T-cell immunodeficiency following cytotoxic antineoplastic therapy: a review

Although cancer itself is immunosuppressive, cytotoxic antineoplastic therapy is the primary contributor to the clinical immunodeficiency observed in cancer patients. The immunodeficiency induced by cytotoxic antineoplastic therapy is primarily related to T-cell depletion, with CD4 depletion generally more severe than CD8 depletion. Myeloablative therapy, dose-intensive alkylating agents, purine nucleoside analogs, and corticosteroids substantially increase the risk of therapy-induced immunosuppression. Restoration of T-cell populations following cytotoxic antineoplastic therapy is a complex process. Efficient recovery of CD4+ T cell populations requires thymic-dependent pathways which undergo an age-dependent decline resulting in prolonged CD4+ T-cell depletion in adults following T-cell-depleting therapy. Total CD8+ T-cell numbers recover in both children and adults relatively quickly post-therapy; however, CD8+ subset disruptions often remain for a prolonged period. The clinical management of patients with therapy-induced T-cell depletion involves the maintenance of a high index of suspicion for opportunistic pathogens, irradiation of blood products, prophylaxis for viral infections, and reimmunization in selected clinical circumstances. Future research avenues include efforts to rapidly rebuild immunity following cytotoxic antineoplastic therapy so that immune-based therapies may be utilized immediately following cytotoxic therapy to target minimal residual neoplastic disease.

Effect of short-term cocaine administration on the immune system of young and old C57BL/6 female mice

It has been shown that either cocaine or aging alone can alter the immune system. Our objective was to study if the immune system of aging mice was more susceptible to the effect of cocaine than the immune system of young mice. We used a short term (20 days) cocaine daily administration protocol. Cocaine only decreased the absolute number of Thy 1+, CD4+, CD8+, IL-2R+, Mac 1+ and B cells, in the spleen of old mice. Old untreated mice had a lower number of Thy 1+ cells in the thymus, and a higher number of cells expressing IL-2R. Cocaine decreased the number of Thy 1+ cells in the thymus of both age groups. Old mice showed a lower number of IgA+ plasma cells in the intestinal lamina propria (ILP) than young mice. Short term cocaine administration provoked a decrease in the number of CD4+ cells in young mice ILP and of CD8+ cells in old mice ILP. Our data suggest that cocaine can potentiate the effect of aging on the thymus and on the mucosal immune system. Taken together, our findings indicate that aging and cocaine can potentiate each other to impairing the host immune system.

Impairment of natural killer cell activity in Chlamydia trachomatis infected individuals

Natural killer (NK) cell activity is impaired in Chlamydia trachomatis-infected patients. The mechanisms behind the altered NK functions are not clear, but data concerning NK and antibody-dependent cellular cytotoxicity (ADCC) activity have been reported. To investigate whether this impairment is related to a defect at the target cell binding and/or the postbinding level, we evaluated highly purified NK cells obtained from 125 C. trachomatis-infected patients and compared them with 101 normal controls for their ability to kill K-562 and U-937 cell lines using a 51Cr release assay; release tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma); and kill anti-IgM preincubated P-815 cell line (ADCC activity). We found a decrease in the lytic capability of NK cells from C. trachomatis-infected patients against target cell lines; decreased ability to kill bound target cells; and low levels of released TNF-alpha and INF-gamma after incubation with U-937 cells. Taken together, these findings suggest that the impaired NK cell reaction during chlamydial infection is related to defects both at the target and postbinding levels. However, the precise mechanisms remain to be determined. The inability to restore normal NK activity after long-term culture in the presence of high levels of recombinant IL-2 support the hypothesis of an anergic process during chlamydial infection.

