotoxicity production is induced principally by monocyte-, macrophage- and dendritic cell-derived cytokines, but their activation is also believed to be cytokine-mediated. Recognition of infection by NK cells is accomplished by numerous activating and inhibitory receptors on the NK cells’ surface that selectively trigger the cytolytic activity in a major histocompability complex-independent manner. NK cells have trypanocidal activity of fibroblast cells and mediate direct destruction of extracellular epimastigote and trypomastigote forms of T. cruzi and T. lewisi in vitro; moreover, they kill plasmodia-infected erythrocytes directly through cell-cell interaction. This review provides a more detailed analysis of how NK cells recognize and respond to parasites and how they mediate cytotoxicity against tumor cells. Also the unique role of NK cells in innate immunity to infection and the relationship between parasites and carcinogenesis are discussed.

The correlation between the subsets of tumor infiltrating memory T cells and the expression of indoleamine 2,3-dioxygenase in gastric cancer

BACKGROUNDS

Although many researchers have concentrated on the mechanism of T cell anergy resulting from over-expression of Indoleamine 2,3-dioxygenase (IDO), it remains unclear what alterations will developed in memory T cells (Tm) under over-expression of IDO.

METHODS

Immunohistochemical staining for IDO expression in gastric cancer tissues (n=50) was carried out. Tumor-infiltrating memory Tm cells were counted by flow cytometry. The association between IDO expression and the subsets of tumor infiltrating Tm are discussed.

RESULTS

The higher IDO expressions were significantly associated with deeper invasion (P=0.016) and higher frequencies (P=0.038) of lymph node metastasis. The lower tumor-infiltrating CD4+Tm were significantly associated with the advanced clinical stage (P=0.026) and lymph node metastasis (P=0.016). The lower percentages of CD8+Tm were significantly related to undifferentiated histological type (P=0.042) and lymph node metastasis (P=0.037). However, the lower percentage of CD8+Tem was significantly correlated to differentiated histological type (P=0.017), lower frequencies of lymph node metastasis (P=0.014), and earlier clinical stage (P=0.008). The higher IDO expression patients had significantly lower percentages of CD4+Tm (P=0.012) and CD8+Tm (P=0.033). Nevertheless, it was confirmed that the higher level of IDO expression correlated with higher percentages of CD8+Tm cells in univariate and multivariate analysis (P=0.011).

CONCLUSION

IDO over-expression and Tm in tumor microenvironments were correlated with the disease stage and histological type of gastric cancer. Higher IDO expression was related to the lower percentage of CD4+Tm and CD8+Tm, whereas the higher level of IDO expression related with a higher percentage of CD8+Tem.

Opportunities to optimize tacrolimus therapy in solid organ transplantation: report of the European consensus conference

In 2007, a consortium of European experts on tacrolimus (TAC) met to discuss the most recent advances in the drug/dose optimization of TAC taking into account specific clinical situations and the analytical methods currently available and drew some recommendations and guidelines to help clinicians with the practical use of the drug. Pharmacokinetic, pharmacodynamic, and more recently pharmacogenetic approaches aid physicians to individualize long-term therapies as TAC demonstrates a high degree of both between- and within-individual variability, which may result in an increased risk of therapeutic failure if all patients are administered a uniform dose. TAC has undoubtedly benefited from therapeutic drug monitoring, but interpretation of the blood concentration is confounded by the relative differences between the assays. Single time points, limited sampling strategies, and area under concentration-time curve have all been considered to determine the most appropriate sampling procedure that correlates with efficacy. Therapeutic trough TAC concentration ranges have changed since the initial introduction of the drug, while still maintaining adequate immunosuppression and avoiding drug-related adverse effects. Pharmacodynamic markers have also been considered advantageous to the clinician, which may better reflect efficacy and safety, taking into account the between-individual variability rather than whole blood concentrations. The choice of method, differences between methods, and potential pitfalls of the method should all be considered when determining TAC concentrations. The recommendations of this consensus meeting regarding the analytical methods include the following: encourage the development and promote the use of analytical methods displaying a lower limit of quantification (1 ng/mL), perform careful validation when implementing a new analytical assay, participate in external proficiency testing programs, promote the use of certified material as calibrators in high-performance liquid chromatography with mass spectrometric detection methods, and take account of the assay and intermethod bias when comparing clinical trial outcomes. It is also important to consider that TAC concentrations may also be influenced by other factors such as specific pharmacokinetic characteristics associated with the population, drug interactions, pharmacogenetics, adverse events that may alter TAC concentrations, and any change in the oral formulation that may result in pharmacokinetic changes. This meeting emphasized the importance of obtaining multicenter prospective trials to assess the efficacy of alternative strategies to TAC trough concentrations whether it is other single time points or area under the concentration-time curve Bayesian estimation using limited sampling strategies and to select, standardize, and validate routine biomarkers of TAC pharmacodynamics.

T-cell function monitoring in stable renal transplant patients treated with sirolimus monotherapy

BACKGROUND

Sirolimus is an agent with lymphocyte-specific features similar to those of calcineurin inhibitors but with a different mechanism of action and safety profile. To optimize the use of sirolimus-based immunosuppression, further investigation of appropriate pharmacokinetic (sirolimus exposure) and pharmacodynamic (sirolimus T-cell immunomodulator effect) monitoring is required to determine personalized target concentrations.

AIM

The main objective of the study was to evaluate the feasibility and reproducibility of combined pharmacokinetic and pharmacodynamic monitoring and to apply biomarkers of immunosuppression in stable kidney transplant recipients receiving sirolimus monotherapy.

METHODS

Fourteen renal transplant patients treated with sirolimus monotherapy (median 2 years) were included in this study. Pharmacokinetic and pharmacodynamic parameters were evaluated in each patient three times: at inclusion in the study (day 1), then again at 3 and 6 months.

RESULTS

The median sirolimus concentration was 11.5 ng/mL. CD4+ T-cell adenosine triphosphate (ATP) concentrations (150 ng/mL) and interleukin (IL)-10 production (50.9 ng/mL) were significantly lower in treated patients than in healthy controls (n = 95) [301 ng/mL; 278 ng/mL, respectively]. Median inhibition of T-cell proliferation was 60% (31-96%) in treated patients. Interferon-gamma and transforming growth factor-beta production was found to be similar to those in the healthy controls. Our results suggest an association between low ATP and IL-10 concentrations and the presence of infection.

CONCLUSIONS

The sequential measurement of these biomarkers in stable renal transplant recipients treated with monotherapy could be useful to evaluate the biological effect of sirolimus in each patient and to establish personalized therapy taking into account the individual response to the drug.

Antidepressant therapy can improve adherence to antiretroviral regimens among HIV-infected and depressed patients

Several strategies have been introduced to manage nonadherence to highly active antiretroviral therapy (HAART). Treatment with antidepressants may improve self-reported adherence. In this brief report, a small sample of HIV-depressed patients (n = 9) were treated for a 6-month period with antidepressants improving self-reported adherence based on the HAART scale (poor, good, satisfactory, and optimal). Before the antidepressant treatment, adherence was reported as "good" by 3 patients and "satisfactory" by 6 patients. After antidepressant therapy, adherence to antiretroviral regimes was statistically higher in HIV-depressed on treatment than in HIV-depressed patients not treated with antidepressants (P < 0.0001). We used chi2 test with a significance level at P < 0.05. Treating depression in HIV-infected patients may serve to improve adherence to HAART.