Raising root zone temperature improves plant productivity and metabolites in hydroponic lettuce production

While it is commonly understood that air temperature can greatly affect the process of photosynthesis and the growth of higher plants, the impact of root zone temperature (RZT) on plant growth, metabolism, essential elements, as well as key metabolites like chlorophyll and carotenoids, remains an area that necessitates extensive research. Therefore, this study aimed to investigate the impact of raising the RZT on the growth, metabolites, elements, and proteins of red leaf lettuce. Lettuce was hydroponically grown in a plant factory with artificial light at four different air temperatures (17, 22, 27, and 30°C) and two treatments with different RZTs. The RZT was raised 3°C above the air temperature in one group, while it was not in the other group. Increasing the RZT 3°C above the air temperature improved plant growth and metabolites, including carotenoids, ascorbic acids, and chlorophyll, in all four air temperature treatments. Moreover, raising the RZT increased Mg, K, Fe, Cu, Se, Rb, amino acids, and total soluble proteins in the leaf tissue at all four air temperatures. These results showed that raising the RZT by 3°C improved plant productivity and the metabolites of the hydroponic lettuce by enhancing nutrient uptake and activating the metabolism in the roots at all four air temperatures. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology. Overall, this research demonstrates that plant growth and metabolites can be improved simultaneously with an increased RZT relative to air temperature. This study serves as a foundation for future research on optimizing RZT in relation to air temperature. Further recommended studies include investigating the differential effects of multiple RZT variations relative to air temperature for increased optimization, examining the effects of RZT during nighttime versus daytime, and exploring the impact of stem heating. This research has the potential to make a valuable contribution to the ongoing growth and progress of the plant factory industry and fundamental advancements in root zone physiology.

Controlling root zone temperature improves plant growth and pigments in hydroponic lettuce

BACKGROUND AND AIMS

Air and root zone temperatures are important environmental factors affecting plant growth and yield. Numerous studies have demonstrated that air temperature strongly affects plant growth and development. Despite the extensive literature on air temperature, comprehensive studies on the effects of root zone temperature (RZT) on plant growth, elemental composition, and pigments are limited. In this study, we carefully observed the effects of RZT in red leaf lettuce to understand its effect on lettuce growth and pigment content.

METHODS

Lettuce (Lactuca sativa, red leaf cultivar 'Red Fire') was grown hydroponically in a plant factory with artificial light under three RZT treatments (15, 25, or 35 °C) for 13 days. We investigated the comprehensive effects of RZT on the production of red leaf lettuce by metabolome and ionome analyses.

KEY RESULTS

The 25 °C RZT treatment achieved maximum shoot and root dry weight. The 35 °C RZT decreased plant growth but significantly increased pigment contents (e.g. anthocyanins, carotenoids). In addition, a RZT heating treatment during plant cultivation that changed from 25 to 35 °C RZT for 8 days before harvest significantly increased shoot dry weight compared with the 35 °C RZT and significantly increased pigments compared with the 25 °C RZT. The 15 °C RZT resulted in significantly less pigment content relative to the 35 °C RZT. The 15 °C RZT also resulted in shoot and root dry weights greater than the 35 °C RZT but less than the 25 °C RZT.

CONCLUSIONS

This study demonstrated that plant growth and pigments can be enhanced by adjusting RZT during different stages of plant growth to attain enhanced pigment contents while minimizing yield loss. This suggests that controlling RZT could be a viable method to improve lettuce quality via enhancement of pigment content quality while maintaining acceptable yields.

Polymorphisms in the tumor necrosis factor (TNF) genes are associated with susceptibility to effects of ultraviolet-B radiation on induction of contact hypersensitivity

We investigated the allelic distributions of single nucleotide polymorphisms (SNPs) of the TNFA, TNFB and IKBL genes, 3 microsatellites within the tumor necrosis factor (TNF) region of HLA locus, and the HLA phenotypes as well as the TLR4 gene in Chromosome 9 in 26 healthy Caucasian volunteers. These individuals were also assessed as ultraviolet B (UVB)-susceptible (S) or UVB-resistant (R). Our results identified 12 UVB-S and 14 UVB-R individuals. Attempts to correlate particular HLA-A, -B, -C, and -DR antigens with the UVB phenotypes failed. Similarly, attempts to correlate SNP at the NcoI-RFLP within intron 1 of the TNFB, IKBL and TLR4 gene with UVB phenotypes also failed. However, microsatellite analyses of TNFa, TNFc, and TNFd markers revealed a significant increase in the frequencies of TNFa2 in UVB-S individuals (P=0.00032) and of TNFd3 in UVB-R individuals (P=0.012). Moreover, DNA sequencing analyses of 5 SNPs of the TNFA promoter region revealed a significant increase in the frequency of the allele B of the TNFA gene (TNFApB) representing the nucleotide A at position -863 and C at position -1031 (P=0.015). Since it is known that TNFa2 and TNFApB is a high TNF-alpha responder, whereas TNFd3 is a TNF-alpha low responder, we propose that the TNF region of HLA contains polymorphic genes that confer susceptibility and resistance to the deleterious effects of UVB radiation on the induction of contact hypersensitivity. This proposal is consistent with previous reports that a unique microsatellite region of the Tnfa gene in mice contains alleles that dictate the UVB-dependent phenotypes in mice, and implicate TNF-alpha as the primary mediator of the immune-damaging effects of UVB radiation.