Effects of tramadol and its enantiomers on Concanavalin-A induced-proliferation and NK activity of mouse splenocytes: involvement of serotonin

The centrally acting analgesic drug tramadol is a 1:1 racemic mixture of two enantiomers, with different pharmacological properties. The (-)-tramadol preferentially inhibits noradrenaline uptake, whereas the (+)-tramadol inhibits serotonin uptake and binds to opioid receptors. Since tramadol has been shown to stimulate some immune responses in mice, in the present work we analyzed the effects of its enantiomers on the same parameters, with the aim to better characterize the mechanisms involved in such action of tramadol. The acute administration of 20 and 40 mg/kg of racemic tramadol and of 10 and 20 mg/kg of (+)-tramadol induced a significant and comparable stimulation of Concanavalin-A (Con-A) induced proliferation and of Natural Killer (NK) activity of splenocytes. On the contrary, the (-)-tramadol was devoid of any effect. The pretreatment with the serotoninergic antagonist metergoline (3.0 mg/kg) completely blocked the effects of both tramadol and (+)-tramadol. We suggest that the enhancement of the serotoninergic tone could be at the basis of the stimulatory effects exerted by tramadol on Con-A induced lymphoproliferation and NK activity.

Antioxidant administration inhibits exercise-induced thymocyte apoptosis in rats

PURPOSE

The purpose of this study was to investigate the effect of antioxidant on exercise-induced apoptosis in rat thymocytes.

METHODS

After exercise at 13.8 m x min(-1) for 60-90 min x d(-1) on a motor-driven drum exerciser for 2 consecutive days, rat thymocyte apoptosis was monitored by the feature of DNA fragmentation. To study the effect of antioxidant, rats were administered with butylated hydroxyanisole (BHA) for 7 d before exercise.

RESULTS

Exercise could induce thymocyte DNA fragmentation as detected on electrophoretic gel and by cell death detection ELISA kit. Further studies indicated that pretreatment with antioxidant BHA to rats resulted in a blockage of exercise-induced DNA fragmentation. The concentrations of glutathione (GSH) were not significantly changed in rat thymocytes after exercise with or without BHA treatment.

CONCLUSION

These results suggest that reactive oxygen species may play a role in thymocyte apoptosis induced by exercise. However, changes in GSH levels were not observed in this exercise model.

Tumor gangliosides inhibit the tumor-specific immune response

Tumor gangliosides are highly immunosuppressive membrane glycosphingolipids that are shed into the tumor cell microenvironment. We directly tested the impact of shed gangliosides on the in vivo antitumor immune response in a syngeneic fully autochthonous system (FBL-3 erythroleukemia cells, C57BL/6 mice, and highly purified FBL-3 cell gangliosides). The major FBL-3 ganglioside was identified as GM1b by mass spectrometry. Substantial ganglioside shedding (90 pmol/108 cells/h), a requisite for their inhibition of the immune function of tumor-infiltrating leukocytes, was detected. Immunosuppression by FBL-3 gangliosides was potent; 5-20 microM inhibited the tumor-specific secondary proliferative response (80-100%) and suppressed the generation of tumor-specific CTLs (97% reduction of FBL-3 cell lysis at an E:T ratio of 100:1). In vivo, coinjection of 10 nmol of FBL-3 gangliosides with a primary FBL-3 cell immunization led to a reduced response to a secondary challenge (the increase in the draining popliteal lymph node mass, cell number, and lymphocyte thymidine incorporation were lowered by 70, 69, and 72%, respectively). Coinjection of gangliosides with a secondary tumor challenge led to a 61, 74, and 42% reduction of the increase in lymph node mass, cell number, and thymidine uptake and a 63-74% inhibition of the increase of draining lymph node T cells (CD3+), B cells (CD19+), and dendritic cells/macrophages (Mac-3+). Overall, the clear conclusion that tumor-derived gangliosides inhibit syngeneic antitumor immune responses implicates these molecules as a potent factor in promoting tumor formation and progression.

Effect of a single or repeated dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on T cell subpopulations in the Long-Evans rat

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure results in adverse effects on the immune system of experimental animals. The purpose of this study was to compare the effects of a single and repeated dosing of TCDD on splenic T-cell subpopulations in Long Evans rats 9 days post-exposure to TCDD. A single dose (25 microg/kg body weight) of TCDD resulted in reduced body weight. The percentage and total number of CD4+ or CD8+ subsets and percentage of CD4+ or CD8+ cell cycling in the S and G2M phases were similar in the single dosed (25 microg/kg body weight) TCDD group compared with the vehicle control. A repeated dose (5 microg/kg/day for 5 days) of TCDD also resulted in a significant reduction in body weight. However, multiple doses of TCDD significantly decreased the percentage of the CD4+ subset and the percentage of CD4+ cells cycling in the S and G2M phases. No significant change occurred in the CD8+ cell subpopulation after single or multiple dosing with TCDD. These results demonstrated that repeated dosing of TCDD decreased the total percentage of CD4+ cells and the percentage of CD4+ cells cycling 9 days post-exposure, while an analogous single dose of TCDD failed to affect the CD4+ cell subpopulation. The difference in biological responses to a single versus 'equivalent' multiple (cumulative) dose of TCDD is discussed.

