Evidence for mouse Th1- and Th2-like helper T cells in vivo. Selective reduction of Th1-like cells after total lymphoid irradiation

The Characterization of the Th1/Th2 Ratio in Moderate-Severe Alzheimer's Disease Patients and Its Response to an Aloe Polymannose-Based Dietary Supplement

BACKGROUND

Alzheimer's disease (AD) is a leading killer of Americans, imparting a tremendous societal toll. Relationships between immune function and inflammation with cognition are well-established in AD, but the Th1/Th2 ratio of immune function is unknown. Describing the Th1/Th2 ratio and its relationship with cognition may shed light on the disease's clinical context. How the Th1/Th2 ratio responds to dietary supplementation is another unknown question in this population.

OBJECTIVE

The objectives of the study were to: 1) characterize the Th1/Th2 ratio according to IL-2/IL-10, IFN-γ/IL-10, IL-2/IL-4, IFN-γ/IL-4, IL-2/TNF-α, and IFN-γ/TNF-α in subjects with moderate-to-severe AD and in comparison to healthy adults; 2) investigate the effect of an aloe polymannose multinutrient complex (APMC) dietary supplement on the Th1/Th2 ratios over 12 months; and 3) compare the changes in the Th1/Th2 ratios with the changes in cognition from baseline to 12 months.

METHODS

Subjects consumed 2.5 g of the APMC four times per day for 12 months, and they were assessed on cognition and cytokines at baseline and 12 months.

RESULTS

The Th1/Th2 ratios in AD patients were significantly higher than the healthy controls, and five of the six ratios decreased from baseline to 12 months follow-up (other than IL-2/TNF-α). Several significant relationships were noted between the changes in Th1/Th2 ratios with cognitive assessments.

CONCLUSIONS

Our results showed an overall rebalancing of the Th1/Th2 ratio in response to APMC, these changes were related to improved cognition in subjects with moderate-to-severe AD, and the APMC supplement was safely tolerated.

Mechanisms of Normal Tissue Injury From Irradiation

Normal tissue injury from irradiation is an unfortunate consequence of radiotherapy. Technologic improvements have reduced the risk of normal tissue injury; however, toxicity causing treatment breaks or long-term side effects continues to occur in a subset of patients. The molecular events that lead to normal tissue injury are complex and span a variety of biologic processes, including oxidative stress, inflammation, depletion of injured cells, senescence, and elaboration of proinflammatory and profibrogenic cytokines. This article describes selected recent advances in normal tissue radiobiology.

Impairment of the Intrinsic Capability of Th1 Polarization in Irradiated Mice: A Close Look at the Imbalanced Th1/Th2 Response after Irradiation

Two major CD4⁺ T-helper (Th) lineages are Th1 and Th2, and well balanced Th1/Th2 responses are essential for immune function. In previously published studies, it was reported that radiation induces a Th1/Th2 immune imbalance toward a Th2-dominant direction, and this imbalance may contribute to postirradiation immune dysfunction. The polarization of Th cells is driven by the cytokine milieu and controlled by intracellular regulatory pathways that respond to cytokine signaling. It is widely accepted that radiation induces cytokine aberration, however, the precise alterations of cytokines in various tissue environments have been difficult to evaluate. In addition, the effects of radiation on the intrinsic functions of Th cells remain uncharacterized. Therefore, how radiation affects Th1/Th2 balance remains somewhat unclear. To address this, we investigated the changes in the polarization capability of Th cells by isolating them from mice previously exposed to radiation and assessing the cells in an established in vitro Th polarization system. Our novel results demonstrate that prior exposure to radiation led to the persistent aberration of the inherent capability of Th cells to differentiate into Th1 and Th2 lineages. The parallel changes in expression of Th1-specific master transcription factors and the key genes in metabolic reprograming indicated that radiation affects the core components in Th1 polarization. While Th1 differentiation was impaired after irradiation, little adverse effect was observed in Th2 differentiation; both of these findings contribute to the known phenotypes of Th1/Th2 imbalance caused by radiation.

Effect of murine exposure to gamma rays on the interplay between Th1 and Th2 lymphocytes

Gamma radiation radiotherapy is one of the widely used treatments for cancer. There is an accumulating evidence that adaptive immunity is significantly contributes to the efficacy of radiotherapy. This study is carried out to investigate the effect of gamma rays on the interplay between Th1/Th2 response, splenocyte lymphoproliferative response to polyclonal mitogenic activators and lymphocytic capacity to produce IL-12 and IL-10 in mice. Results showed that exposure of intact spleens to different doses of γ-rays (5, 10, 20 Gy) caused spontaneous and dose-dependent immune stimulation manifested by enhanced cell proliferation and elevated IL-12 production with decreased IL-10 release (i.e., Th1 bias). While exposure of splenocytes suspension to different doses of γ-rays (5, 10, 20 Gy) showed activation in splenocytes stimulated by PWM at 5 Gy then a state of conventional immune suppression that is characterized by being dose-dependent and is manifested by decreased cell proliferation and IL-12 release accompanied by increase in IL-10 production (i.e., Th2 bias). In addition, we investigated the exposure of whole murine bodies to different doses of γ-rays and found that the exposure to low dose γ-rays (0.2 Gy) caused a state of immune stimulation terminated by a remarkable tendency for immune suppression. Exposure to 5 or 10 Gy of γ-rays resulted in a state of immune stimulation (Th1 bias), but exposure to 20 Gy showed a standard state of immune suppression (Th2 bias). The results indicated that apparently we can control the immune response by controlling the dose of γ-rays.

Interleukin-12 preserves the cutaneous physical and immunological barrier after radiation exposure

The United States continues to be a prime target for attack by terrorist organizations in which nuclear detonation and dispersal of radiological material are legitimate threats. Such attacks could have devastating consequences to large populations, in the form of radiation injury to various human organ systems. One of these at risk organs is the cutaneous system, which forms both a physical and immunological barrier to the surrounding environment and is particularly sensitive to ionizing radiation. Therefore, increased efforts to develop medical countermeasures for treatment of the deleterious effects of cutaneous radiation exposure are essential. Interleukin-12 (IL-12) was shown to elicit protective effects against radiation injury on radiosensitive systems such as the bone marrow and gastrointestinal tract. In this article, we examined if IL-12 could protect the cutaneous system from a combined radiation injury in the form of sublethal total body irradiation and beta-radiation burn (β-burn) directly to the skin. Combined radiation injury resulted in a breakdown in skin integrity as measured by transepidermal water loss, size of β-burn lesion and an exacerbated loss of surveillant cutaneous dendritic cells. Interestingly, intradermal administration of IL-12 48 h postirradiation reduced transepidermal water loss and burn size, as well as retention of cutaneous dendritic cells. Our data identify IL-12 as a potential mitigator of radiation-induced skin injury and argue for the further development of this cytokine as a radiation countermeasure.

Murine P-glycoprotein deficiency alters intestinal injury repair and blunts lipopolysaccharide-induced radioprotection

P-glycoprotein (P-gp) has been reported to increase stem cell proliferation and regulate apoptosis. Absence of P-gp results in decreased repair of intestinal epithelial cells after chemical injury. To further explore the mechanisms involved in the effects of P-gp on intestinal injury and repair, we used the well-characterized radiation injury model. In this model, injury repair is mediated by production of prostaglandins (PGE(2)) and lipopolysaccharide (LPS) has been shown to confer radioprotection. B6.mdr1a(-/-) mice and wild-type controls were subjected to 12 Gy total body X-ray irradiation and surviving crypts in the proximal jejunum and distal colon were evaluated 3.5 days after irradiation. B6.mdr1a(-/-) mice exhibited normal baseline stem cell proliferation and COX dependent crypt regeneration after irradiation. However, radiation induced apoptosis was increased and LPS-induced radioprotection was blunted in the C57BL6.mdr1a(-/-) distal colon, compared to B6 wild-type controls. The LPS treatment induced gene expression of the radioprotective cytokine IL-1α, in B6 wild-type controls but not in B6.mdr1a(-/-) animals. Lipopolysaccharid-induced radioprotection was absent in IL-1R1(-/-) animals, indicating a role for IL-1α in radioprotection, and demonstrating that P-gp deficiency interferes with IL-1α gene expression in response to systemic exposure to LPS.

