Naive and memory T lymphocytes migrate in comparable numbers through normal rat liver: activated T cells accumulate in the periportal field

Although the liver is known to contain a significant number of lymphocytes, migration of these through the compartments of the liver, parenchyma and periportal field, has not been studied. The periportal field, in particular, is affected in several immunological disorders of the liver. Populations of labeled naive, activated, and memory T cells were injected into congenic rats. The recipient livers and draining lymph nodes were removed at various time points, and cryostat sections were analyzed for the presence of donor cells using quantitative immunohistology. Donor cell proliferation and apoptosis were examined in vivo by BrdU (5 microM 5-bromo-2-deoxyuridine) incorporation and the TUNEL technique, respectively. Early after injection (0.5-1 h), naive, activated, and memory T cells were localized to the parenchyma and periportal field in comparable numbers. With time, all T cell subsets left the parenchyma but remained or, in the case of activated T cells, significantly accumulated in the periportal field. Furthermore, 12% of activated donor T cells proliferated in vivo within the periportal field, and 0.5% showed evidence of apoptosis. Taken together, not only activated and memory, but also naive T cells continuously migrate through the liver, showing a preference for the periportal field, and activated T cells mainly proliferate there. This may explain why many immunological liver diseases predominantly affect the periportal field.

Lymphocyte subset analyses in blood, spleen and lymph nodes of female Sprague-Dawley rats after short or prolonged exposure to a 50 Hz 100-microT magnetic field

Based primarily on the results of in vitro studies, it has been suggested that power-line (50 or 60 Hz) magnetic fields (MFs) may reduce immune function, which could lower resistance to infection or cancer. This study was conducted to evaluate the influence of acute and chronic in vivo exposure to a linearly polarized 50 Hz MF on immune function in female Sprague-Dawley rats. Groups of rats were exposed continuously to the MF at a flux density of 100 microT for periods of 3 days, 14 days or 13 weeks. For each exposure period, one control group of rats was sham-exposed together with each MF-exposed group. Experimental end points included analyses of T-lymphocyte subsets as well as other immune cells involved in cell-mediated immune responses, i.e. natural killer (NK) cells, B lymphocytes, macrophages, and granulocytes in blood, spleen and mesenteric lymph nodes. In addition, immunohistochemical methods were used to detect proliferating and apoptotic cells in the various compartments of spleen tissue. The results obtained failed to demonstrate a significant effect of short or prolonged MF exposure on different types of leukocytes, including lymphocyte subsets. Furthermore, the experiments on the in vivo proliferation activity of lymphocytes and the extent of apoptosis in spleen samples did not indicate a difference between the MF-exposed and sham-exposed groups, indicating that MF exposure does not affect the mechanisms involved in the control of lymphocyte homeostasis. The lack of MF effects in the immune tests used in the present in vivo study makes it highly unlikely that MF exposure induces immunotoxicity, at least under the experimental conditions used. However, the data do not exclude the possibility that functional alterations in T-cell responses to mitogens and in NK cell activity as recently described for MF-exposed rodents may be one mechanism involved in the carcinogenic effects of MF exposure observed in some models of co-carcinogenesis.

CD95/Fas-triggered apoptosis of activated T lymphocytes is prevented by dendritic cells through a CD58-dependent mechanism

T-cell apoptosis is a mechanism regulating T-cell homeostasis. Activation renders T cells susceptible to activation-induced cell death, a process mediated through CD95 ligand/CD95 (Apo-1/Fas) ligation. The aim of this study was to test whether antigen-presenting cells can inhibit CD95/Fas-triggered activation-induced cell death. Dendritic cells (DC), which are highly effective antigen-presenting cells, were generated in vitro from human peripheral blood monocytes by culture in granulocyte-macrophage colony-stimulating factor and interleukin 4. Subsequently, DC were cocultured with activated T cells and the effect of DC on CD95/Fas-mediated apoptosis was determined. Coculture with increasing amounts of DC prevented CD95/Fas-triggered apoptosis in a dose-dependent fashion by inhibiting activation of caspase 8 and caspase 3. This protective effect of the DC on T-cell death could be blocked by 50% by adding an anti-CD58 antibody, whereas further addition of anti-CD80 (B7.1) and anti-CD86 (B7.2) led to an even more pronounced effect. Our findings suggest that DC can protect T cells from activation-induced cell death, with CD58 ligation playing a key role.