[Effect of immunomodulators of varying nature on the expression of lymphocyte markers in melanoma patients]

The influence of immunomodulators such as tactivin, thymalin, gangliin and translam on expression of lymphocyte markers in patients with melanoma was studied. It was shown in vitro that sensitivity of the lymphocyte receptors of melanoma patients to the immunomodulators was individual and depended on the initial level of the marker expression and the drug properties. Preliminary determination of sensitivity of the immunoregulatory cells to the immunomodulators lays the basis for the use of adequate immunocorrecting therapy in the complex treatment of oncologic patients. Gangliin and translam are membrane active compounds influencing the structure and function of lymphocytic membranes. They are considered as a promising class of immunomodulators with diverse spectra of immunotropic action and various fields of practical use.

Lymphocyte subsets as prognostic markers for cancer patients receiving immunomodulative therapy

Immunogenic features of some malignancies have aroused interest in immunotherapy of cancer. Immunotherapy seems most effective in patients with a small tumour burden, and the focus of immunotherapy trials has, thus, lately been on adjuvant treatment. To enable further development of immunotherapy we need to know more about the mechanisms involved in host defence, especially when the system is influenced by extrinsic factors, that is, immunomodulative agents. T lymphocytes play an important role in the host defence against tumour cells trying to escape from immune surveillance. The mechanisms that regulate the host defence systems are complex, and the influence of extrinsic factors such as immunotherapeutic agents is poorly understood. Most data on lymphocyte subsets in malignant disease originate from melanoma or renal cell carcinoma (RCC) studies, although there are scattered data on lymphocyte subsets also in other malignancies. There are several studies implying that the relative amount of CD4+, CD8+, and natural killer (NK) cells may be important and that, by reducing the tumour burden or by using different therapeutic agents, we can stimulate the host defence. However, only some of these studies imply that these changes can have an impact on clinical outcome and prognosis. The findings of the studies reviewed in this paper are mostly encouraging, but whether the lymphocyte subsets have any value as prognostic markers in patients with malignancies receiving immunotherapy is still unclear. Large randomized immunotherapy trials including an observation arm give an ideal opportunity to recognize those immunological changes that are due to therapy, related to the natural host defence, or whether they have any prognostic value.

The induction of distinct cytokine cascades correlates with different effects of granulocyte-colony stimulating factor and granulocyte/macrophage-colony-stimulating factor on the lymphocyte compartment in the course of high-dose chemotherapy for breast cancer

The availability of the myeloid hemopoietic growth factors (HGF) granulocyte- and granulocyte/macrophage-colony stimulating factor (G-CSF and GM-CSF) has enhanced the therapeutic index of high-dose chemotherapeutic antitumoral regimens (HDCT), as well as the rate of severe damage to immune competence. We investigated some immune functions before, during and after one course of HDCT for poor-risk breast cancer and compared the effects of G-CSF and GM-CSF on the immune recovery. They exerted different influences on the functions we examined and showed distinctive patterns of both qualitative and quantitative in vivo activities on the immune system. The main findings were that (a) granulocyte and lymphocyte recovery rates were faster in the patients receiving G-CSF; (b) looking at the lymphocyte compartment, this difference was restricted to the CD3(+)/CD8(+) and CD56(+) lymphocyte subsets; (c) the reconstitution rate of CD19(+) lymphocytes was slow in both groups; (d) at the end of follow-up HLA-DR expression by CD3(+) lymphocytes was higher in the GM-CSF group; (e) the lymphocyte proliferative capacity was restored at a faster rate in the GM-CSF group, whereas cytotoxic activities recovered better in the G-CSF group; (f) the early repopulating phase was characterized by higher interleukin-6 serum levels in the GM-CSF group. Overall, GM-CSF seemed to exert an earlier effect on all T lymphocyte subsets, preventing them from a complete drop during the long-lasting "nadir" of the cell count, whereas G-CSF appeared to boost them strongly, though a few days later, hastening their final recovery. The distinct pattern of the cytokine cascade induced by each factor, consistent with the different functional changes, seemed to account for the peculiarities of their immune modulations.