Fractionated irradiations lead to chronic allergic airway inflammation through increasing the influx of macrophages

OBJECTIVE

In our previous study, repeated irradiations showed persistent depression of immune response, especially Th1-related immune response. Here, we hypothesized and determined that irradiation may exacerbate development of allergic airway inflammation.

METHODS

C57BL/6 mice were irradiated repeatedly at 1 Gy or 0.5 Gy. At 6 months after irradiation, mice were sensitized and challenged short-term with OVA. Antigen-specific immunoglobulins, the percentages of inflammatory cells, chemokine expression, cytokine levels, and collagen deposition were tested.

RESULTS

In irradiated mice, IgG2a in serum was lower when compared with that of control mice, while IgG1 was significantly higher. Interestingly, the percentages of macrophages in bronchoalveolar lavage fluid (BALF) and the lung of irradiated mice were significantly higher. Conversely, the percentages of neutrophil were significantly lower in BALF of irradiated mice. In the lung of irradiated mice, MCP-1 and IP-10 for attraction of macrophages showed the higher expression level, but KC expression for neutrophils showed no difference. Next, TGF-β1 and IL-17A in BALF were higher in irradiated mice. In addition, phosphorylated-Smad2/3 was increased in irradiated mice. Finally, the deposition of collagen was increased in irradiated mice.

CONCLUSION

Our study showed that fractionated irradiation lead to the chronic allergic airway inflammation through increasing the influx of macrophages and active TGF-β levels.

HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses in fractionated γ-irradiated mice by modulating the IL-12p70-STAT4 signaling pathway

Whole body irradiated mice appear to experience a down-regulation of the helper T (Th)1-like immune response, and maintain a persistent immunological imbalance. In the current study, we evaluated the effect of HemoHIM (an herbal product made from Angelica Radix, Cnidium officinale , and Paeonia japonica cultivated in Korea) to ameliorate the immunological imbalance induce in fractionated γ-irradiated mice. The mice were exposed to γ rays twice a week (0.5 Gy fractions) for a total dose of 5 Gy, and HemoHIM was administrated orally from 1 week before the first irradiation to 1 week before the final analysis. All experiments were performed 4 and 6 months after their first exposure. HemoHIM ameliorated the Th1- and Th2-related immune responses normally occur in irradiated mice with or without dinitrophenylated keyhole limpet hemocyanin immunization. HemoHIM also restored the natural killer cell activities without changing the percentage of natural killer cells in irradiated mice. Furthermore, the administration of HemoHIM prevented the reduction in levels of interleukin-12p70 in irradiated mice. Finally, we found that HemoHIM enhanced the phosphorylation of signal transducer and activator of transcription (STAT) 4 that was reduced in irradiated mice. Our findings suggest that HemoHIM ameliorates the persistent down-regulation of Th1-like immune responses by modulating the IL-12p70/pSTAT4 signaling pathway.

Chronic effects of single and fractionated γ-irradiation on an impairment of Th1-related immune response

PURPOSE

We already reported that levels of interferon (IFN)-γ have been shown to be markedly reduced in mice seven weeks after irradiation, resulting in a T helper (Th) 1/Th2 imbalance. To investigate whether the single or fractionated γ-irradiation induced an immune imbalance, we analysed the Th1-related immune response profile until six months after the fractionated whole-body irradiation.

METHODS AND MATERIALS

Mice were exposed to γ-rays at a fractionated 5 Gy cumulative dose for five weeks. At two, four and six months later from the first exposure, experiments were performed. Cell populations in the spleen, the production of IFN-γ, interleukin (IL)- 4 and IL-12p70, natural killer (NK) cell activity and the expression of IL-12 receptors, signal transducer and activator of transcription (STAT) 4 and suppressors of cytokine signaling (SOCS) 3 were detected.

RESULTS

The IFN-γ was lower in the mice exposed by all irradiation conditions than in normal control mice, but the IL-4 had increased in all the irradiated mice. To investigate Th1 profile, NK cell activity, IL-12p70 level and its receptor expression was confirmed. In all fractionated irradiation groups, the NK cell activity as well as the absolute numbers of NK cells was much decreased. Also, all the irradiated mice showed a lower IL-12p70 level. However, the expression of IL-12 receptor β2 was lower in the irradiated mice except the 0.2 Gy × 10 mice group. The phosphoylated STAT4 was lower in all the irradiated mice. This suppression was associated with an overexpression of SOCS3.

CONCLUSIONS

The fractionated whole-body irradiations of a dose of 5 Gy appear to be the down-regulation of the Th1-like immune response. These changes, in turn, maintain an immunological imbalance that persists in the long term.

Lasting effects of an impairment of Th1-like immune response in γ-irradiated mice: A resemblance between irradiated mice and aged mice

Although one of the several chronic effects of ionizing radiation is aging, there are no experimental data on radiation-induced immunological aging. The most interesting change in aging was a helper T (Th) 1/Th2 imbalance. We investigated chronic effect on immune responses after ionizing radiation and its effects in irradiated mice were compared with those of aged mice. The 2-month-old mice received a whole-body irradiation of 5Gy. At 6months after irradiation, we compared the immune functions of the irradiated mice with those of normal mice of the same age and with those of older. Interferon (IFN)-γ and antigen-specific immunoglobulin (Ig)G2a level were lower in the irradiated mice than in normal mice of same age, showing similar levels to those of old normal mice. In contrast, interleukin (IL)-4 and IL-5 and antigen-specific IgG1 level were increased in irradiated mice when compared with the same aged-normal mice. Next, we investigated the low expression of IL-12p70, IL-12 receptors and IL-18 receptors in irradiated and old mice. Also, the decrease of natural killer cell activity was intensified in the irradiated mice, showing lower than values to those of old mice. Interestingly, in irradiated mice, the absolute numbers and the percentages of natural killer (NK) cells was extremely decreased. But the absolute numbers of Th cells and cytotoxic T (Tc) cells in old mice were significantly decreased. In conclusion, an immunological imbalance by the whole-body irradiation of 5Gy induces to persist in the long term, resulting in the similar results with aging. Our results suggest that the downregulation of the Th1-like immune response shown in old mice rapidly occurred through exposure of ionizing radiation.

Exacerbation of autoimmune thyroiditis by a single low dose of whole-body irradiation in non-obese diabetic-H2h4 mice

PURPOSE

To evaluate how irradiation affects thyroid autoimmunity in mouse models of Hashimoto's thyroiditis and Graves' hyperthyroidism.

MATERIALS AND METHODS

Non-obese diabetic (NOD)-H2(h4) mice spontaneously develop anti-thyroglobulin (Tg) antibodies and thyroiditis when supplied with sodium iodine (NaI) in the drinking water. BALB/c mice develop anti-thyrotropin receptor (TSHR) antibodies and hyperthyroidism following immunization with adenovirus expressing TSHR (Ad-TSHR). Mice were irradiated as follows: A single whole-body irradiation with 0.05, 0.5 or 3 Gy one week before or after the beginning of NaI or immunization with Ad-TSHR, fractionated whole-body irradiations with 0.05 Gy twice a week or 0.5 Gy once a week from one week before NaI or Ad-TSHR immunization, or a single regional irradiation to the thyroid gland with 0.5 Gy one week before NaI. The effect of a single irradiation with 0.05, 0.5 or 3 Gy on splenocytes was also evaluated.

RESULTS

A single whole-body irradiation with 0.5 Gy one week before NaI exacerbated thyroiditis and increased anti-Tg antibody titers in NOD-H2(h4) mice. In contrast, any irradiation protocols employed did not affect incidence of hyperthyroidism or anti-TSHR antibody titers in BALB/c mice. High-dose irradiation increased the relative ratios of effector T cells to regulatory T cells (an indication of enhanced immune status) but kills most of T cells.