Distribution of activated T cells migrating through the body: a matter of life and death

The preferential distribution of lymphocyte subsets in tissues is attributed to a selective lymphocyte-endothelium interaction during entry. However, proliferation and death within the tissue, and exit from the tissue, might also play a role. Here, Jürgen Westermann and Ulrike Bode provide evidence that preferential survival in the tissue of initial stimulation is the major factor in the preferential distribution of activated T cells.

Conditioned immunosuppression makes subtherapeutic cyclosporin effective via splenic innervation

The present study investigated the mechanisms by which conditioned immunosuppression enhances the effectiveness of cyclosporin A (CsA) treatment in prolonging heart allograft survival. Dark Agouti rats that were administered subtherapeutic CsA (7 x 2 mg/kg on alternate days) rejected heart allografts at the same time as non-CsA-treated rats. The addition of a behavioral conditioning regimen (conditioned stimulus, saccharin; unconditioned stimulus, 20 mg/kg CsA) to the subtherapeutic CsA protocol produced a significant prolongation of graft survival, including long-term survival (>100 days) in 20% of the animals. Prior sympathetic denervation of the spleen completely blocked this effect. In nontransplanted rats both conditioning and CsA treatment reduce interleukin-2 and interferon (IFN)-gamma in the supernatant of proliferating splenocytes. Additionally, therapeutic CsA treatment decreased the number of IFN-gamma-producing CD4(+) naive and memory T cells in the spleen. In contrast, behavioral conditioning increased that number. These data indicate that behavioral conditioning prolongs heart allograft survival by inhibiting the release of these cytokines in the spleen via sympathetic innervation, supplementing the inhibited cytokine production induced by CsA treatment.

Lymphocyte migration in lymphocyte function-associated antigen (LFA)-1-deficient mice

Using lymphocyte function-associated antigen (LFA)-1(-/-) mice, we have examined the role of LFA-1 and other integrins in the recirculation of lymphocytes. LFA-1 has a key role in migration to peripheral lymph nodes (pLNs), and influences migration into other LNs. Second, the alpha4 integrins, alpha4beta7 and alpha4beta1, have a hitherto unrecognized ability to compensate for the lack of LFA-1 in migration to pLNs. These findings are confirmed using normal mice and blocking LFA-1 and alpha4 monoclonal antibodies. Unexpectedly, vascular cell adhesion molecule (VCAM)-1, which is essential in inflammatory responses, serves as the ligand for the alpha4 integrins on pLN high endothelial venules. VCAM-1 also participates in trafficking into mesenteric LNs and Peyer's patch nodes where mucosal addressin cell adhesion molecule 1 (MAdCAM-1), the alpha4beta7-specific ligand, dominates. Both alpha4beta1, interacting with ligand VCAM-1, and also LFA-1 participate in substantial lymphocyte recirculation through bone marrow. These observations suggest that organ-specific adhesion receptor usage in mature lymphocyte recirculation is not as rigidly adhered to as previously considered, and that the same basic sets of adhesion receptors are used in both lymphocyte homing and inflammatory responses.

Activated T cells enter rat lymph nodes and Peyer's patches via high endothelial venules: survival by tissue-specific proliferation and preferential exit of CD8+ T cell progeny

Activated T cells reach the lymph nodes via afferent lymphatics but it is unknown to what extent they also enter them directly via high endothelial venules (HEV). Little is known about the mechanism mediating the proliferation of activated T cells within lymphoid tissues in vivo or the subsequent fate of the progeny. Therefore, we stimulated rat T cells via TCR and CD28 in vitro and after injection identified them in the blood and the HEV of lymphoid organs at several time points. In addition, the proliferation of these cells was studied after entering different lymphoid organs. Our results show that, firstly, activated T cells continuously enter lymph nodes and Peyer's patches directly via HEV. Second, they proliferate within lymphoid organs, the rate significantly depending on the microenvironment. Third, mainly CD8+ progeny are able to leave the tissues and re-enter the blood. Thus, the distribution of activated T cells circulating through the body can be regulated during entry, but also within the tissue by influencing their proliferation and subsequent release.