Human peripheral blood contains two distinct lineages of dendritic cells

Human peripheral blood contains two populations of dendritic cells (DC) but their developmental relationship has not been established. Freshly isolated CD11c- DC possessed a lymphoid morphology, lacked myeloid markers but expressed lymphoid markers (CD4+ CD10+) whilst the CD11c+ DC were monocytoid in appearance and expressed myeloid markers. Although both populations were allostimulatory, only the CD11c+ DC were able to take up antigen. Irrespective of the culture conditions the CD11c- cells developed into CD11c- CD13- CD33- CD4+ CD1a- CD83+/- DC. In contrast, cultured CD11c+ cells developed the phenotype CD11c+ CD13+ CD33+/- CD4- CD1a+ CD83+ CD9+. Only the CD11c+ DC expressed macrophage colony-stimulating factor (M-CSF) receptor and gave rise to CD14+, esterase+, phagocytic macrophages when cultured in M-CSF. These data suggest that these two populations of DC represent distinct lineages of antigen-presenting DC.

Differential modulation of interleukin-4 and interleukin-13 secretion from human peripheral blood mononuclear cells

Interleukin-4 (IL-4) and IL-13 which have been implicated in the pathogenesis of atopic reactions elicit many of the same biologic responses. Therefore, time- and stimulus-dependent differences in the regulation of IL-4 and IL-13 production could be of relevance to their biological effects. In this study we tested the hypothesis that stimulation of peripheral blood mononuclear cells (PBMCs) with different inducers of cell activation would result in a differential expression of IL-4 and IL-13. For this purpose, PBMCs of nonatopic volunteers were incubated with phytohaemagglutinin (PHA), phorbolester (PMA), calcium ionophore A23187, or IL-3. The effect of these stimuli on IL-4 and IL-13 production were analysed by enzyme-linked immunoassay (ELISA) in supernatants of cultured PBMCs. Incubation of PBMCs with A23167 and PHA induced both a dose- and time-dependent increase in IL-4 and IL-13 release. A23187 induced concentrations of IL-4 were higher than those of IL-13 whereas IL-4 release following stimulation with PHA was considerably higher for IL-13 compared to IL-4. In contrast, there was a selective increase in IL-13 but not IL-4 concentrations following stimulation of PBMCs with PMA and IL-3 in vitro. In conclusion in this study evidence is provided that IL-4 and IL-13 production are regulated differently which might explain their functional redundancy.

[Development of lymphocyte subsets in tumor patients after subcutaneous administration of mistletoe extracts]

OBJECTIVE

In order to exclude the possibility that mistletoe therapy may result in immunosuppression, as indicated by a significant reduction of defined lymphocyte subsets,

PATIENTS AND METHODS

peripheral blood cells of 23 tumour patients were treated subcutaneously with increasing concentrations of aqueous mistletoe extracts (Helixor(R)).

RESULTS AND CONCLUSIONS

Within an observation period of 7 months, the relative amount of lymphocytes and the number of natural killer (NK) cells increased while the number of lymphocyte subsets (i. e. CD19+ B cells, CD4+ T helper cells, CD8+ CD28- suppressor cells, CD8+ CD28+ cytotoxic cells) and the proportion of CD25+ (activated) cells within T cells showed a statistically remarkable trend; due to the multiple test problem of statistical evaluation this trend is not allowed to be termed significant. The leucocytes decreased insignificantly within the observation period. However, we were unable to verify a suggested increase of defined lymphocyte subsets within 2-3 months after the onset of mistletoe treatment. Nevertheless, for the parameters CD19+ B cells, CD4+ T helper cells, CD8+ cells, CD8+ CD28+ cytotoxic cells and CD16+/CD56+ NK cells we observed statistically remarkable peaks within die 2nd and 3rd month of therapy, confirming the hypothesis. The responses to the extracts were obviously interindividually different; the immune responses especially of patients with a lower number of peripheral T cells were less significant as compared to those of patients with adequate T cell numbers. Surprisingly, even an increase of the drug concentration >3 ng mistletoe lectin (as determined within the whole plant extract) per kg body weight enhanced the number of CD4+ T helper cells. A decreased immunological reaction on mistletoe extracts was shown especially for patients with a reduced number of peripheral T cells, whereas patients with normal T-cell number were more reactive.