CONCLUSIONS

These results indicate that a single whole-body low-dose irradiation with 0.5 Gy exacerbates thyroiditis in NOD-H2(h4) mice, data consistent with some clinical evidence for increased incidence of thyroid autoimmunity by environmental irradiation.

Transplant acceptance following anti-CD4 versus anti-CD40L therapy: evidence for differential maintenance of graft-reactive T cells

Inductive therapy with anti-CD4 or anti-CD40L monoclonal antibodies (mAb) leads to long-term allograft acceptance but the immune parameters responsible for graft maintenance are not well understood. This study employed an adoptive transfer system in which cells from mice bearing long-term cardiac allografts following inductive anti-CD4 or anti-CD40L therapy were transferred into severe combined immunodeficiency (SCID) allograft recipients. SCID recipients of cells from anti-CD4-treated mice (anti-CD4 cells) did not reject allografts while those receiving cells from anti-CD40L-treated mice (anti-CD40L cells) did reject allografts. Carboxyfluorescein succinimidyl ester (CFSE) labeling of transferred cells revealed that this difference was not associated with differential proliferative capacities of these cells in SCID recipients. Like cells from naïve mice, anti-CD40L cells mounted a Th1 response following transfer while anti-CD4 cells mounted a dominant Th2 response. Early (day 10) T-cell priming was detectable in both groups of primary allograft recipients but persisted to day 30 only in recipients treated with anti-CD4 mAb. Thus, anti-CD40L therapy appears to result in graft-reactive T cells with a naïve phenotype while anti-CD4 therapy allows progression to an altered state of differentiation. Additional data herein support the notion that anti-CD40L mAb targets activated, but not memory, cells for removal or functional silencing.

Protective conditioning against GVHD and graft rejection after combined organ and hematopoietic cell transplantation

We have performed combined organ and hematopoietic cell transplantation using a similar conditioning regimen in mice and humans. In the mouse model of MHC-mismatched combined heart and marrow transplantation, we compared conditioning of BALB/c hosts with total lymphoid irradiation (TLI: 10 doses of 240 cGy each) targeted to the spleen, lymph nodes and thymus to conditioning with a single dose of sublethal total body irradiation (TBI; 450 cGy). Conditioning also included three injections of anti-thymocyte serum (ATS), in both groups. C57BL/6 heart grafts, marrow cells and blood mononuclear cells were transplanted 24 h after the completion of irradiation. Blood mononuclear cells were added to the marrow cells to engender severe graft versus host disease (GVHD) that is present after combined organ and hematopoietic cell transplantation in humans given non-myeloablative conditioning. Both TLI and TBI conditioned groups accepted the organ grafts and became stable chimeras. However, the TBI group all died of GVHD during the 100-day observation period. The TLI group survived during the same period without clinical signs of GVHD. These hosts were tolerized to the donor organ grafts, since third party grafts were rejected rapidly when transplanted after 100 days. When NK T-cell-deficient CD1d(-/-) BALB/c hosts were used instead of wild-type hosts in the TLI/ATS conditioned group, then all hosts survived but all rejected the organ grafts and almost all failed to develop stable chimerism. None developed GVHD. Since host NK T cells were required for graft acceptance and NK T cells are activated after recognition of CD1d on antigen presenting cells, we compared heart and marrow graft survival from wild-type versus CD1d(-/-) donors after transplantation to TLI and ATS conditioned wild-type hosts. Whereas marrow and heart grafts from wild-type donors were accepted, almost all grafts from CD1d donors were rejected. Grafts from control Jalpha18(-/-) donors that were NK T cell deficient but expressed CD1d were all accepted. The results indicate that host NK T cells facilitate graft acceptance by recognizing CD1d on donor cells. We applied the TLI conditioning regimen using 10 doses of 80 cGy each and 5 doses of rabbit ATG to human recipients of HLA-matched G-CSF "mobilized" blood mononuclear cell transplants for the treatment of leukemia and lymphoma [R. Lowsky, T. Takahashi, Y.P. Liu, et al., Protective conditioning for acute graft-versus-host disease. N. Engl. J. Med. 353 (2005) 1321-1331.]. Currently more than 100 transplants have been performed, and the incidence of acute GVHD has been about 4% when both MRD and MUD transplants are combined. Almost all recipients became complete chimeras after receiving grafts that contained 2-3x10(8) CD3(+) T cells/kg. In further studies, we applied the same TLI and ATG conditioning regimen to combined kidney and G-CSF "mobilized" blood stem cell transplantation from HLA-matched sibling donors. The hematopoietic grafts in the latter protocol were selected CD34(+) cells with 1x10(6) CD3(+) T cells/kg added back to the hematopoietic cells. Preliminary results indicate that stable mixed chimerism can be achieved using this protocol allowing for complete immunosuppressive drug withdrawal without GVHD or subsequent rejection episodes. Thus, conditioning with TLI based regimens can simultaneously protect against organ graft rejection and GVHD. Levels of chimerism are dependent upon the content of donor T cells in the hematopoietic graft.

Pathogenesis and immune responses in gnotobiotic calves after infection with the genogroup II.4-HS66 strain of human norovirus

We previously characterized the pathogenesis of two host-specific bovine enteric caliciviruses (BEC), the GIII.2 norovirus (NoV) strain CV186-OH and the phylogenetically unassigned NB strain, in gnotobiotic (Gn) calves. In this study we evaluated the Gn calf as an alternative animal model to study the pathogenesis and host immune responses to the human norovirus (HuNoV) strain GII.4-HS66. The HuNoV HS66 strain caused diarrhea (five/five calves) and intestinal lesions (one/two calves tested) in the proximal small intestine (duodenum and jejunum) of Gn calves, with lesions similar to, but less severe than, those described for the Newbury agent 2 (NA-2) and NB BEC. Viral capsid antigen was also detected in the jejunum of the proximal small intestine of one of two calves tested by immunohistochemistry. All inoculated calves shed virus in feces (five/five calves), and one/five had viremia. Antibodies and cytokine (proinflammatory, tumor necrosis factor alpha [TNF-alpha]; Th1, interleukin-12 [IL-12] and gamma interferon [IFN-gamma]; Th2, IL-4; Th2/T-regulatory, IL-10) profiles were determined in serum, feces, and intestinal contents (IC) of the HuNoV-HS66-inoculated calves (n = 5) and controls (n = 4) by enzyme-linked immunosorbent assay in the acute (postinoculation day 3 [PID 3]) and convalescent (PID 28) stages of infection. The HuNoV-HS66-specific antibody and cytokine-secreting cells (CSCs) were quantitated by ELISPOT in mononuclear cells of local and systemic tissues at PID 28. Sixty-seven percent of the HuNoV-HS66-inoculated calves seroconverted, and 100% coproconverted with immunoglobulin A (IgA) and/or IgG antibodies to HuNoV-HS66, at low titers. The highest numbers of antibody-secreting cells (ASC), both IgA and IgG, were detected locally in intestine, but systemic IgA and IgG ASC responses also occurred in the HuNoV-HS66-inoculated calves. In serum, HuNoV-HS66 induced higher peaks of TNF-alpha and IFN-gamma at PIDs 2, 7, and 10; of IL-4 and IL-10 at PID 4; and of IL-12 at PIDs 7 and 10, compared to controls. In feces, cytokines increased earlier (PID 1) than in serum and TNF-alpha and IL-10 were elevated acutely in the IC of the HS66-inoculated calves. Compared to controls, at PID 28 higher numbers of IFN-gamma and TNF-alpha CSCs were detected in mesenteric lymph nodes (MLN) or spleen and Th2 (IL-4) CSCs were elevated in intestine; IL-10 CSCs were highest in spleen. Our study provides new data confirming HuNoV-HS66 replication and enteropathogenicity in Gn calves and reveals important and comprehensive aspects of the host's local (intestine and MLN) and systemic (spleen and blood) immune responses to HuNoV-HS66.