Mission-driven marketing: a rural example

Marketing receives little attention in the academic healthcare management literature, possibly because it is associated with pursuit of profit rather than community benefit. However, a marketing perspective can be applied to the pursuit of the traditional missions of healthcare delivery organizations. Mission-oriented market selection criteria could include characteristics such as relevance to mission, underserved or vulnerable population status, resistance to care, limited resources, and low accessibility. A survey conducted in a rural county is used to demonstrate ways that underserved market segments can be identified and targeted. In the market surveyed, men used less medical care than women; depressed people and those with low levels of education used less medical care than people without these characteristics. Consumers were more likely to defer care because of cost if they lacked health insurance coverage, were female, were under age 55, had fair health status, were depressed, and were chronically ill. Marketing strategies worthy of consideration relate to price (e.g., free care, coupons and sales for eligible individuals), distribution (e.g., visiting nurses, malls and fairs, occupational medicine programs), product (e.g., satisfaction, waiting time, attractiveness, assertive follow-up), and promotion (education about insurance benefits, facilitating development of regular sources of care, health education).

Dendritic cells prevent CD95 mediated T lymphocyte death through costimulatory signals

T cell apoptosis is a mechanism regulating T cell homeostasis. Prolonged stimulation renders T cells susceptible to activation induced cell death (AICD), a process mediated through CD95 (Apo-1/Fas). While under some circumstances AICD can be prevented, little is known about molecules involved. Here, we wanted to assess whether dendritic cells (DC) have the capacity to prevent CD95-dependent AICD. T cells activated with PHA/PMA or anti-CD3 monoclonal antibody (mAb) were cocultured with increasing amounts of DC. While spontaneous T cell apoptosis amounted to 25%, the presence of an agonistic anti-CD95 antibody increased cell death to 64%. Addition of scalar amounts of DC prevented T cell apoptosis in a dose dependent fashion, where coculture of 10(5) DC/ml with 10(6) T cells/ml reduced apoptosis almost to baseline level (33%). Further addition of an anti-CD58 antibody partially abolished this protective effect. This was even more pronounced if anti-CD80 and anti-CD86 antibodies were added. Our findings suggest that dendritic cells are able to rescue T cells from AICD, with CD58 ligation playing a key role.

Increased expression of activation markers and adhesion molecules on lung T-cells compared with blood in the normal rat

Lymphocytes play an important role in many lung diseases and are routinely accessible by bronchoalveolar lavage (BAL). Lymphocytes from the BAL (BAL pool) have a different subset composition to those from peripheral blood, consisting mainly of activated T-cells. The aim of this study was to examine whether preferential migration of activated T-cells to the bronchoalveolar space or factors of the specific microenvironment mediate this phenomenon. The expression of adhesion molecules and cellular activation markers (intercellular adhesion molecule-1, leukocyte function-associated antigen-1, CD2, CD44, interleukin-2 receptor and L-selectin) was studied on T- and B-cells not only in the BAL and peripheral blood (blood pool), but also in the compartments in between, such as the lung vascular perfusate (marginal pool) and the lung interstitium (interstitial pool), with the experiments being performed simultaneously in the same animals. Low levels of adhesion molecule expression were observed on T-cells in the blood and marginal pool, medium levels in the lung interstitium and the highest levels in the BAL. "Memory" (CD45R(low)) and "naive" (CD45R(high)) T-cells in the lung compartments showed a higher expression of adhesion molecules compared with blood. However, the predominating CD45R(low) T-cells showed a significantly higher expression than the CD45R(high) cells, indicating that CD4+ CD45R(high) T-cells had changed their phenotype to CD45R(low). In conclusion, a high level of expression of leukocyte function associated antigen-1 and intracellular adhesion molecule-1 on the bronchoalveolar lavage and interstitial T-cells is more likely to be the result of local, lung-specific induction than a prerequisite for migration into the bronchoalveolar space.