Hapten-specific tolerance induced by acute, low-dose ultraviolet B radiation of skin requires mast cell degranulation

The deleterious effects of ultraviolet B radiation (UVR) on cutaneous immunity are mediated in part by cytokines released from cutaneous cells following radiation exposure. On the one hand, TNF-alpha has been advocated as the primary mediator of failed contact hypersensitivity induction, and, on the other hand, IL-10 has been held responsible for tolerance. While keratinocytes exposed to UVR have been found to produce both TNF-alpha and IL-10, there is reason to question whether these major cellular constituents of the epidermis are the relevant source of immunomodulatory cytokines after UVR. Dermal mast cells also produce TNF-alpha and IL-10, and we have recently reported that mast cell-derived TNF-alpha is required for UVR-induced impairment of CH induction. In this study, we have examined whether mast cells are also a relevant source of IL-10 in UVR-dependent tolerance. We found that (a) UVR fails to induce tolerance in mast cell-deficient mice, and (b) that tolerance occurs if mast cells are triggered to degranulate after ligation of the IgE receptor. Both types of tolerance were neutralized with anti-IL-10 antibodies, are hapten specific, and are associated with regulatory lymphoid cells. We conclude that mast cells are required in UVR-induced tolerance and may be one of the major sources of IL-10 that mediates the tolerance induced by acute, low-dose UVR.

Hapten-specific tolerance induced by acute, low-dose ultraviolet B radiation of skin requires mast cell degranulation

The deleterious effects of ultraviolet B radiation (UVR) on cutaneous immunity are mediated in part by cytokines released from cutaneous cells following radiation exposure. On the one hand, TNF-alpha has been advocated as the primary mediator of failed contact hypersensitivity induction, and, on the other hand, IL-10 has been held responsible for tolerance. While keratinocytes exposed to UVR have been found to produce both TNF-alpha and IL-10, there is reason to question whether these major cellular constituents of the epidermis are the relevant source of immunomodulatory cytokines after UVR. Dermal mast cells also produce TNF-alpha and IL-10, and we have recently reported that mast cell-derived TNF-alpha is required for UVR-induced impairment of CH induction. In this study, we have examined whether mast cells are also a relevant source of IL-10 in UVR-dependent tolerance. We found that (a) UVR fails to induce tolerance in mast cell-deficient mice, and (b) that tolerance occurs if mast cells are triggered to degranulate after ligation of the IgE receptor. Both types of tolerance were neutralized with anti-IL-10 antibodies, are hapten specific, and are associated with regulatory lymphoid cells. We conclude that mast cells are required in UVR-induced tolerance and may be one of the major sources of IL-10 that mediates the tolerance induced by acute, low-dose UVR.

Suprathreshold doses of hapten are required to induce both contact hypersensitivity and tolerance

Whereas both high (conventional) and low (optimal) doses of epicutaneously applied hapten induce contact hypersensitivity in normal mice, only conventional doses retain their capacity to induce contact hypersensitivity after acute, low dose ultraviolet B radiation in UVB-resistant mice. Recent evidence indicates that conventional doses of hapten as well as acute, low dose ultraviolet B radiation destroy virtually all epidermal Langerhans cells, which leads to the conclusions that (a) dermal antigen presenting cells have a prominent role to play in contact hypersensitivity induction, and that (b) Langerhans cell provide this function only in normal skin, and only if non-toxic amounts of hapten are present. We have now explored the ability of suprathreshold, threshold, and sub-threshold doses of hapten to induce tolerance when painted on or injected into normal skin or skin exposed to ultraviolet B radiation. Our results indicate that a single exposure of low dose, ultraviolet B radiation generated tolerance-promoting signals within the epidermis when a threshold dose of hapten was painted on the exposed site. By contrast, suprathreshold doses of hapten painted on skin after four consecutive daily doses of ultraviolet B radiation led to tolerance that arose exclusively from cells within the dermis. In absence of ultraviolet B radiation, epicutaneously applied hapten failed uniformly to induce tolerance, whether applied at suprathreshold, threshold or sub-threshold doses. We conclude that normal skin lacks cells with inherent tolerance-promoting capacity, but that cells of this type can emerge within either epidermis or dermis after exposure to acute, low dose ultraviolet B radiation.

Maintaining remission of lupus erythematosus profundus (LEP) with cyclosporin A

We report a young female patient with recurrent lupus erythematosus profundus (LEP) who has successfully maintained remission of LEP with cyclosporin A (CsA), although conventional treatments such as systemic corticosteroids (low-dose), dapsone, and other immunosuppressive drugs (azathiopurine, cyclophosphamide) could not maintain remission.

Genetic factors in immunosuppression: precise genetic evidence that polymorphism of TNF-alpha dictates UVB-susceptibility in mice

Acute low-dose treatment of murine skin with ultraviolet B (UVB) light impairs induction of contact hypersensitivity (CH) to dinitrofluorobenzene (DNFB) in certain inbred strains of mice (termed UVB-susceptible), but not in others (termed UVB-resistant). These deleterious effects of ultraviolet radiation (UVR) are mediated in part by TNF-alpha, which is released from UVR-exposed epidermal and dermal cells. To test the hypothesis that polymorphism of TNF-alpha governs the phenotype of UVB-susceptibility in vivo, various strains of mice received UVB radiation followed by hapten application to induce contact hypersensitivity. Results suggest that the polymorphism at the Tnf-alpha locus dictates UVB susceptibility in vivo.