Impairment of natural killer (NK) cells is an important factor in a weak Th1-like response in irradiated mice

In whole-body-irradiated (WBI) mice, levels of the canonical Th1 cytokine IFN-gamma (IFNG) have been shown to be markedly reduced, resulting in a Th1/Th2 imbalance. In this study, the influence of natural killer (NK) cells on the balance of this Th1/Th2 immune response was evaluated in WBI mice. Although NK cells are one of the types of cells that secreteIFN-gamma, NK cell activity tends to be minimal, even at 7 weeks after irradiation. In NK cell-depleted mice, the levels of Th1-related cytokines were lower than those of the control mice and were correlated with lower IgG2a production and elevated IgE and IgG1 production. These results indicated that NK cells have a crucial role in the final differentiation of Th cells into Th1 cells. The impairment of NK cells in the WBI mice was confirmed by the observation that NK cells from the WBI mice induced a decrease in the generation of IFN-gamma by the NK cell-depleted spleen lymphocytes from normal mice. Also, the WBI mice that received NK cells obtained from the normal mice generated more IgG2a, IL12 and IFN-gamma. Our results indicate that the impairment of NK cells is an important factor in the reduced Th1-like response in irradiated mice.

The NK1.1+T cells alive in irradiated mice play an important role in a Th1/Th2 balance

PURPOSE

Ionizing radiation is known to reduce the helper T (Th) 1 like function, resulting in a Th1/Th2 imbalance. We studied whether NK1.1+T cells which were the most resistant against gamma-irradiation impact on the imbalanced immune response after irradiation.

MATERIALS AND METHODS

C57BL/6 mice received a whole-body gamma-irradiation (WBI) of 4 Gy. The primary T cells were separated by magnetic cell sorter (MACS) using the anti-CD90.2 antibody. The apoptotic cells were detected by propidium iodide (PI) staining. To determine the Th1 and Th2 cell functions, the production of interferon (IFN)-gamma and interleukin (IL)-4 were analysed by a reverse transcriptase-polymerase chain reaction (RT-PCR) and an enzyme linked immunosorbent assay (ELISA). NK1.1+T cells were detected by flow cytometry. For depletion of the NK1.1+T cells in the WBI mice, anti-asialo GM1 antiserum was injected.

RESULTS

The CD90.2 positive cells of the WBI mice produced significantly more Th2 type cytokines and also produced Th1 type cytokines at a not lower level than normal mice, and contained a higher absolute number of NK1.1+T cells. Also, the proportion of the NK1.1+T cells increased in the WBI mice. We found that the NK1.1+T cells were resistant to radiation-induced apoptosis in comparison with the conventional T cells. The depletion of NK1.1+T cells in WBI mice resulted in higher production of IgE and IL-4 and lower secretion of IL-12p70.

CONCLUSION

Our findings revealed that NK1.1+T cells that survive at an early stage after irradiation play an important role in the balance of the immune responses at a late stage after irradiation.

Repeated irradiations with gamma-rays at a Dose of 0.5 Gy may exacerbate asthma

We previously showed that 0.5 Gy whole-body gamma-ray irradiation with a single or small number of repeated exposures inhibits tumor growth in mice, via elevation of the IFN-gamma/IL-4 ratio concomitantly with a decrease in the percentage of B cells. Here we examined whether repeated 0.5 Gy gamma-rays irradiation can improve asthma in an OVA-induced asthmatic mouse model. We found that repeated irradiation (10 times) with 0.5 Gy of gamma-rays significantly increased total IgE in comparison with the disease-control group. The levels of IL-4 and IL-5 were also significantly higher in the gamma-ray-irradiated group, while that of IFN-gamma was significantly lower, resulting in a further decrease of the IFN-gamma/IL-4 ratio from the normal value. These results indicate that the repeated irradiation with gamma-rays may exacerbate asthma, and may have opposite effects on different immune reactions unlike the irradiation with a single or small number of repeated exposures.

Treating Crohn's disease by inducing T lymphocyte apoptosis

Apoptosis is one of the most important regulatory mechanisms in immunological homeostasis. Disturbances in the apoptotic pathways lead to autoimmune disease. Crohn's disease is a chronic inflammatory bowel disease of unknown origin, which seems to be mediated by excessive T cell-mediated immunity. Recently, disturbances in apoptotic pathways of lamina propria T lymphocytes of patients with Crohn's disease have been identified. In the uninflamed, normal intestinal mucosa, lamina propria (LP) T cells are susceptible to activation-induced cell death, but these cells show a resistance to apoptosis based on several disturbances compared to controls. Recently, intriguing data were published using cytokine-targeted therapy (anti-IL12, anti-IL6 receptor, anti-TNF). Actually, these medications restored mucosal immunological imbalance by inducing apoptosis of the LP T cells and seemed to be beneficial in models of Crohn's disease. In this review, mechanisms of immunological homeostasis will be discussed. We will also discuss the fascinating new results of cytokine-targeted therapy in animal models of Crohn's disease and the effects of these drugs in patients with Crohn's disease.

Predominance of NK1.1+TCR alpha beta+ or DX5+TCR alpha beta+ T cells in mice conditioned with fractionated lymphoid irradiation protects against graft-versus-host disease: "natural suppressor" cells

We developed a nonmyeloablative host conditioning regimen in a mouse model of MHC-mismatched bone marrow transplantation that not only reduces radiation toxicity, but also protects against graft-vs-host disease. The regimen of fractionated irradiation directed to the lymphoid tissues and depletive anti-T cell Abs results in a marked change in the residual host T cells, such that NK1.1+ or DX5+asialo-GM1+ T cells become the predominant T cell subset in the lymphoid tissues of C57BL/6 and BALB/c mice, respectively. The latter "natural suppressor" T cells protect hosts from graft-vs-host disease after the infusion of allogeneic bone marrow and peripheral blood cells that ordinarily kill hosts conditioned with sublethal or lethal total body irradiation. Protected hosts become stable mixed chimeras, but fail to show the early expansion and infiltration of donor T cells in the gut, liver, and blood associated with host tissue injury. Cytokine secretion and adoptive transfer studies using wild-type and IL-4(-/-) mice showed that protection afforded by NK1.1+ and DX5+asialo-GM1+ T cells derived from either donors or hosts conditioned with lymphoid irradiation is dependent on their secretion of high levels of IL-4.

T-cell responses to mitogens in atomic bomb survivors: a decreased capacity to produce interleukin 2 characterizes the T cells of heavily irradiated individuals

Significant decreases in the fraction of lymphocytes that are CD4(+) and increases in serum levels of some classes of immunoglobulin have been reported to occur in atomic bomb (A-bomb) survivors and in victims of the Chernobyl nuclear plant accident. To investigate the long-term effects of nuclear radiation on cellular immunity in more detail, we used limiting dilution assays with peripheral blood mononuclear cell preparations to analyze the T-cell responses of 251 A-bomb survivors exposed to less than 0.005 Gy and 159 survivors exposed to more than 1.5 Gy. The percentages of CD2-positive cells that were capable of proliferating in response to phytohemagglutinin (PHA) in the presence of exogenous interleukin 2 (IL2) did not differ substantially between distally exposed and more heavily exposed survivors. The heavily exposed survivors appeared to possess fewer T cells that were capable of proliferating in response to concanavalin A (Con A) or of producing interleukin 2. Assuming that CD4 T cells were the ones primarily responsible for producing IL2 in response to Con A, we were able to estimate how many cells in any given CD4 T-cell population were actually producing IL2. The results indicated that peripheral blood samples from heavily exposed survivors contained significantly fewer IL2-producing CD4 T cells than did similar samples from distally exposed survivors, indicating that significant exposure to A-bomb radiation may have a long-lasting negative effect on the capacity of CD4 T-cell populations to produce IL2.

Cyclosporine facilitates chimeric and inhibits nonchimeric tolerance after posttransplant total lymphoid irradiation

BACKGROUND

Previous studies showed that Lewis rats given posttransplant total lymphoid irradiation, antithymocyte globulin, and a single infusion of ACI peripheral blood or bone marrow cells develop tolerance to ACI heart allografts.