FcgammaRIII (CD16)-deficient mice show IgG isotype-dependent protection to experimental autoimmune hemolytic anemia

In autoimmune hemolytic anemia (AIHA), there is accumulating evidence for an involvement of FcgammaR expressed by phagocytic effector cells, but demonstration of a causal relationship between individual FcgammaRs and IgG isotypes for disease development is lacking. Although the relevance of IgG isotypes to human AIHA is limited, we could show a clear IgG isotype dependency in murine AIHA using pathogenic IgG1 (105-2H) and IgG2a (34-3C) autoreactive anti-red blood cell antibodies in mice defective for FcgammaRIII, and comparing the clinical outcome to those in wild-type mice. FcgammaRIII-deficient mice were completely resistent to the pathogenic effects of 105-2H monoclonal antibody, as shown by a lack of IgG1-mediated erythrophagocytosis in vitro and in vivo. In addition, the IgG2a response by 34-3C induced a less severe but persistent AIHA in FcgammaRIII knock-out mice, as documented by a decrease in hematocrit. Blocking studies indicated that the residual anemic phenotype induced by 34-3C in the absence of FcgammaRIII reflects an activation of FcgammaRI that is normally coexpressed with FcgammaRIII on macrophages. Together these results show that the pathogenesis of AIHA through IgG1-dependent erythrophagocytosis is exclusively mediated by FcgammaRIII and further suggest that FcgammaRI, in addition to FcgammaRIII, contributes to this autoimmune disease when other IgG isotypes such as IgG2a are involved.

Effects of the anti-CD2 mAb OX34 on in vivo proliferation

In vitro studies indicate that CD2 plays an important role in the intestinal immune system with regard to T cell proliferation and T helper 2 differentiation. We asked whether anti-CD2 mAb induces T-cell proliferation in vivo. Rats received anti-CD2 mAb OX34 or control mAb over 3 days. Before exsanguination BrdU was injected. Lymphatic organs were processed for two-color immunohistology. OX34 depleted CD4+ but not CD8+ T cells in all organs. Remaining CD4+ T cells proliferated in the periarteriolar lymphocyte sheets. Surprisingly, OX34 led to strong proliferation of splenocytes in the red pulp. These cells were negative for markers of T cells, B cells, NK cells, macrophages, and myeloid cells. Taken together, the anti-CD2 mAb OX34 leads to proliferation of an as-yet-unidentified cell type in the red pulp of the spleen but not to proliferation of T cells.

Behaviorally conditioned immunosuppression using cyclosporine A: central nervous system reduces IL-2 production via splenic innervation

Bi-directional interactions between the central nervous system (CNS) and immune system are demonstrated by the modification of immune function using behavioral conditioning. However, the mechanisms by which the CNS achieves conditioned immunomodulation are still in question. Here, we report that the immunosuppressive effects of cyclosporine A (CsA) can be behaviorally conditioned in rats using saccharin as a gustatory conditioned stimulus. The conditioned effects were compared to control groups that received CsA paired with water (sham-conditioned), CsA injection on test days (CsA-treated), and unhandled rats (untreated). In conditioned animals, the mitogen-induced lymphocyte proliferation in the spleen is significantly suppressed, and the survival time of heterotopic heart allografts prolonged. These effects are paralleled by conditioned inhibition of IL-2 and IFN-gamma synthesis by splenocytes. Furthermore, the CNS-induced immunosuppression is mediated neuronally and not via the blood, since the conditioned reduction of proliferation and cytokine production is completely abrogated after surgical denervation of the spleen. Thus, during conditioning, the CNS learns to reinstate at demand a CsA-like immunosuppression via splenic innervation. This might be used as a supportive therapy for controlling immune functions.