Studies of delayed systemic effects of ultraviolet B radiation (UVR) on the induction of contact hypersensitivity, 2. Evidence that interleukin-10 from UVR-treated epidermis is the critical mediator

Acute, low-dose ultraviolet B radiation (UVR) alters cutaneous immunity at the local site as well as systemically. Within 2-3 days of UVR exposure, recipient mice lose their capacity to develop contact hypersensitivity (CH) when hapten is painted on unexposed skin. This loss correlates temporally with a functional deficit among dendritic antigen-presenting cells within non-draining lymph nodes and spleen. In the experiments described, the delayed systemic immune deficiency following acute, low-dose UVR exposure was found to be eliminated with neutralizing anti-interleukin-10 (IL-10) antibody. Intracutaneous injection of IL-10 generated a deficiency of systemic immunity as well as a functional deficit among lymph node dendritic cells that was similar to that induced by UVR. The skin itself was found to be the source of the IL-10 responsible for these defects, and epidermis (presumably keratinocytes) rather than mast cells was found to be the source of IL-10 within UVR-exposed skin. The potential relationships are discussed between the delayed systemic immune deficit created by acute, low-dose UVR, and the systemic immune deficits caused by chronic, high-dose UVR and by a single, high-dose UVR exposure.

Tumor necrosis factor-alpha impairs contact hypersensitivity induction after ultraviolet B radiation via TNF-receptor 2 (p75)

Acute, low dose ultraviolet B radiation (UVR) impairs induction of contact hypersensitivity (CH) in genetically susceptible mice. Polymorphic alleles at the TNF-alpha locus dictate the susceptibility phenotype, and neutralizing anti-TNF-alpha antibodies restore CH induction in mice exposed to UVR. This circumstantial evidence strongly implicates TNF-alpha in the pathogenesis of failed CH induction after UVR. Using mice genetically deficient in TNF-receptor 1 (p55) or TNF-receptor 2 (p75), we now report that the capacity of TNF-alpha to impair CH induction after UVR required signaling via TNF-receptor 2, rather than TNF-receptor 1. Moreover, acting via the same receptor, TNF-alpha altered the density and morphology of class II MHC-bearing epidermal Langerhans cells. However, UVR retained its capacity to induce tolerance in both TNF-receptor 1 and TNF-receptor 2 deficient mice, indicating that TNF-alpha plays no role in the systemic immune deficit created by UVR.

Role of CD4+ T cells in immunobiology of orthotopic corneal transplants in mice

PURPOSE

To determine, with the use of mice genetically deficient in expression of CD4 or CD8 molecules, which T cells are responsible for rejection of orthotopic corneal allografts in mice.

METHODS

Corneas were prepared from major histocompatibility complex (MHC)-only incompatible, minor histocompatibility (H)- only incompatible, and MHC-plus-minor H incompatible donors and grafted orthotopically to eyes of CD4 knockout (KO), CD8KO, and wild-type control mice. Graft survival patterns were assessed clinically and compared. Mice that retained healthy corneal allografts beyond 8 weeks were evaluated for evidence of donor-specific tolerance and anterior-chamber-associated immune deviation (ACAID) using local adoptive transfer reactions and challenge with orthotopic skin allografts.

RESULTS

Corneas grafted to CD8KO mice were rejected with an incidence and tempo indistinguishable from that in wild-type control animals. By contrast, MHC-only, and minor-H-only incompatible corneal grafts survived indefinitely in eyes of CD4KO mice. Approximately 50% of corneal grafts that confronted CD4KO recipients with both MHC and minor H alloantigens experienced delayed rejection, whereas similar grafts in wild-type recipients were rejected acutely. CD4KO mice with long-accepted grafts displayed neither donor-specific ACAID nor allograft tolerance.

CONCLUSIONS

CD8+ T cells play little or no role in acute rejection of orthotopic corneal allografts. Instead, acute rejection is mediated almost exclusively by CD4+ T cells. Moreover, when corneal allografts survive for 8 weeks without acute rejection, CD4+ T cells promote donor-specific ACAID thereby insuring long-term graft acceptance.

Genetic mapping and physical cloning of UVB susceptibility region in mice

One of the most important goals of cancer research is to identify environmental and host factors that contribute to the malignant state. Human skin cancers are among the few tumor types for which the predominant environmental carcinogen is known. Ultraviolet light, a component of sunlight, is an important cause of skin cancer in humans. In humans and mice, ultraviolet B radiation induces systematic and local immunosuppression. A consequence of that is inappropriate immune surveillance of somatic tissues for evidence of malignantly transformed cells. The impairment of contact hypersensitivity, as it develops early and correlates well with tumor frequency in various mouse strains, has been used for over 15 y as a model of immunologic events occurring in photocarcinogenesis. In mice, as well as in humans, ultraviolet B radiation induced impairment of contact hypersensitivity is not uniform in all individuals; some individuals are susceptible to the deleterious effects of ultraviolet B, whereas others are resistant to ultraviolet B. We have defined the genetic locus responsible for ultraviolet B susceptibility and resistance in mice within the Bat5 and H-2D segment of the mouse chromosome 17.

A substance p agonist acts as an adjuvant to promote hapten-specific skin immunity

Because substance p (SP) has been reported to be released from cutaneous sensory nerve endings after hapten application, we determined whether SP participates in contact hypersensitivity (CH) induction by using a SP agonist, GR73632 or delta-Aminovaleryl [Pro9, N-Me-Leu10]-substance P(7-11) and a SP antagonist, spantide I. When injected intradermally, SP agonist enhanced CH induced by conventional, but not optimal, sensitizing doses of hapten. By contrast, SP antagonist inhibited the induction of CH by optimal sensitizing doses of hapten. Moreover, SP agonist promoted CH induction and prevented tolerance when hapten was painted on skin exposed to acute, low-dose ultraviolet-B radiation. Intradermally injected SP agonist altered neither the density nor the morphology of epidermal Langerhans cells, implying that SP agonist enhanced the generation of hapten-specific immunogenic signals from the dermis. It is proposed that SP is a natural "adjuvant" that promotes the induction of CH within normal skin. Although exogenous SP agonist can prevent impaired CH and tolerance after ultraviolet-B radiation, the susceptibility of native SP to local neuropeptidases renders the neuropeptide unable to prevent the deleterious effects of ultraviolet-B radiation on cutaneous immunity.