METHODS

To determine the effects of cyclosporine on these tolerance induction protocols, groups of Lewis hosts, given either ACI blood or marrow infusions, were given a 60-day course of daily cyclosporine immediately after the cell infusion.

RESULTS

Cyclosporine treatment was associated with uniform graft rejection in the groups given an ACI blood transfusion, and was associated with uniform graft acceptance in the groups given an ACI bone marrow infusion. Studies of donor-type T and B cell chimerism in the host blood showed that cyclosporine facilitated chimerism in the hosts given ACI bone marrow cells, and stable chimerism over a 300-day observation period was predicted by detectable chimerism by day 30. None of the hosts given ACI blood cells developed chimerism.

CONCLUSION

Cyclosporine facilitated long-term graft acceptance in a tolerization protocol that induced mixed chimerism, but prevented long-term graft acceptance in a tolerization protocol that did not induce chimerism.

Systemic mycobacterial infection inhibits antigen-specific immunoglobulin E production, bronchial mucus production and eosinophilic inflammation induced by allergen

As the burden of infectious diseases becomes reduced in many countries, a remarkable increase in the incidence of allergies has occurred. The basis for the rise in atopic disorders as a correlate of the decline in infectious diseases has not been defined. In the present study, we tested experimentally whether prior systemic infection with Mycobacterium bovis bacillus Calmette Guérin (BCG) had any effect on ovalbumin (OVA) Al(OH)3 (alum)-induced immunoglobulin E (IgE) production, airway mucus production and eosinophilic inflammation. The data showed that allergen-specific IgE production and OVA-induced eosinophilia and goblet cell development were significantly inhibited by prior infection with BCG. Correspondingly, following immunization with OVA alum, BCG-infected mice exhibited significantly higher levels of allergen-driven interferon-gamma (IFN-gamma) production than the mice without infection. The ratio of IFN-gamma: interleukin (IL)-4 production was higher in OVA-sensitized mice with prior BCG infection than in those without infection. The abrogation of OVA-induced mucus production and pulmonary eosinophilia in BCG-infected mice correlated with significantly decreased IL-5 production and increased IFN-gamma and IL-12 production. These data provide direct evidence that intracellular bacterial infection (i.e. BCG) can inhibit antigen-specific IgE and airway reactivity induced by environmental allergen. Furthermore, the results suggest that changes in cytokine-producing patterns of T lymphocytes and other cells may be the mechanism by which infections influence allergies.

Monocyte-derived dendritic cell precursors facilitate tolerance to heart allografts after total lymphoid irradiation

BACKGROUND

Previous studies have shown that posttransplant total lymphoid irradiation, anti-thymocyte globulin, and an intravenous donor blood cell infusion induce tolerance to ACI heart allografts in Lewis rat hosts.

METHODS

In the current study, fresh ACI monocytes and dendritic cell precursors, derived from short-term culture of the latter cells in granulocyte macrophage colony-stimulating factor, were tested for their capacity to prolong heart allograft survival in this model.

RESULTS

The experimental results show that significant prolongation of graft survival was achieved after injection of the fresh donor monocytes or 2-day or 6-day cultured cells. The 2-day cultured cells were most effective, and more than 60% of hosts maintained graft survival for more than 160 days. Ten-day cultured cells and fresh splenic dendritic cells failed to prolong graft survival. Studies of cell surface markers showed that the 2-day cultured cells had up-regulated class II major histocompatibility complex and CD80, but not CD86 molecules. On the other hand, the 10-day cultured cells and splenic dendritic cells showed intense expression of all three markers. The latter cells stimulated vigorous proliferative and cell-mediated lympholysis responses in the mixed leukocyte reaction, but the fresh and 2-day cultured cells were weak stimulators.

CONCLUSION

The intravenous injection of donor dendritic cell precursors derived from blood monocytes facilitates long-term acceptance of heart allografts.

The role of neutralizing antibody and T-helper subtypes in protection and pathogenesis of vaccinated mice following ocular HSV-1 challenge

In order to determine the possible correlation of specific immune responses with protection against mortality and ocular disease following ocular herpes simplex virus type 1 (HSV-1) challenge, BALB/c mice were vaccinated with different doses and regimens of baculovirus-expressed gD. Neutralizing antibody, virus titres in the eyes, corneal scarring, and survival were measured. In addition, infiltration into the cornea of CD4+ T cells and cells containing the lymphokines interleukin-2 (IL-2), IL-4, IL-6 and tumour necrosis factor-alpha (TNF-alpha) were monitored on days 3, 7, 10, 14 and 21 post-challenge by immunocytochemistry. The vaccination regimens used induced varying degrees of immune responses and protection upon ocular challenge with HSV-1. Our results suggest that neutralizing antibody was the most important immune response in protecting mice against lethal ocular challenge and corneal scarring. TNF-alpha and IL-2 were not crucial in terms of survival and corneal scarring, since gD1 (one vaccination with 1 microg of gD) and gD0.1 (one vaccination with 0.1 microg of gD), both of which provided high levels of protection, showed no TNF-alpha or IL-2 expression. However, TNF-alpha and IL-2 were crucial in terms of virus clearance from the eyes, since gD3 (three vaccinations with 1 microg of gD), which had less virus in their eyes, had high numbers of TNF-alpha and IL-2 infiltrates. Finally, mock-vaccinated mice were not protected from death and corneal disease following HSV-1 challenge. Eyes of mock-vaccinated mice had little or no TNF-alpha or IL-2 responses and the strongest IL-4 and IL-6 responses.

Donor blood monocytes but not T or B cells facilitate long-term allograft survival after total lymphoid irradiation

BACKGROUND

Previous studies showed that a combination of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte globulin (ATG), and a single donor blood transfusion induced tolerance to ACI heart allografts in Lewis rats. All three modalities were required to achieve tolerance. The objective of the current study was to determine the subset(s) of cells in the donor blood that facilitated long-term allograft survival.

METHODS

Lewis hosts received TLI, ATG, and donor cell infusion after heart transplantation. Graft survival, mixed leukocyte reaction (MLR), and intragraft cytokine mRNA were studied.

RESULTS

The intravenous injection of 25 x 10(6) ACI peripheral blood mononuclear cells (PBMC) significantly prolonged graft survival as compared with that of Lewis hosts given TLI and ATG alone. Injection of highly enriched blood T cells or splenic B cells adjusted for the number contained in 25 x 10(6) PBMC failed to induce significant graft prolongation. Unexpectedly, depletion of monocytes (CD11b+ cells) from PBMC resulted in the loss of graft prolongation activity. Enriched populations of monocytes obtained by plastic adherence were more efficient in prolonging graft survival than PBMC on a per cell basis. Hosts with long-term grafts (>100-day survival) showed evidence of immune deviation, because the MLR to ACI stimulator cells was vigorous, but secretion of interferon-gamma in the MLR was markedly reduced. In situ hybridization studies of long-term grafts showed markedly reduced levels of interferon-gamma mRNA as compared with rejecting grafts.

CONCLUSION

Infusion of donor monocytes facilitated graft prolongation via immune deviation.

Glutathione levels in antigen-presenting cells modulate Th1 versus Th2 response patterns

Current thinking attributes the balance between T helper 1 (Th1) and Th2 cytokine response patterns in immune responses to the nature of the antigen, the genetic composition of the host, and the cytokines involved in the early interaction between T cells and antigen-presenting cells. Here we introduce glutathione, a tripeptide that regulates intracellular redox and other aspects of cell physiology, as a key regulatory element in this process. By using three different methods to deplete glutathione from T cell receptor transgenic and conventional mice and studying in vivo and/or in vitro responses to three distinct antigens, we show that glutathione levels in antigen-presenting cells determine whether Th1 or Th2 response patterns predominate. These findings present new insights into immune response alterations in HIV and other diseases. Further, they potentially offer an explanation for the well known differences in immune responses in "Th1" and "Th2" mouse strains.