Lansoprazole decreases peripheral blood monocytes and intercellular adhesion molecule-1-positive mononuclear cells

We examined the effects of lansoprazole, a proton-pump inhibitor, on peripheral blood mononuclear cells in healthy subjects in comparison with ranitidine. Ten healthy volunteers were randomly divided into two groups and given either lansoprazole (30 mg daily for 2 days) or ranitidine (150 mg daily for 21 days). Peripheral blood was collected before and 7, 14, and 21 days after the start of treatment. Mononuclear cells were isolated by densitometric centrifugation and were examined for adhesion molecules (ICAM-1, VLA4, SLe(x)), membrane markers of the monocyte/macrophage series, and lymphocyte phenotypes. The number of cells expressing adhesion molecules, the number of monocytes/macrophages, and lymphocyte phenotypes were the same in Helicobacter pylori-positive and -negative subjects. The number of cells expressing ICAM-1 was significantly decreased seven days after the start of lansoprazole treatment, and this change persisted until day 14, while ranitidine had no effect. The number of monocytes (identified by Leu-M3 positivity) was decreased seven days after the start of treatment in both groups, but predominantly in the lansoprazole group. No other changes were observed on administration of either drug. These results suggest that short-term treatment with lansoprazole causes persistent inhibition of inflammatory responses irrespective of the presence of H. pylori infection. This effect may indicate a possible new mechanism of action of proton-pump inhibitors other than inhibition of acid secretion.

Investigation of some immunological functions in a group of asphalt workers exposed to polycyclic aromatic hydrocarbons

To investigate the effects of polycyclic aromatic hydrocarbons (PAHs) on the human immune system, analyses were performed on T-cell subsets (CD4+, CD8+), B-cells (CD19+), serum immunoglobulin levels (IgG, IgM, IgA) and white blood cell percentages of 16 male workers who were employed in road paving operations and compared to 12 unexposed male controls. PAH exposure was assessed using urinary 1-hydroxy-pyrene (1-OHP) levels and was found to be significantly higher in workers than in the controls. While the CD4+ cell percentage and the CD4+/CD8+ ratio were significantly higher in the PAH-exposed group, the percentages of CD8+ and CD19+ cells were unchanged. There was also a significant enhancement in serum IgG levels and the percentage of monocytes in the workers compared to the control group. These data suggest that chronic exposure to PAHs may affect some immune functions in humans.

Phase I study of the novel cyclic AMP (cAMP) analogue 8-chloro-cAMP in patients with cancer: toxicity, hormonal, and immunological effects

The cyclic AMP (cAMP)-dependent protein kinase regulatory subunit RI is overexpressed in cancer cells. 8-Chloro-cAMP (8-Cl-cAMP) is an RII site-specific analogue that down-regulates RI and inhibits the growth of a wide range of cancer cells in vitro and in vivo. We performed a Phase I trial of 8-Cl-cAMP in 32 patients with malignancies that were refractory to standard treatments. 8-Cl-cAMP was initially given in a 1-month cycle by constant infusion at 0.005 mg/kg/h for 21 days, followed by 1 week of rest. The dose was escalated to 0.045 mg/kg/h, but hypercalcemia became the dose-limiting toxicity. The length of drug administration was, therefore, reduced to 5 days per week for the first 3 weeks of the cycle, but it was not possible to increase the drug dose without producing hypercalcemia. Hence, the length of drug administration was reduced to 3 days per week for the first 3 weeks of the cycle. The maximum tolerated dose for this regimen was 0.15 mg/kg/h, and the dose-limiting toxicities were reversible hypercalcemia and hepatotoxicity. Stable disease for > or =4 months was observed in two patients treated at > or =0.045 mg/kg. cAMP-dependent protein kinase is involved in hormone- and cytokine-mediated signaling, and so representative hormone, cytokine, and peripheral lymphocyte subsets were measured. The drug had a parathyroid hormone-like effect on calcium homeostasis and significantly increased circulating luteinizing hormone and 17-hydoxyprogesterone levels (P < 0.02 and P < 0.0006, respectively). We conclude that 8-Cl-cAMP is well tolerated without attendant myelotoxicity, and in this study, it was associated with biological effects. In Phase II studies, a dose of 0.11 mg/kg/h for 3 days per week would be appropriate.