Vitamin C abrogates the deleterious effects of UVB radiation on cutaneous immunity by a mechanism that does not depend on TNF-alpha

Acute low-dose treatment of murine skin with ultra violet B (UVB) light impairs induction of contact hypersensitivity (CH) to dinitrofluorobenzene (DNFB) in certain inbred strains of mice (termed UVB-susceptible), but not in others (termed UVB-resistant), and promotes tolerance. These deleterious effects of ultraviolet radiation (UVR) are mediated in part by TNF-alpha, which is released from UVR-exposed epidermal and dermal cells. Because UVR damage to skin has also been ascribed in part to the generation of reactive oxygen intermediates (ROIs) such as superoxide anion (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH-), and singlet oxygen ((1)O2), we investigated whether vitamin C (ascorbic acid), which can nullify ROIs, prevents the deleterious effects of UVR on the cutaneous immune system. We found that epicutaneous application of vitamin C (10% L-ascorbic acid solution) abrogated the deleterious effects of acute low-dose UVR on induction of CH and prevented the induction of tolerance. Vitamin C, however, did not reverse the effects of TNF-alpha on CH induction and tolerance. These results indicate that (i) ROIs generated intracutaneously by UVR contribute to the impaired ability of exposed skin to support the induction of CH and to promote the induction of tolerance and (ii) these effects are not dependent on TNF-alpha.

Role of F4/80+ cells during induction of hapten-specific contact hypersensitivity

F4/80, a monoclonal antibody that binds to a surface molecule on mature macrophages and certain dendritic cells, has been used to explore the role of epidermal and dermal cells as antigen-presenting cells (APC) during the induction of contact hypersensitivity (CH) in mice. Systemic administration of the antibody appeared to have little or no physical or functional effect on intraepidermal Langerhans' cells, even though a subpopulation of these cells expressed the F4/80 ligand. None the less, systematically administered F4/80 antibodies were able to impair CH induction when dinitrofluorobenzene (DNFB) was painted on normal body wall skin of BALB/c mice [an ultraviolet B (UVB)-resistant strain]. Interestingly, systemic F4/80 antibodies did not affect CH induction in C57BL/10 mice (a UVB-susceptible strain). When a sensitizing dose of hapten was injected intracutaneously (i.c.) into F4/80-treated BALB/c and C57BL/10 mice, CH induction was impaired in both inbred strains, although the severity of impairment was greater in BALB/c mice. Following UVB radiation of body wall skin, anti-F4/80-treated BALB/c mice displayed very feeble CH, whether hapten was painted epicutaneously or injected i.c. at the irradiated site. Based on these and other recent reported results, it is concluded that (1) BALB/c mice rely partially upon dermal, F4/80+ cells as a source of APC when hapten is applied epicutaneously, whereas C57BL/10 mice rely almost exclusively upon epidermal Langerhans' cells in this circumstance; and (2) after UVB radiation of skin, BALB/c mice can use F4/80+ dermal cells as the source of APC function when hapten is painted epicutaneously. These findings are discussed with respect to the cellular basis for the differential susceptibilities of genetically defined strains of mice to the deleterious effects of UVB radiation on CH induction.

Relationship between ultraviolet radiation-induced immunosuppression and carcinogenesis

The capacity of ultraviolet B (UVB) radiation to damage the cutaneous immune system has been extensively documented, and there is good reason to believe that UVB-induced damage is a critical, albeit permissive, factor in the development of sunlight-induced skin cancers. A summary of the evidence shows that acute, low-dose UVB protocols, which resemble quantitatively and qualitatively the manner in which human beings typically experience sun exposure, alter the cutaneous immune system in at least two important ways: they impair the induction of contact hypersensitivity to cutaneous antigens, and induce antigen-specific tolerance. In mice there is compelling evidence that immunogenetic factors dictate whether UVB radiation will impair contact hypersensitivity induction or not. The genetic loci that contain the relevant polymorphic alleles include tumor necrosis factor-alpha and lipopolysaccharide. Because the effects of UVB radiation on contact hypersensitivity induction are mimicked by intracutaneous injections of subinflammatory doses of tumor necrosis factor-alpha or cis-urocanic acid, the favored hypothesis to explain the mechanism of action of UVB radiation in UVB-susceptible individuals is that UVB-dependent transformation of trans- to cis-urocanic acid in the epidermis triggers the intracutaneous release of excess amounts of tumor necrosis factor-alpha. By transiently immobilizing Langerhans cells and other local antigen-presenting cells within the skin, the requirement that hapten be brought to the draining lymph node to sensitive naive hapten-specific T cells is not met, and contact hypersensitivity fails to develop. Because the UVB-susceptibility and UVB-resistance traits have also been demonstrated in human beings, the hypothesis is advanced that these traits are similarly under control of immunogenetic factors, and that a constellation of immune susceptibility genes contributes to the risk of developing sunlight-induced skin cancer. The cellular and molecular basis of UVB-induced tolerance is not as well described, but current evidence suggests that different mechanisms, and presumably different polymorphic genes, dictate whether tolerance will emerge after UVB exposure in mice. Because acute, low-dose UVB also induces tolerance in human beings, the immunogenetic factors that dictate tolerance of this type may also contribute to the risk of developing sunlight-induced skin cancer.