Modulation of T-helper cell populations: potential mechanisms of respiratory hypersensitivity and immune suppression

Information presented at this symposium indicates that modulation of Th cell responses is one means by which xenobiotics may cause immunotoxicity. A shift from Th1 to Th2 responses can enhance both infectious and allergic disease. Hence, in some cases, a common mechanism may be responsible for effects that are generally considered to be very different. Because cytokines produced in the inflammatory process play a role in modulation of Th cell responses, there is a mechanism by which agents that appear to have only local effects at the portal of entry may, in fact, affect immune responses systemically. An understanding of conditions which trigger certain cytokine responses may be useful not only in understanding inflammation but also in predicting certain kinds of immunosuppressive and allergic responses. Future studies in this area are likely to provide insights into many areas of immunotoxicology.

Association between enhanced Th2/Th1 cytokine profile and donor T-cell chimerism following total lymphoid irradiation

Total lymphoid irradiated (TLI) mice develop antigen specific tolerance if the initial antigen exposure occurs shortly after the completion of TLI. We injected TLI-treated mice with semiallogeneic donor cells at 2, 7, or 28 days after completing TLI and determined the levels of donor CD4 and CD8 cells 5 to 7 weeks after TLI treatment. The level of chimerism correlated with the timing of the initial alloantigen exposure. Donor CD4 and CD8 cells were noted only in day 2 or 7 injected mice. Because donor cell chimerism suggested increased in vivo survival of donor cells, we used the level of donor cell chimerism as a surrogate marker for tolerance to examine the relationship between the development of tolerance and enhanced Th2/Th1 cytokine responses to donor antigen. Increased levels of donor CD4 and CD8 cells in the TLI-treated mice was associated with increased Th2/Th1 cytokine production and decreased CTL activity to donor antigen in vitro. Higher Th2/Th1 cytokine levels also correlated with lower CTL activity. The results indicate that the increased production of Th2/Th1 may function to enhance survival of donor cells in TLI-treated mice and suggest that tolerance induction after TLI treatment involves immunoredirection.

Mechanisms of tolerance to rat heart allografts using posttransplant TLI. Changes in cytokine expression

Lewis rats were rendered tolerant to ACI heart allografts using a regimen of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte or antilymphocyte globulin (RATG or RALG), and a single donor blood transfusion. All three treatment modalities were required to induce tolerance. The mechanism of the maintenance of tolerance was investigated by comparing the secretion of cytokines in the MLR, and the expression of cytokine mRNA in the allografts of tolerant and nontolerant Lewis rats. Although, the 3H-thymidine incorporation and secretion of IL-2 was frequently comparable in the MLR from tolerant and nontolerant rats, the secretion of IFN-gamma was markedly reduced in the tolerant rats. This was reflected in a markedly reduced frequency of cells expressing IFN-gamma mRNA in the allografts of tolerant as compared with nontolerant hosts. The frequency of cells expressing IL-2 and IL-10 mRNA was also reduced, but no significant difference was observed for cells with IL-4 mRNA. Spleen cells from nontolerant rats rapidly rejected ACI allografts in irradiated adoptive hosts, but spleen cells from tolerant rats did not. Evaluation of the cytokine mRNA expression at early and late time points in the allografts of adoptive hosts showed a pattern similar to that of the primary hosts. Thus, the tolerant state was associated with a maintenance or elevation of IL-4 expression and a marked reduction of IFN-gamma expression. Previous reports have shown that TLI alone induced this shift in the early recovery phase after irradiation.

Transfusion of polarized TH2-like cell populations into SCID mouse cardiac allograft recipients results in acute allograft rejection

It has been hypothesized that TH1 cells mediate the archetypical cell-mediated immune response of acute allograft rejection, whereas TH2 cells promote allograft acceptance. To test this, we transfused SCID cardiac allograft recipients with polarized TH1-like or TH2-like graft-reactive T cells, and monitored graft function and graft-reactive immune responses in the graft recipients. Polarized THl-like cells, which were generated in vitro by stimulating syngeneic splenocytes with donor alloantigens in the presence of anti-IL-4 mAb, produced IFNg but not IL-4 when restimulated with donor alloantigen. Polarized TH2-like populations, which are generated in vitro by stimulating syngeneic splenocytes with donor alloantigens in the presence of IL-4, produced IL-4 but not IFNg when restimulated with donor alloantigen. Interestingly, bioassays of culture SN from restimulated TH1 but not TH2 cells revealed IL-2 production, although LDA analyses revealed that the TH1 and TH2 cells had identical frequencies of IL-2-producing cells. Transfusion of THl-like cells into SCID cardiac allograft recipients resulted in acute rejection within 7-10 days that was characterized by cellular infiltration, myocyte necrosis, and edema. Graft-infiltrating cells (GIC) recovered from TH1-transfused animals contained large numbers of graft-reactive IL-2-producing cells (68-269/10(6) GIC), but no LDA-detectable IL-4-producing cells. These data support the hypothesis that donor-reactive TH1 cells can promote acute allograft rejection. In contrast to the hypothesis, transfusion of the polarized TH2-like population into SCID cardiac allograft recipients also resulted in histologically similar acute rejection within 7-10 days. Infiltrating cells recovered from TH1-transfused allografts contained large numbers of graft-reactive (109-1458/10(6) GIC), LDA-detectable, IL-4-producing cells--indicating that the TH2 cells had arrived at the graft-but promoted acute allograft rejection rather than allograft acceptance.

Tissue-specific effects of anti-CD4 therapy in induction of allograft unresponsiveness in high and low responder rats

In these experiments, we studied the role of anti-CD4 (Ox38) monoclonal antibody in the prevention of heart and/or kidney allograft rejection in low (ACI) and high (Lewis) responder rats. In low responder ACI rats, donor-specific tolerance for heart and kidney allografts (individually or in combination) was achieved by pretransplant anti-CD4 therapy. In high responder Lewis rats, anti-CD4 therapy alone (or combined with anti-CD8 (Ox8), thymectomy or total lymphoid irradiation) did not prevent first-set rejection of heart allografts. This difference was correlated with a more profound and longer lasting CD4+ cell depletion in the low responder strain. Anti-CD4 treatment, however, produced tolerance of kidney transplants in high responder rats. Additionally, anti-CD4 treatment induced tolerance to heart (as well as kidney) allografts in Lewis recipients of combined kidney and heart allografts from ACI. The effects of anti-CD4 treatment thus depend upon the recipient responder status as well as the organs transplanted and the order of transplantation.

Functional and phenotypic analysis of in vitro stimulated canine peripheral blood mononuclear cells

The inter-species cross-reactivity of cytokine bioassays for interleukin-2 (IL2) and interleukin-6 (IL6) was investigated in the canine species. The kinetics of normal canine peripheral blood mononuclear cells (PBMC) stimulated with pokeweed mitogen (PWM), were analyzed in terms of cytokine release and responsiveness to cytokine stimulation, in conjunction with determination of cell proliferation, de novo antibody synthesis and cell surface phenotype. PBMC were stimulated with PWM at the beginning of the culture and human recombinant IL2 (rIL2) was added 3-4 days post stimulation (d.p.s.). Mitogenically stimulated cells proliferated and synthesized antibody in a linear fashion up to 6 d.p.s. Resting PBMC had a mean CD4+/CD8+ ratio of 1.7:1; whereas cells stimulated with PWM were predominantly of CD8 phenotype at 7 d.p.s.. Three days after addition of IL2, stimulated cells were predominantly of the Thy+, sIg-, CD4+, CD8- phenotype, with an increase in the CD4+/CD8+ ratio. The magnitude of de novo antibody synthesis was lower in rIL2-supplemented cultures than in cultures stimulated only with PWM, and suggested a negative relationship between de novo antibody synthesis and proliferative responses of the same cultures. Supernatants from mitogen-stimulated cultures induced proliferation of mouse IL2- and IL6-dependent cell lines. Antibodies reactive with human IL2 or IL6 inhibited these responses. IL2-like activity in PWM-stimulated culture peaked by 2 d.p.s. and decreased thereafter. IL6-like activity peaked later (4-6 d.p.s.).