Lymphocyte subsets and inflammatory mediators in patients with subacute sclerosing panencephalitis

A defective cell-mediated immunity and inflammatory cytokines are suggested in the pathogenesis of subacute sclerosing panencephalitis. In this study we analyzed lymphocyte subsets in peripheral blood and concentrations of interleukin-1alpha (IL-1alpha), interleukin-2 (IL-2alpha), tumor necrosis factor-alpha (TNF-alpha), and platelet activating factor in plasma and cerebrospinal fluid before and after immunomodulatory therapy (interferon-alpha plus isoprinosine) in three patients with subacute sclerosing panencephalitis. Increased percentage of CD8+cells (T-suppressor/cytotoxic cell) and CD16+CD56+cells (NK cell) and reduced percentage of CD3+/HLA-DR+ (active T-cell) and CD3+ (total T-cell) cells were found before therapy. After immunomodulatory therapy, CD3+/HLA-DR+ (active T-cell) cells were markedly increased and there was a slight increase in the percentages of all lymphocyte subsets in the patients. The concentrations of platelet activating factor in plasma and cerebrospinal fluid were higher than the mean value in controls. Cerebrospinal fluid and plasma TNF-alpha and IL-2 levels were nondetectable in two patients who had a stationary course of disease and were markedly elevated in patient 3, who displayed a rapidly progressive course.

Effect of dexamethasone on lymphocyte subpopulations in premature infants with bronchopulmonary dysplasia

OBJECTIVE

This study was designed to determine the effect of dexamethasone treatment on peripheral blood lymphocyte counts and subpopulations in premature infants with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

Peripheral blood lymphocyte subpopulations in 12 premature infants with BPD were analyzed before treatment with a 6-week course of dexamethasone (day 0), on days 3 and 10 of treatment, and 2 weeks after discontinuing dexamethasone therapy (day 56). Lymphocyte immunophenotypes were determined using direct two-color immunofluorescent staining followed by flow cytometry.

RESULTS

The percentage of lymphocytes was significantly lower on days 3 (17.55 +/- 2.55) and 10 (20 +/- 11.8) of dexamethasone therapy compared with before (30.36 +/- 6.41) or after treatment. The percentage of T cells was significantly lower on days 3 and 10 of dexamethasone therapy (mean +/- SEM; 58.09 +/- 1.93 and 60.09 +/- 2.47, respectively) compared with before (67.09 +/- 4.24) or after treatment. The absolute number of T cells was significantly lower on day 10 of therapy. The percentage of CD4+ cells was significantly lower on days 3 (38.91 +/- 2.49) and 10 (40.45 +/- 2.24) of therapy, and this decrease persisted after dexamethasone was stopped (36.73 +/- 3.41). The absolute number of CD4 cells was significantly lower on day 10 (1328 +/- 216) of therapy and reached a nadir on day 56 (1143 +/- 106). Similarly, the CD4/CD8 ratio was also significantly lower on days 3 and 10 of treatment (1.56 +/- 0.18 and 1.64 +/- 0.14, respectively) and reached a nadir on day 56 (1.04 +/- 0.13).

CONCLUSION

Dexamethasone significantly reduced the percentage and absolute number of lymphocytes, T cells, and CD4 cells, as well as the CD4/CD8 ratio. A reduction in CD4 cells and in the CD4/CD8 ratio persisted 2 weeks after dexamethasone therapy was stopped. In contrast, the absolute number of B cells increased transiently, and CD8 cells were unaffected by dexamethasone. This alteration in lymphocyte subpopulations may help account for the clinically beneficial anti-inflammatory effect of dexamethasone in the treatment of BPD complicated by respiratory failure. The dexamethasone-induced decrease in CD4 cells may also increase the susceptibility of these infants to infection.