Role of phagocytic macrophages in induction of contact hypersensitivity and tolerance by hapten applied to normal and ultraviolet B-irradiated skin

Liposomes containing the drug dichloromethylene diphosphonate (Cl2MDP) can eliminate phagocytic cells, such as macrophages, when injected in vivo. In this paper we report that Cl2MDP-containing liposomes have been used experimentally to determine the extent to which cutaneous macrophages participate (1) in the induction of contact hypersensitivity (CH) when hapten is painted on normal murine skin, and (2) in the induction of CH or tolerance when hapten is painted on murine skin that has been exposed to ultraviolet B (UVB) radiation. Intradermal (i.d.) injections of Cl2MDP-containing liposomes were found to have no deleterious effects on CH induction via normal skin, whether the amount of hapten (dinitrofluorobenzene) applied to the cutaneous surface was optimal or excessive. Moreover, Cl2MDP-containing liposomes did not deplete the epidermis of Langerhans' cells. However, similar i.d. injections of Cl2MDP-containing liposomes did prevent the induction of CH when hapten was painted on UVB-irradiated skin of BALB/c mice, a strain that develops CH when hapten is applied to UVB-exposed skin. These findings indicate that the antigen-presenting cell (APC) function found in skin of UVB-resistant mice following exposure to UVB radiation can be attributed to macrophages. This explains why these mice develop and display CH after UVB radiation. By contrast, i.d. injections of Cl2MDP-containing liposomes failed to prevent the induction of the tolerance when hapten was applied to the surface of UVB-exposed skin of UVB-susceptible mice, such as C57BL/6. Since the dermis of UVB-exposed skin of these mice is known to contain a novel population of cells that can provide a tolerance-conferring signal, the current findings rule out macrophages as the responsible cell type.

Immune surveillance and sunlight-induced skin cancer

Immune surveillance poses the existence of a recirculating pool of lymphocytes that migrate randomly through somatic tissues. Upon recognition of neoantigens on malignantly transformed cells, lymphocytes proceed to attack and destroy degenerate cells before a tumor emerges. Here, J. Wayne Streilein and colleagues review the effects of ultraviolet B irradiation on the induction of cutaneous immunity in the skin of mice and humans. Furthermore, they discuss the possibility of a genetic predisposition to skin cancer, mediated by a defect in the normal process by which contact hypersensitivity, and therefore immunogenicity, is elicited.

Role of dermal cells from normal and ultraviolet B-damaged skin in induction of contact hypersensitivity and tolerance

With conventional regimens for induction of contact hypersensitivity with highly reactive haptens, circumstantial evidence implicates both epidermal and dermal APC. However, similar applications of hapten to skin that has been treated with an acute, low dose UVB radiation protocol induce contact hypersensitivity only in certain genetically defined strains of mice, termed UVB-resistant. Moreover, mice that fail to acquire contact hypersensitivity when hapten is painted on UVB-exposed skin display hapten-specific tolerance. In the present study, dermal cell suspensions have been prepared from normal and UVB-exposed mouse skin as a means of identifying the cell(s) that: 1) provide APC function after UVB radiation in UVB-resistant mice; and 2) confer tolerance after UVB radiation in UVB-susceptible mice. The results confirm that the normal murine dermis contains Ia+ cells that, when hapten-derivatized in vitro and injected s.c. into naive, syngeneic mice, possess typical Ag-presenting function. Cells with similar function are retained in the dermis of UVB-resistant mice after exposure to UVB radiation, whereas dermal cells of UVB-exposed skin of UVB-susceptible mice display no ability to induce contact hypersensitivity. Instead, the latter dermal cells, when hapten-conjugated and injected s.c., induce tolerance. Thus, doses of UVB radiation that deplete the epidermis of Langerhans cells do not deplete the dermis of UVB-resistant mice of contact hypersensitivity-inducing APC, but do confer upon cells within the dermis of UVB-susceptible mice the capacity to induce unresponsiveness.

Role of dermal cells from normal and ultraviolet B-damaged skin in induction of contact hypersensitivity and tolerance

With conventional regimens for induction of contact hypersensitivity with highly reactive haptens, circumstantial evidence implicates both epidermal and dermal APC. However, similar applications of hapten to skin that has been treated with an acute, low dose UVB radiation protocol induce contact hypersensitivity only in certain genetically defined strains of mice, termed UVB-resistant. Moreover, mice that fail to acquire contact hypersensitivity when hapten is painted on UVB-exposed skin display hapten-specific tolerance. In the present study, dermal cell suspensions have been prepared from normal and UVB-exposed mouse skin as a means of identifying the cell(s) that: 1) provide APC function after UVB radiation in UVB-resistant mice; and 2) confer tolerance after UVB radiation in UVB-susceptible mice. The results confirm that the normal murine dermis contains Ia+ cells that, when hapten-derivatized in vitro and injected s.c. into naive, syngeneic mice, possess typical Ag-presenting function. Cells with similar function are retained in the dermis of UVB-resistant mice after exposure to UVB radiation, whereas dermal cells of UVB-exposed skin of UVB-susceptible mice display no ability to induce contact hypersensitivity. Instead, the latter dermal cells, when hapten-conjugated and injected s.c., induce tolerance. Thus, doses of UVB radiation that deplete the epidermis of Langerhans cells do not deplete the dermis of UVB-resistant mice of contact hypersensitivity-inducing APC, but do confer upon cells within the dermis of UVB-susceptible mice the capacity to induce unresponsiveness.