IL-4-based helper activity of CD4+ T cells is radiation sensitive

The capacity of CD4+ T cells to induce IgG synthesis in B cells has been known to be radioresistant for more than 20 years. However, the radiation sensitivity of helper T cells with regard to their ability to induce the synthesis of isotypes other than IgG has not been studied. We therefore irradiated KLH-primed lymph node T cells and examined their capacity to induce IgG, IgM, and IgE synthesis in hapten-primed B cells. We demonstrated that while the capacity of KLH-primed lymph node cells to induce IgG synthesis was not affected by irradiation, the capacity of such T cells to induce IgE synthesis was greatly reduced by gamma-irradiation. This was consistent with our observations that IL-4 and IL-5 synthesis in such cells was greatly diminished by irradiation, whereas IL-2 synthesis was only minimally affected. A similar differential sensitivity to irradiation of the helper activity of Th1 and Th2 clones was observed with regard to their ability to induce IgE and IgG synthesis under cognate conditions. Irradiation greatly inhibited the capacity of Th2 clones to induce IgE synthesis, but only minimally affected the capacity of Th1 clones to induce IgG synthesis in primed B cells. The capacity of irradiated Th2 clones to induce IgE synthesis was restored by the addition of IL-4 and IL-5. These results taken together indicated that the sensitivity to irradiation of T helper cells with regard to the induction of IgE but not IgG synthesis was due to the sensitivity to irradiation of the production of IL-4 but not of IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Disproportionate fetal growth and raised IgE concentration in adult life

A follow-up study was carried out to determine whether either impaired or disproportionate fetal growth are associated with a raised total serum IgE concentration in men and women aged 50 years. The serum IgE concentration was measured in 146 men and 134 women born in Preston (Lancashire, UK) between 1935 and 1943, whose size at birth had been measured in detail. Sixty-two subjects were found to have an IgE concentration above 80 IU/ml. Compared with subjects with a normal IgE on average they had a 0.30 inch larger head circumference at birth (P = 0.004) and weighted 5.6 ounces more at birth (P = 0.04). People with a raised and with a normal IgE were of similar crown-heel length at birth, indicating that in utero those with a raised IgE had had disproportionate growth of the head in relation to the trunk and limbs. The prevalence of a raised IgE rose from 14% in subjects whose head circumference at birth was 13 inches or less to 37% in those whose head circumference was more than 14 inches. This association was independent of gestational age at birth and of the mother's pelvic size and parity. It was also independent of adult physique, social class and smoking, and was similar in men and women. In multiple logistic regression analyses odds ratios of a raised IgE rose progressively to more than 4 as head circumference at birth increased from 13 inches or less to more than 14 inches.(ABSTRACT TRUNCATED AT 250 WORDS)

Particulate Aspergillus fumigatus antigens elicit a TH2 response in BALB/c mice

BACKGROUND

In order to understand the immunoregulation in allergic aspergillosis, a murine model was developed by exposing animals to particulate and soluble antigens of Aspergillus fumigatus.

METHODS

BALB/c mice were exposed to soluble Aspergillus antigen intranasally. Animals showing moderate levels of IgE were subsequently exposed to soluble antigen or antigen conjugated to polystyrene beads intranasally. The IgE and IgG1 in the sera and the eosinophils in the blood and lungs were studied. The spleen and lung mononuclear cells were stimulated with both concanavalin A and antigen and evaluated for production of interleukin (IL)-4, IL-5, IL-10, and interferon-gamma.

RESULTS

Animals exposed to particulate antigens showed more elevated serum IgE levels and increased numbers of eosinophils in the blood and lungs than those exposed to soluble antigen. Lung cell cultures from animals exposed to particulate antigens when stimulated with Aspergillus produced IL-4 and IL-5, indicating a TH2 type of response. Animals exposed to soluble antigens showed a weaker TH2 response, as evidence by low IgE levels in sera, fewer eosinophils in the blood, and low levels of cytokine production from lung and spleen cells.

CONCLUSION

The results indicate that the physical nature of the antigen may have a major role in determining the type of immune response of the host.

The biology of interleukin-5 and its receptor

IL-5 is primarily a T-cell-derived cytokine that has multiple regulatory functions on eosinophils and (in the mouse) on antibody-secreting B cells. A complex network of cytokines appear to control transcription of the gene for IL-5 and its production. Abnormally high levels of this cytokine are associated with infections with tissue-dwelling parasites and a diverse group of hypereosinophilic conditions of no known etiology. Our understanding of the biological role of IL-5 in the regulation of Ig production and the development of immunity to parasites is far from complete, but basic knowledge of its action at the cellular level is accumulating and will be critical for the intelligent application of immunotherapy with IL-5 or antibodies to IL-5 in infectious, neoplastic, and possibly other diseases.

The cellular and molecular basis for divergent allergic responses to chemicals

Chemicals vary with respect to the nature of allergic reactions which they will elicit preferentially. A wide variety of environmental and industrial chemicals are known to cause allergic contact dermatitis (contact sensitivity). Some of these are able also to induce respiratory allergy. This article reviews the characteristics of immune responses to different classes of chemical allergens and the role which functional subpopulations of T helper (TH) cells and their soluble cytokine products play in the induction of allergic sensitization. In addition, new opportunities to identify and classify chemical allergens based upon characterization of divergent allergic responses is discussed.

Antigen concentration determines helper T cell subset participation in IgE antibody responses

A recently developed in vitro system for antigen-stimulated primary and secondary murine IgE antibody responses has been used to define (a) the relative participation of the Th1 and Th2 cell-derived lymphokines IFN-gamma and IL-4, respectively, in such responses, and (b) the role of antigen concentration in determining functional helper T cell activity. These studies confirm that IL-4 and IFN-gamma exert regulatory effects on IgE synthesis, but the nature and extent of their respective effects on primary and secondary IgE responses differ. Thus, primary IgE responses are considerably more sensitive to and dependent on IL-4 than are secondary IgE responses since (1) anti-IL-4 monoclonal antibody totally inhibited primary IgE responses, but only partially affected secondary responses; and (2) exogenously added IL-4 could stimulate primary IgE responses to optimal antigen concentrations, but had no effect on secondary IgE production. Likewise, antigen-stimulated primary IgE responses are about eightfold more sensitive than are secondary responses to the inhibitory effects of IFN-gamma. Studying the effect of antigen dose on the quantity of IgE antibody produced revealed that although IFN-gamma could be detected by ELISA in cultures exhibiting high-dose antigen-dependent diminution of IgE production, anti-IFN-gamma monoclonal antibody could not reverse this phenomenon. Thus, IFN-gamma is not solely responsible for decreased IgE synthesis associated with high-dose antigen exposure. IL-4 activity was detected in the fluid from cultures stimulated with low, but not high, levels of antigen. Moreover, addition of exogenous IL-4 restored IgE production to normal levels in cultures exposed to high antigen concentrations. Therefore, it appears that high levels of antigen result in selective stimulation of Th1 cells which produce IFN-gamma, and diminished activation of IL-4-producing Th2 cells. These results help explain observations regarding the influence of antigen dose on the generation of experimental and clinical IgE antibody responses in vivo.

IgG subclass responses to Theiler's murine encephalomyelitis virus infection and immunization suggest a dominant role for Th1 cells in susceptible mouse strains

Inbred mouse strains differ in susceptibility to Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease. A strong correlation between disease susceptibility and delayed-type hypersensitivity (DTH) has been previously demonstrated, but no strong correlation between disease susceptibility and total anti-TMEV ELISA titres was shown. Since both DTH and IgG2a antibody production are regulated by CD4+ Th1 cells, we investigated three strains of mice to determine whether antivirus IgG2a antibody levels, like DTH in previous studies, correlated with disease susceptibility. Susceptible SJL/J, intermediately susceptible C3H/HeJ, and resistant C57BL/6 mice were infected intracerebrally (i.c.) with the BeAn strain of TMEV and monitored for clinical signs of demyelination and for levels of TMEV-specific antibody of different IgG subclasses using a particle concentration fluorescence immunoassay (PCFIA). Resistant C57BL/6 mice were found to have significantly lower concentrations of total anti-TMEV antibody than susceptible SJL/J mice and intermediately susceptible C3H/HeJ mice show variable antibody responses. A predominance of anti-TMEV IgG2a (Th1 regulated) antibody was seen in susceptible and intermediately susceptible mice, whereas resistant mice displayed a predominant anti-TMEV IgG1 (Th2 regulated) response accompanied by a marked deficiency of IgG2a. In contrast, immunization of C57BL/6 mice with UV-inactivated TMEV in adjuvant revealed that this strain was not defective either in its ability to generate high levels of anti-TMEV antibody or in its ability to produce IgG2a antibody. These results suggest that the antivirus IgG subclass profile is dependent upon the immunization route, virus viability and/or the use of adjuvant and that the levels of antivirus subclasses may be predictive of disease susceptibility.