Lymphocyte subsets and sister-chromatid exchanges in the students exposed to formaldehyde vapor

The present report evaluates the effects of formaldehyde (FA) exposure on peripheral lymphocytes by using both genetic and immunological parameters. Twenty-three non-smoking students in the study had inhalation exposure to 0.508 +/- 0.299 mg/m3 of FA for a period of 8 weeks (3h x 3 times each week) during anatomy classes. As for composition of lymphocyte subsets after FA exposure, significant increase was found in the percentage of CD19 (B cells), while significant decrease was observed in CD3 (total T cells), CD4 (T helper-inducer cells), and CD8 (T cytotoxic-suppressor cells) with a P < 0.01. Increase in the ratio of T-helper-inducer cells to T-cytotoxic-suppressor cells (T4/T8) was also observed with statistical significance after exposure (P < 0.001). In the meanwhile, no significant difference (P > 0.05) was reported between lymphocyte proliferation rate and sister-chromatid exchange (SCE) at the exposure level and duration. It is suggested that the lymphocyte subsets may be most susceptible to the effects of FA, though a single immunological endpoint is rarely related with pathophysiological interpretation.

Induction of Fas ligand (CD95L) by the toxic mistletoe lectins in human lymphocytes

BACKGROUND

Fas ligand (FasL, CD95L) predominantly expressed on activated cytotoxic T cells and NK cells triggers apoptosis in Fas receptor (Apo-1, CD95) positive target cells. We investigated the expression of FasL, Fas and tumor necrosis factor (TNF) receptor 1 (TNF-R1, CD120a) on cultured human lymphocytes and leukemic T and B cells.

MATERIALS AND METHODS

Lymphocytes from six healthy individuals, from four patients with chronic lymphocytic T or B cell leukaemia, and leukemic Molt-4 cells were incubated with the apoptosis- inducing mistletoe lectins (ML I and ML III).

RESULTS

Incubation of differentiated lymphocytes with the ML resulted in a significant upregulation of FasL in the surviving CD4+ T helper cells, CD8+ cells and CD19+ B cells. Similarly, the TNF receptor expression increased, while the Fas molecule decreased. In contrast, FasL was not induced in leukemic cells.

CONCLUSIONS

Apart from a direct induction of apoptosis in response to an inhibition of protein synthesis by the enzymic ML A chain, ML treatment may indirectly induce apoptosis in Fas+ tumour cells through activated FasL+ lymphocytes.

Shiga toxin 1 from Escherichia coli blocks activation and proliferation of bovine lymphocyte subpopulations in vitro

Shiga toxin-producing Escherichia coli (STEC) is widespread in the cattle population, but the clinical significance of Shiga toxins (Stx's) for the bovine species remains obscure. Since Stx's exert immunomodulating effects in other species, we examined the effect of purified Stx1 on a bovine B lymphoma cell line (BL-3) and peripheral blood mononuclear cells (PBMC) isolated from adult bovine blood by viability assays and flow cytometry analysis. Stx1 markedly induced apoptosis in stimulated BL-3 cells. The susceptibility of this B-cell-derived cell line was induced only by either lipopolysaccharide (LPS) or pokeweed mitogen, while cultures stimulated with T-cell mitogens were unaffected by the toxin. In contrast, Stx1 did not induce cellular death-neither apoptosis nor necrosis-in primary cultures of PBMC but hindered the mitogen-induced increase in metabolic activity. The influence of Stx1 on single PBMC subpopulations varied with the type of mitogenic stimulus applied. Stimulation with phytohemagglutinin P particularly induced the proliferation of bovine CD8-expressing (BoCD8(+)) cells, and this proliferative response was blocked by Stx1. On the other hand, Stx1 reduced the portion of viable B cells in the presence of LPS. Modulation of activation marker expression (BoCD25 and BoCD71) by Stx1 indicated that the toxin hindered the proliferation of cells by blocking their activation. In conclusion, we assume that Stx1 contributes to the pathogenesis of STEC-associated diarrhea in calves by suppressing the mucosa-associated immune response. The usefulness of cattle as a model in which to study Stx-induced immunomodulation is discussed.