Characterization of the immunogenetic basis of ultraviolet-B light effects on contact hypersensitivity induction

Ultraviolet-B (UVB) light has proven to be deleterious to the skin immune system in mice, and one major consequence is impairment of the induction of contact hypersensitivity (CH) to haptens applied to UVB-exposed skin. It has been shown recently that the damaging effects of UVB on CH are mediated primarily by tumour necrosis factor-alpha (TNF-alpha). Moreover, not all strains of mice are equally susceptible to the deleterious effects of UVB. Mice that develop CH when hapten is applied to UVB-exposed skin are termed UVB-resistant (UVB-R), whereas mice that fail to acquire CH under these circumstances are termed UVB-susceptible (UVB-S). In the present experiments, we have characterized the UVB-susceptibility of numerous, genetically disparate inbred strains of mice by applying dinitrofluorobenzene (DNFB) epicutaneously to normal and to UVB-exposed body wall skin. The results indicate that the intensities of CH responses of these different strains were distributed in a bimodal fashion, with means at 92% and 28.5% of positive control responses. Among the strains with CH values distributed around the higher mean (i.e. UVB-R mice), the intensity of CH responses after UVB irradiation was uniformly greater than 75% of the intensity found among their positive controls. By contrast, among the strains with CH values distributed around the lower mean (i.e. UVB-S mice), the intensity of CH responses after UVB exposure was uniformly less than 60% of the intensity displayed by their positive controls. The phenotypic traits of UVB-S and UVB-R appear, therefore, to be genetically determined. To that end, we provide in this report additional evidence that UVB-S is a polygenically determined trait that is dictated by polymorphisms at a locus within H-2, and at the Lps locus. Resistance to UVB radiation is a recessive trait, and requires homozygosity of resistance alleles at one or both of the two participating loci, whereas UVB-S acts as a dominant trait. Among H-2 congenic strains of mice that are lipopolysaccharide (LPS)-sensitive (Lpsn), UVB radiation impaired the induction of CH to DNFB in all mice except those of the H-2d and H-2a haplotypes. Thus, UVB-susceptibility is dictated by alleles at two, independent genetic loci that can influence transcriptional and translational activity of the Tnf-alpha gene. The potential biological and medical meaning of regulatory polymorphisms governing TNF-alpha production in the skin may be revealed by the recent demonstration that UVB-susceptibility and UVB-resistance are phenotypic traits in humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Studies of contact hypersensitivity induction in mice with optimal sensitizing doses of hapten

To avoid unsuspected and unwanted consequences of excess hapten during epicutaneous sensitization, optimal sensitizing doses of dinitrofluorobenzene (DNFB) were determined for several ultraviolet B radiation (UVB)-resistant and UVB-susceptible strains of mice. Using these doses of hapten applied epicutaneously or injected intracutaneously into normal or UVB-exposed body wall skin, it was determined that four consecutive daily exposures to UVB prevented contact hypersensitivity induction in all mice when optimal sensitizing doses of DNFB were applied epicutaneously. By contrast, UVB-resistant, but not UVB-susceptible, mice developed contact hypersensitivity when an optimal sensitizing dose of DNFB was injected intracutaneously into UVB-irradiated skin. Moreover, whereas UVB-susceptible mice failed to develop contact hypersensitivity when an optimal sensitizing dose of DNFB was painted on skin exposed to a single dose of UVB, UVB-resistant mice did develop contact hypersensitivity under similar circumstances. Based on these results, it is concluded that 1) conventional doses of epicutaneously applied haptens induce contact hypersensitivity with the aid of antigen-presenting cells derived from both the epidermis and the dermis, 2) the phenomenon of UVB susceptibility is mediated by cells and molecules within the dermis when conventional doses of hapten and UVB radiation are employed, and 3) UVB susceptibility is mediated by cells and molecules within the epidermis when optimal sensitizing doses of hapten and a single exposure to UVB are employed.

Tumor necrosis factor alpha polymorphism correlates with deleterious effects of ultraviolet B light on cutaneous immunity

Intradermally injected tumor necrosis factor alpha (TNF-alpha) mimics the effects of UV B light (UVB) radiation and neutralizing anti-TNF-alpha antibodies abolish the deleterious effects of UVB on induction of contact hypersensitivity suggesting that TNF-alpha is the major mediator of UVB effects on cutaneous immunity. In the present study we have shown that in lipopolysaccharide-sensitive inbred strains of mice, the ability of acute, low-dose UVB radiation to impair the induction of contact hypersensitivity to dinitrofluorobenzene is genetically determined by polymorphic alleles at the Tnf alpha locus. We have analyzed by the sequence analysis and restriction fragment length polymorphism the Tnf alpha alleles of numerous inbred strains expressing UVB susceptibility (UVB-S) and UVB-resistance (UVB-R). The Tnf alpha alleles of all UVB-R, but not UVB-S, strains contain a BamHI site in the first intron. Moreover, the 5' regulatory region of the Tnf alpha allele of UVB-R mice possesses a (CA)14 minirepeat that is located immediately 5' of the cytokine response element nearest the tumor-associated transplantation antigen box. By contrast, the Tnf alpha alleles of UVB-S mice display repeats of < > 14 at this site. It is proposed that the unique microsatellite of UVB-R mice impairs transcriptional efficiency at Tnf alpha compared to UVB-S mice and that the quantitative difference in Tnf alpha produced intracutaneously in response to UVB radiation accounts for the phenotypic traits of UVB-R and UVB-S.