Regeneration of implanted splenic tissue in the rat: re-innervation is host age-dependent and necessary for tissue development

The loss of spleen may lead to fatal bacterial infections. To prevent this, splenic autotransplantation has been performed in humans and experimental animals. However, there is still controversy about the protective function of this procedure. Since innervation plays an important role in splenic function, we investigated whether splenic regenerates are re-innervated, and whether this depends on the donor and host age. Splenic tissue (30 mg) was implanted into the greater omentum of either young (2 days) or old (12 months) rats, from either young or old syngeneic animals. After 3 months of regeneration, the weight of the regenerates was determined, PGP+ nerve fibers were revealed by immunohistology, and subdivided into nerve fibers of sympathetic (TH+, NPY+) or sensory (SP+, CGRP+) origin. In addition, proliferating (Ki-67 proliferation antigen+) and apoptotic cells (TUNEL technique+) were likewise investigated. No innervation of splenic regenerates was observed after implantation into old hosts, correlating with poorly developed splenic compartments. In contrast, almost normal re-innervation occurred in young hosts after implantation of both young and old splenic tissue. These regenerates showed well-developed splenic compartments and a normal number and tissue distribution of proliferating and apoptotic cells. However, after the implantation of young tissue, the final size of splenic regenerates was three times larger (140 +/- 30 vs. 40 +/- 10 mg). Thus, re-innervation of splenic implants is necessary for their subsequent development. It is determined by host age, whereas the final size of the splenic regenerates is regulated by donor age-dependent factors. This model is useful for studying both the process leading to initial innervation and the consequences of this innervation.

Behaviorally conditioned effects of Cyclosporine A on the immune system of rats: specific alterations of blood leukocyte numbers and decrease of granulocyte function

Immunosuppression induced by Cyclosporine A (CsA) can be behaviorally conditioned. It is unknown, however, whether a taste aversion paradigm using CsA as an unconditioned stimulus (UCS) induces alterations of blood leukocyte numbers and function. Results obtained by three-colour flow cytometry and granulocyte chemiluminescence response demonstrate that in conditioned rats, absolute numbers of lymphocyte subsets, including B, CD8+ T cells and CD4+ naive and memory T cells, and granulocyte numbers and function were significantly decreased. In contrast to the conditioned response, CsA treatment alone increased lymphocyte numbers and did not affect granulocyte function. Thus, our data demonstrate that behaviorally conditioned CsA effects can be monitored in the blood. In addition, results indicate that the CNS mediates the behaviorally conditioned immunosuppression by reducing the availability and function of granulocytes and lymphocytes.

Cyclosporine A affects open field behavior in DA rats

Since the introduction of Cyclosporine A (CsA) for immunosuppression in solid-organ transplantation, the rate of allograft rejection has decreased substantially. However, treatment with CsA induces neuropsychological complications in patients, including affective disorders such as anxiety, disorientation, depression, aggression, paranoia, and apathy. These CsA-induced affective side effects cannot be extensively studied in humans. Therefore, this study investigates the effects of intraperitoneal CsA (20 mg/kg) injections on the open-field behavior of male Dark Agouti (DA) rats 1, 6, 12, and 23 h after drug administration on 3 consecutive days. CsA induced an increase in emotionality in DA rats 6 h after injection, reflected by decreased ambulatory activity in the open field and increased defecation. In addition, a decrease in rearing activity was observed 12 h after CsA administration. These behavioral alterations are discussed in the view of changes in cytokine profiles induced by CsA.

Retroviral interleukin-7 gene transfer into human dendritic cells enhances T cell activation