Divergent immune responses to respiratory and contact chemical allergens: antibody elicited by phthalic anhydride and oxazolone

In previous studies we observed that exposure of mice to the contact allergen 2,4-dinitrochlorobenzene (DNCB) and the respiratory allergen trimellitic anhydride (TMA) resulted in qualitatively different immune responses characteristic of selective Th1- and Th2-type T helper cell activation respectively. The purpose of the present investigation was to determine whether the effects recorded with DNCB and TMA are characteristic of immune responses to contact and respiratory chemical allergens in general. Experiments have been performed with phthalic anhydride, a known human respiratory sensitizer, and with oxazolone, a potent contact allergen. Under conditions of exposure where both chemicals elicited an IgG anti-hapten antibody response, only phthalic anhydride caused an increase in the serum concentration of IgE. Furthermore, like TMA, phthalic anhydride preferentially induced IgG2b rather than IgG2a antibody. In contrast, oxazolone, like DNCB, induced a markedly stronger IgG2a than IgG2b antibody response. These data provide confirmatory evidence that chemical respiratory allergens and chemical contact allergens elicit qualitatively different immune responses which reflect their clinical effects in man.

Thymic irradiation inhibits the rapid recovery of TH1 but not TH2-like functions of CD4+ T cells after total lymphoid irradiation

Four to six weeks after total lymphoid irradiation (TLI), there is a selective deficit in the CD4+ T cells which secrete IL-2, proliferate in the MLR, and induce GVHD (Th1-like functions). A similar deficit in CD4+ T cells which secrete IL-4 and help antibody responses (Th2-like functions) is not observed. In the present study, shielding of the thymus with lead during TLI increased the Th1-like functions of CD4+ cells. Mice without thymus shields showed a marked selective reduction in the medullary stromal cells identified with the monoclonal antibody, MD1, and the severe reduction was prevented with thymus shields. Thus, shielding the thymus prevents the depletion of thymic medullary stromal cells and allows for a rapid recovery of Th1-like functions in the mouse spleen after TLI. Th2-like functions recover rapidly after TLI whether or not the thymus is irradiated.

Selective activation of Th1- and Th2-like cells in vivo--response to human collagen IV

Mice immunized with human collagen IV develop either antibody responses or T-cell proliferative responses as a function of the MHC genotype of the immunized mice. CD4+ T cells, similar to Th1 and Th2 cells, participate in these two types of responses, with CD4+ T-cell proliferative responses associating with IL-2 and IFN gamma release, and antibody production associating with CD4+ T-cell IL-4 and IL-5 release. Thus it would appear that the same antigen can induce responses consistent with either cell-mediated or humoral immunity depending on MHC class II genotype. In attempting to understand how MHC genotype controls the class of immunity observed several models are discussed. It was proposed, based on results obtained upon priming with human collagen IV, that the activation of Th1 and Th2 responses may be regulated at several levels (presentation by different APCs, presentation of different densities of the T-cell receptor ligand and presentation of different T-cell epitopes). With the identification of the peptide recognized by the CD4+ T cells, it was clear that the inability to induce Th1 responses in H-2b and the inability to induce Th2 responses in H-2s could not be accounted for by the failure to generate an immunodominant peptide during processing or the failure of the peptides to bind to the MHC class II molecules. Furthermore, the difference in the type of response generated could not be explained by the use of different peptides of the human collagen IV molecule in the two mouse strains, as a single peptide will induce both types of CD4+ T-cell response. However, it cannot be ruled out that the a2 peptide-class II interaction forms different T-cell ligands in the two strains either because the two class II MHC molecules are different or that the peptide is processed and reveals a different antigenic activity (Fox et al. 1988). Perhaps the most important finding from the peptide studies is that the lack of proliferative response in H-2b mice is not absolute, but can be overcome either by priming with high doses of the a2 peptide or by increasing the amount of peptide needed to elicit a recall response. It seems reasonable to speculate that changes in the dose required for priming Th1 or Th2 responses may reflect differences in the activation requirements of the two types of cells with Th1 cells requiring a high ligand density and Th2 cells a low ligand density.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-lived reciprocal regulation of antigen-specific IgE and IgG2a responses in mice treated with glutaraldehyde-polymerized ovalbumin

Previously, we discovered that administration of high Mr glutaraldehyde-polymerized ovalbumin (OA) to C57BL/6 mice prior to immunization with OA in A1(OH)3 adjuvant resulted in induction of an interferon-gamma (IFN-gamma) dependent, split tolerance in which maximal OA-specific IgE responses were 1-3% of those observed in saline-treated OA-[A1(OH)3] immunized controls. Concomitantly, these mice exhibited up to 10(3)-fold increases in OA-specific IgG2a synthesis. In this report we examine the longevity and resilience of these reciprocal effects on IgE inhibition/IgG2a enhancement over extended periods of time and following multiple re-exposures to the sensitizing allergen. The data indicate that the T-cell mediated changes in responsiveness which are induced upon exposure to glutaraldehyde-modified protein allergen, but not unmodified allergen, are (i) extremely long-lived (greater than 350 days); (ii) resistant to at least five re-immunizations with OA in A1(OH)3 adjuvant; and (iii) antigen-specific. The results are consistent with a virtually permanent shift in the OA-specific T-cell repertoire in vivo from one dominated by Th2-like patterns of cytokine synthesis (IL-4) to one dominated by Th1-like (IFN-gamma) cytokine production.

Thymic modulation of IL-2 and IL-4 synthesis by peripheral T cells

In this paper we provide several lines of evidence to support the hypothesis that the thymus can exert regulatory influences on the functional capabilities of mature recirculating T cells. Our studies demonstrate that while the IL-2-producing potential of T cells that repopulate the secondary lymphoid organs of lethally irradiated and stem cell-reconstituted mice is significantly reduced compared to that of T cells harvested from normal mice, the amount of IL-4 produced by the T cells of these experimental animals is equivalent to, or greater than, the amount produced by T cells from control animals. In addition, we determined that the amount of biologically active IL-2 and IL-4 secreted by T cells harvested from lethally irradiated animals who reconstitute their hematopoietic and immune systems under the influence of nonirradiated thymic epithelial grafts is essentially identical to the amount produced by T cells harvested from nonirradiated control animals. Collectively, these findings suggest that: (1) the alterations observed in the lymphokine-producing potential of T cells harvested from lethally irradiated and stem cell-reconstituted mice is not due to a direct effect of ionizing radiation on the T lymphocytes themselves, and (2) the exposure of the epithelial cells of the thymus to ionizing radiation during marrow-ablative regimens abrogates or modifies a component of thymic function which can influence the lymphokine-secreting potential of recirculating T cells. Further evidence for thymic involvement in the regulation of lymphokine production by peripheral T cells comes from our finding of a post-thymectomy time-dependent reduction in the capacity of T cells from animals to produce IL-2. Coincident with this reduction, T cells harvested from peripheral lymphoid organs of thymectomized animals demonstrated an augmentation in their IL-4-producing capabilities. The finding that treatment of thymectomized animals with the androgen steroid hormone dehydroepiandrosterone reestablished a normal IL-2-producing potential by their T cells makes it unlikely that the reduced capacity to produce IL-2 was secondary to a loss in fresh thymic emigrants.