IL-3 production as an in vitro marker of the genetically determined traits of UVB susceptibility and UVB resistance

The capacity of low-dose ultraviolet B (UVB) radiation to disrupt epidermal Langerhans cell function and to prevent the induction of contact hypersensitivity (CH) is genetically determined in mice and men. In mice, Tnf alpha and Lps are the genetic loci at which reside alleles that dictate susceptibility and resistance to the deleterious effect of UVB radiation. Detection of the UVB-susceptibility (UVB-S) and UVB-resistance (UVB-R) traits relies upon the in vivo end point of contact hypersensitivity, and is cumbersome, labor intensive, and time consuming. It has recently been reported that hapten-immune murine T cells can secrete interleukin-3 (IL-3) in vitro when exposed to hapten-derivatized syngeneic stimulator cells. To determine whether this assay might be useful in distinguishing UVB-R from UVB-S mice, panels of UVB-susceptible (C57BL/10, C3H/HeN) and UVB-resistant (A/J, BALB/c, C3H/HeJ) mice were sensitized epicutaneously with dinitrofluorobenzene (DNFB). When challenged in vitro 6 d later with dinitrophenyl-derivatized stimulator cells, T cells from all strains proliferated and secreted IL-3. Moreover, T cells from UVB-R mice that were sensitized through UVB-treated skin also made copious amounts of IL-3. However, T cells from UVB-S mice whose abdominal skin had been UVB irradiated prior to epicutaneous application of DNFB failed to secrete IL-3 in vitro, although the cells did proliferate. We conclude that following application of a sensitizing dose of hapten to UVB-exposed skin of UVB-S mice a) hapten-specific T cells are selectively unable to secrete IL-3 in vitro in response to hapten stimulation, and b) this inability is a reliable marker of the UVB-S trait. The IL-3 assay may prove useful in elucidating the mechanism by which UVB-exposed Langerhans cells activate regulatory T cells, and in detecting the UVB-S and UVB-R traits in humans.

Deleterious effects of cis-urocanic acid and UVB radiation on Langerhans cells and on induction of contact hypersensitivity are mediated by tumor necrosis factor-alpha

Ultraviolet B (UVB) light disrupts epidermal Langerhans cells (LC) universally and impairs the induction of contact hypersensitivity (CH) to epicutaneously applied haptens in certain strains of mice. Similar effects are observed when tumor necrosis factor-alpha (TNF alpha) is injected intradermally (ID) in mice. Trans-urocanic acid (UCA), a photoreceptor for UVB radiation, is known to be immunosuppressive. To determine whether cis-UCA is important in the process by which UVB and/or TNF alpha act in the skin, cis-UCA was injected ID into C57BL/6, C3H/HeN, BALB/c, and C3H/HeJ mice. Whole mounts of epidermis were removed 5 h later and stained immunochemically with anti-Ia antibodies. Microscopy revealed that Ia-bearing LC had lost their dendrites, had rounded up, and were reduced in number in all strains examined. Moreover, when dinitrofluorobenzene (DNFB) was applied epicutaneously to the injected site, induction of CH was grossly impaired. When neutralizing anti-TNF alpha antibodies were administered intraperitoneally 2 h prior to ID injection of cis-UCA, the deleterious effects on LC and CH induction were largely reversed. These results indicate that the actions of cis-UCA on LC and on CH induction are very similar to those achieved by ID injections of TNF alpha and by cutaneous exposure to low-dose UVB. Because the effects of UVB radiation and cis-UCA are reversed by anti-TNF alpha antibodies, we propose that UVB radiation impairs the induction of CH in mice by converting trans-UCA to cis-UCA within the epidermis; cis-UCA in turn causes the local release of TNF alpha, which thwarts sensitization by its ability to alter the functional program of epidermal Langerhans cells, thereby preventing the induction of CH.

Analysis of effects of ultraviolet B radiation on induction of primary allergic reactions

Acute, low-dose exposure to UVB light reveals a genetic polymorphism in humans with respect to the ability of irradiated skin to support the induction of contact hypersensitivity (CH) to dinitrochlorobenzene (DNCB). In healthy adult caucasians, as well as in humans with deeply pigmented skin, approximately 45% fail to develop CH when DNCB is painted on UVB-irradiated skin; these individuals are termed "UVB susceptible" (UVB-S), whereas those who develop CH at the challenge site are termed "UVB resistant" (UVB-R). The UVB-S trait is characteristic of virtually all patients with biopsy-proved basal/squamous cell cancer, and may therefore be a risk factor for this disease. We have investigated the effects of UVB on expression of primary allergic reactions (PAR) in healthy caucasian and black-skinned adults, as well as patients with skin cancer. Among UVB-R caucasians, very few (less than 25%) developed PAR at site exposed to UVB, whereas among black-skinned UVB-R subjects, all displayed a PAR at the UVB irradiated site. To determine whether the lack of PAR in UVB-R caucasian subjects was systemic or local in origin, DNCB was applied to UVB-exposed buttock skin, and each individual was then challenged with dilute DNCB on forearm skin twice: 11 and 30 d thereafter. When inflammatory responses were evaluated at the original hapten application site, as well as both challenge sites, complete concordance was observed between positive challenge reactions at 30 d (UVB-R) and positive challenge reactions at 11 d, whereas only one caucasian subject displayed a PAR at 12 d. Thus, UVB-R caucasians can display CH as early as 11 d following hapten application to UVB-treated skin, indicating that their failure to display PAR is a local, rather than a systemic, effect of UVB. Because UVB-induced phototoxicity was significantly greater in caucasian than in deeply pigmented skin, it is anticipated that phototoxicity leads to rapid hapten "washout" from UVB-exposed caucasian skin. We propose that PAR usually do not occur in UVB-treated caucasian skin because insufficient hapten remains at the site to trigger a spontaneous inflammation when systemic hapten-specific immunity emerges.