Indomethacin inhibits circulating PGE2 and reverses postexercise suppression of natural killer cell activity

Natural killer (NK) cells are important in combating viral infections and cancer. NK cytolytic activity (NKCA) is often depressed during recovery from strenuous exercise. Lymphocyte subset redistribution and/or inhibition of NK cells via soluble mediators, such as prostaglandin (PG) E2 and cortisol, are suggested as mechanisms. Ten untrained (peak O2 consumption = 44.0 +/- 3.5 ml. kg-1. min-1) men completed at 2-wk intervals a resting control session and three randomized double-blind exercise trials after the oral administration of a placebo, the PG inhibitor indomethacin (75 mg/day for 5 days), or naltrexone (reported elsewhere). Circulating CD3(-)CD16(+)/56(+) NK cell counts, PGE2, cortisol, and NKCA were measured before, at 0.5-h intervals during, and at 2 and 24 h after a 2-h bout of cycle ergometer exercise (65% peak O2 consumption). During placebo and indomethacin conditions, exercise induced significant (P < 0.0001) elevations of NKCA (>100%) and circulating NK cell counts (>350%) compared with corresponding control values. With placebo treatment, total NKCA was suppressed (28%; P < 0.05) 2 h after exercise, and a postexercise elevation (36%; P = 0.02) of circulating PGE2 was negatively correlated (r = 0.475, P = 0.03) with K-562 tumor cell lysis. NK counts were unchanged in the postexercise period, but at this stage CD14(+) monocyte numbers were elevated (P < 0.0001). Indomethacin treatment eliminated the postexercise increase in PGE2 concentration and completely reversed the suppression of total and per CD16(+)56(+) NKCA 2 h after exercise. These data support the hypothesis that the postexercise reduction in NKCA reflects changes in circulating PGE2 rather than a differential lymphocyte redistribution.

The natural killer T (NKT) cell ligand alpha-galactosylceramide demonstrates its immunopotentiating effect by inducing interleukin (IL)-12 production by dendritic cells and IL-12 receptor expression on NKT cells

The natural killer T (NKT) cell ligand alpha-galactosylceramide (alpha-GalCer) exhibits profound antitumor activities in vivo that resemble interleukin (IL)-12-mediated antitumor activities. Because of these similarities between the activities of alpha-GalCer and IL-12, we investigated the involvement of IL-12 in the activation of NKT cells by alpha-GalCer. We first established, using purified subsets of various lymphocyte populations, that alpha-GalCer selectively activates NKT cells for production of interferon (IFN)-gamma. Production of IFN-gamma by NKT cells in response to alpha-GalCer required IL-12 produced by dendritic cells (DCs) and direct contact between NKT cells and DCs through CD40/CD40 ligand interactions. Moreover, alpha-GalCer strongly induced the expression of IL-12 receptor on NKT cells from wild-type but not CD1(-/-) or Valpha14(-/-) mice. This effect of alpha-GalCer required the production of IFN-gamma by NKT cells and production of IL-12 by DCs. Finally, we showed that treatment of mice with suboptimal doses of alpha-GalCer together with suboptimal doses of IL-12 resulted in strongly enhanced natural killing activity and IFN-gamma production. Collectively, these findings indicate an important role for DC-produced IL-12 in the activation of NKT cells by alpha-GalCer and suggest that NKT cells may be able to condition DCs for subsequent immune responses. Our results also suggest a novel approach for immunotherapy of cancer.

S. aureus superantigen protein A expands CD4(+)/CD8(+)/CD19(+)/CD34(+) cells in mice: a potential immunorestorer

Protein A (PA) of Staphylococcus aureus is known for its immunostimulatory, anti-cancer, and anti-toxic properties. The present study revealed that PA stimulates specific immunocytes to act as a potential immunorestorer. It has also been shown that the percentage of various cell types bearing different clusters of differentiation markers, e.g., CD4(+), CD8(+), CD19(+), increases considerably after inoculation with PA. It has also been observed that CD34(+) progenitor cells of bone marrow also increased significantly (P < 0.05) upon PA treatment. PA significantly elevated Th-1 cytokines, e.g., IFN-gamma, TNF-alpha, and IL-1alpha. The increased percentages of CD4(+), CD8(+), CD19(+), CD34(+) cells and elevated cytokine levels in PA treated animals may contribute to the reported anti-tumor, anti-fungal, anti-parasitic, and anti-toxic properties of PA. Since in various diseased conditions and during toxic drug therapy lymphocytes bearing such differentiation markers get suppressed, this type of approach could help in immunorestoration of the host. These findings might help in designing therapeutic approaches toward various diseases which cause immunosuppression.