Tumor vaccination with dendritic cells (DC) presenting tumor antigens to T cells is a promising approach in immunotherapy. The aim of this study was to enhance T cell stimulatory ability of human DC by retroviral expression of the interleukin-7 (IL-7) gene. IL-7 has been shown to provide a potent costimulatory signal for the proliferation of T cells and the generation of cytotoxic T cells (CTL). DC were generated from human peripheral blood mononuclear cells (PBMC). DC were analyzed by light- and electron-microscopy, immunophenotype (CD1a+, CD14-, CD80+, CD86+, HLA-DR+) and functional assays. According to these criteria, 75-85% of the cells were DC. The cells did not produce measurable amounts of IL-7 spontaneously nor did they express the IL-7 receptor. A retroviral IL-7 expression vector was constructed. Retroviral infection was performed with either the LXSN-hIL-7 vector of its variant LXSN. Using the LXSN-hIL-7 vector, IL-7 production of 2296 pg/10(6) cells/24 h could be achieved on average. Transduction of DC was confirmed by RT-PCR in a CD1a-enriched cell fraction. Transduction efficiency by a control virus coding for beta-galactosidase was about 30%. In autologous mixed lymphocyte reaction (MLR), IL-7 transduced DC augmented T cell proliferation by a factor of two compared with unmodified or mock-transfected DC, and in allogeneic MLR there was a 2.7-fold increase in T cell proliferation. The increase in T cell proliferation could be correlated to IL-7 secretion by DC. Dendritic cells that have been simultaneously peptide-loaded and gene-modified to secrete IL-7 are a potential tool to amplify activation of tumor-specific T cells.

Conditioned taste aversion produced by cyclosporine A: concomitant reduction in lymphoid organ weight and splenocyte proliferation

The classical conditioning of immune parameters is commonly conducted within a conditioned taste aversion (CTA) paradigm. In this study, the immunosuppressive drug cyclosporine A (CsA) was investigated for its ability to produce both taste aversion to a novel stimulus and conditioned alterations in immune functioning. The paradigm comprised the pairing of a 0.2% saccharin solution (the conditioned stimulus; CS) with an intraperitoneal injection of 20 mg/kg CsA (the unconditioned stimulus; UCS). Upon saccharin re-presentation, a marked reduction in fluid consumption was observed, indicating aversion to the novel substance (=CTA). By using a single CsA/saccharin pairing the CTA lasted for one CS representation. However, by implementing three pairings, this effect could be extended for up to seven representations. No noticeable difference was recorded by adjusting the saccharin representation from every consecutive day to every second day. The most effective paradigm in creating CTA was subsequently investigated for its effectiveness in producing conditioned immune alterations. Animals were killed on the day of the third CS re-presentation, and immune functions assessed. Conditioned animals displayed a significant reduction in thymus and spleen weights. Effects on the spleen were further investigated, revealing a significantly reduced proliferative ability of isolated splenocytes to concanavalin A. These results demonstrate that the physiological effects produced by CsA are sufficiently salient to elicit CTA. Furthermore, the reduction in lymphoid organ weight and splenocyte proliferation induced by CsA are also conditionable using this paradigm.

Initiation and perpetuation of rat adjuvant arthritis is inhibited by the anti-CD2 monoclonal antibody (mAb) OX34

OBJECTIVE

The purpose of this study was to investigate the therapeutic potential of the anti-CD2 mAb OX34 first with regard to bone protection in established rat adjuvant arthritis (AA) and secondly with regard to prevention of AA induction.

METHODS

Established AA was treated with dexamethasone (1 mg/kg body weight) for two days plus OX34 mAb or control mAb over three days (2 mg and then 1 mg) starting at different time points of the disease. For prevention studies animals were injected as above with mAb before induction of AA. Arthritis score (AS), hindpaw thickness, and body weight were blindly measured three times per week. Flow cytometry and hindpaw radiography were performed at the end of the study (day 29).

RESULTS

Treatment of early AA with OX34 mAb combined with dexamethasone but not dexamethasone plus control mAb dramatically suppressed established AA as assessed by AS and hind paw thickness (> 65% and > 80% reduction, respectively; p < 0.05). Most importantly, early treatment in the course of AA almost completely prevented bone destruction in established AA. When given before AA induction OX34 alone prevented the initiation of arthritis compared with controls (AS reduction 83-95%, p < 0.05). In addition, OX34 plus dexamethasone treatment resulted in depletion of CD4+ T cells but not CD8+ T cells. IL2R+ and CD45RC- ('memory') T cells were significantly reduced.

CONCLUSIONS

Anti-CD2 mAb treatment prevents AA induction confirming the role of CD4+ T cells in the induction phase of AA. In addition, early OX34 plus dexamethasone treatment resulted in pronounced clinical improvement and joint protection. OX34 treatment therefore inhibits the initiation and the perpetuation of rat AA.