Tumour necrosis factor-alpha mediates ultraviolet light B-enhanced expression of contact hypersensitivity

Acute, low-dose ultraviolet B radiation (UVB) impairs the induction of contact hypersensitivity (CH) to dinitrochlorobenzene (DNCB) in certain inbred strains of mice (termed UVB-susceptible), but not in others (termed UVB-resistant). By contrast, exposure of mouse ear skin to an identical regimen of UVB has been reported to exaggerate the expression of CH. Recently, tumour necrosis factor-alpha (TNF-alpha) has been demonstrated to mediate the deleterious effects of UVB on CH induction, presumably through local release of TNF-alpha within UVB exposed skin. The present studies were conducted to determine whether TNF-alpha also mediates the exaggerated expression of CH induced by UVB radiation. It was found that TNF-alpha, injected intradermally at the ear challenge site, enhanced the expression of CH to DNFB in conventionally sensitized mice. Interestingly, TNF-alpha was able to amplify the expression of CH in the ears of both UVB-susceptible strains of mice, and UVB-resistant strains. However, anti-TNF-alpha antibodies neutralized UVB-enhanced CH in UVB-susceptible mice, but not in UVB-resistant mice. These findings support the proposition that TNF-alpha, released from UVB-exposed epidermal cells, is a critical mediator of the effects of UVB radiation on induction and expression of contact hypersensitivity. The effects of UVB radiation, intradermal (ID) TNF-alpha, and/or epicutaneously applied DNFB on epidermal Langerhans' cells were also evaluated and compared. Whereas epicutaneously applied DNFB alone profoundly depleted the epidermis of Langerhans' cells, DNFB painted on UVB-exposed or TNF-alpha-treated skin was much less effective at eliminating normal appearing Langerhans' cells. These results suggest that one direct effect of TNF-alpha on Langerhans' cells may be to immobilize these antigen-presenting cells transiently within the epidermis. It is proposed that this immobilization has the paradoxical effect (a) of interfering with sensitization, by preventing hapten-bearing Langerhans' cells from migrating to the draining lymph node, while at the same time (b) of amplifying CH expression by lengthening the interval of hapten retention and presentation with the epidermis.

cis-urocanic acid suppression of contact hypersensitivity induction is mediated via tumor necrosis factor-alpha

Ultraviolet B (UVB) light impairs the induction of contact hypersensitivity to epicutaneously applied haptens in certain strains of mice by a genetically determined mechanism that depends upon the participation of TNF-alpha. Because the superficial epidermis contains large amounts of trans-urocanic acid (trans-UCA), because exposure to UVB radiation converts this compound to cis-UCA, and because cis-UCA has been reported to be immunosuppressive, we have examined the possibility that the TNF-alpha-dependent effects of UVB on contact hypersensitivity induction in mice are mediated via conversion of trans- to cis-UCA. By injecting cis-UCA intradermally before application of dinitrofluorobenzene, by treating cis-UCA-injected mice systemically with neutralizing anti-TNF-alpha antibodies, and by comparing the consequences of these maneuvers in UVB-susceptible and UVB-resistant strains of mice, we have determined a) that cis-UCA can impair the induction of contact hypersensitivity in a manner similar to UVB radiation, and that the impairment is dependent upon TNF-alpha; b) that cis-UCA altered the morphology of epidermal Langerhans cells in a manner similar to UVB radiation, and that the alteration was dependent, in part, upon TNF-alpha; and c) that the inhibitory effects of cis-UCA on induction of contact hypersensitivity and the histologic effects of this compound on epidermal Langerhans cells appear to be influenced by alleles at the Tnf alpha and Lps loci. Based on these findings we propose that UVB radiation impairs the induction of contact hypersensitivity in mice by converting trans-urocanic acid to cis-UCA within the epidermis; cis-UCA in turn causes the local release of TNF-alpha, which thwarts sensitization by its ability to trap epidermal Langerhans cells transiently within the epidermis, and thereby prevents the immunogenic signal from reaching the draining lymph node where activation of unprimed, Ag-specific T cells must occur.

cis-urocanic acid suppression of contact hypersensitivity induction is mediated via tumor necrosis factor-alpha

Ultraviolet B (UVB) light impairs the induction of contact hypersensitivity to epicutaneously applied haptens in certain strains of mice by a genetically determined mechanism that depends upon the participation of TNF-alpha. Because the superficial epidermis contains large amounts of trans-urocanic acid (trans-UCA), because exposure to UVB radiation converts this compound to cis-UCA, and because cis-UCA has been reported to be immunosuppressive, we have examined the possibility that the TNF-alpha-dependent effects of UVB on contact hypersensitivity induction in mice are mediated via conversion of trans- to cis-UCA. By injecting cis-UCA intradermally before application of dinitrofluorobenzene, by treating cis-UCA-injected mice systemically with neutralizing anti-TNF-alpha antibodies, and by comparing the consequences of these maneuvers in UVB-susceptible and UVB-resistant strains of mice, we have determined a) that cis-UCA can impair the induction of contact hypersensitivity in a manner similar to UVB radiation, and that the impairment is dependent upon TNF-alpha; b) that cis-UCA altered the morphology of epidermal Langerhans cells in a manner similar to UVB radiation, and that the alteration was dependent, in part, upon TNF-alpha; and c) that the inhibitory effects of cis-UCA on induction of contact hypersensitivity and the histologic effects of this compound on epidermal Langerhans cells appear to be influenced by alleles at the Tnf alpha and Lps loci. Based on these findings we propose that UVB radiation impairs the induction of contact hypersensitivity in mice by converting trans-urocanic acid to cis-UCA within the epidermis; cis-UCA in turn causes the local release of TNF-alpha, which thwarts sensitization by its ability to trap epidermal Langerhans cells transiently within the epidermis, and thereby prevents the immunogenic signal from reaching the draining lymph node where activation of unprimed, Ag-specific T cells must occur.