Atopic dermatitis: introduction and overview.
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Dermatitis, Atopic↗
Biomedical subjects
K D Cooper
Publications and source records attributed to K D Cooper.
Monocyte induction of IL-10 and down-regulation of IL-12 by iC3b deposited in ultraviolet-exposed human skin.
CD11b+ monocytic/macrophagic cells (Mo/Mph), which infiltrate into skin after UV irradiation, play an important role in UV-induced immunosuppression. Because in mice, blockade of CD11b (iC3b receptor) on monocytes and depletion of its ligand, iC3b, reverses UV-induced immunosuppression, we asked whether iC3b is deposited in human skin after UV, and whether iC3b can modulate the cytokine profile of Mo/Mph. Immunofluorescence studies revealed that iC3b was newly deposited in UV-exposed skin and was localized in apposition to infiltrating CD11b+ Mo/Mph. In addition, in situ hybridization studies showed that TNF-alpha mRNA was also induced in a similar microanatomic localization. To model the effects of these complex signals on infiltrating Mo/Mph following UV exposure, we then tested the effects of immobilized iC3b and TNF-alpha on resting blood monocytes. Both IL-10 mRNA synthesis and protein secretion were significantly induced by binding of iC3b in vitro and were synergistically increased by the presence of TNF-alpha. The effect was abrogated by a blocking Ab to CD11b, indicating CD11b-iC3b interaction. In contrast, iC3b binding resulted in suppression of IL-12 p40 mRNA and significantly inhibited the production of IL-12 p70 protein. Our studies thus define a novel mechanism for induction of tissue Mo/Mph into an IL-10high/IL-12low state via iC3b in combination with TNF-alpha.
Adult↗
Activated complement component 3 (C3) is required for ultraviolet induction of immunosuppression and antigenic tolerance.
Complement component 3 (C3), a critical regulator of innate immunity, may also play a role in the regulation of cognate immunity, such as contact sensitivity responses. Because ultraviolet (UV) radiation also activates C3 in the skin, we determined whether the immunosuppressed state that results when a contact sensitizer is applied through UVB-exposed skin requires the presence and activation of C3. This question was addressed through the use of C3-deficient mice, blockade of C3 cleavage to C3b, and accelerated degradation of iC3b by soluble complement receptor 1 (sCR1). Both C3-modulated systems totally reversed the failure to induce a contact sensitivity response to dinitrofluorobenzene (DNFB) upon primary sensitization at the UV-exposed site, as well as immunologic tolerance to a second DNFB immunization through normal skin. Treatment with sCR1 reduced the infiltration of CD11b+ leukocytes into the epidermis and dermis of UV-irradiated skin but did not reverse the UV-induced depletion of epidermal class II MHC+CD11blo Langerhans cells. These data, taken together with previous results showing abrogation of locally induced UV immunosuppression by in vivo anti-CD11b treatment, suggest a novel mechanism by which ligation of the leukocyte beta2 integrin, CD11b, by iC3b molecules formed from C3 activation in UV-exposed skin, modifies cutaneous CD11b+ cells such that skin antigen-presenting cells are unable to sensitize in a primary immune response, but actively induce antigenic tolerance.
Animals↗
Fibronectin and alpha5 integrin regulate keratinocyte cell cycling. A mechanism for increased fibronectin potentiation of T cell lymphokine-driven keratinocyte hyperproliferation in psoriasis.
In addition to being T lymphocyte-driven, psoriasis may be due in part to abnormal integrin expression. Normal-appearing (uninvolved) skin from psoriatic patients was examined to determine whether altered fibronectin or its receptor expression is detectable before development of psoriatic lesions. In contrast to skin from normal subjects, we detect by immunofluorescence the abnormal presence of plasma fibronectin in the basal cell layer of the epidermis of psoriatic uninvolved skin. Furthermore, increased fibronectin exposure superinduces the in vitro cell cycle induction and expansion of psoriatic nonlesional keratinocytes in response to a cocktail of T cell lymphokines. Fibronectin alone also appeared to increase cell cycle entry among uninvolved but not normal keratinocytes. Concordantly, the alpha5 integrin fibronectin receptor, but not alpha2 or alpha3, is overexpressed in the in vivo nonlesional psoriatic epidermis. The involvement of alpha5beta1 in the early outgrowth of clonogenic keratinocytes in the ex vivo culture was demonstrated by the ability of anti-alpha5 mAb to inhibit keratinocyte growth on fibronectin. Thus, the fibronectin receptor appears to be one of the components required for the development of the hyperresponsiveness of psoriatic keratinocytes to signals for proliferation provided by lymphokines produced by intralesional T lymphocytes in psoriasis.
Antigens, CD↗
Long-term effectiveness and safety of recombinant human interferon gamma therapy for atopic dermatitis despite unchanged serum IgE levels.
OBJECTIVE: To assess the long-term effects of recombinant human interferon gamma treatment of atopic dermatitis (AD). DESIGN: Case series. Patients were treated for up to 24 months. SETTING: University dermatology outpatient clinics in Ann Arbor, Mich, and Portland, Ore. PATIENTS: Twenty-four of 32 eligible patients who participated in a previously reported, 12-week, double-blind, placebo-controlled study of recombinant human interferon gamma treatment for AD were enrolled. INTERVENTION: Patients self-administered recombinant human interferon gamma, 50 microg/m2, by daily subcutaneous injection. MAIN OUTCOME MEASURES: Overall response; body surface area of involvement; clinical severity scores for pruritus, erythema, edema, excoriations, dryness, scaling, and lichenification; other atopic symptoms; and laboratory parameters, including serum IgE levels, were monitored at quarterly visits. Results at 1 and 2 years were compared with baseline values. RESULTS: All efficacy parameters improved (P<.05). For example, pruritus was reduced by 50% after both 1 (n=24, P<.001) and 2 (n=16, P=.005) years. Allergic conjunctivitis and allergic rhinitis also improved (P<.01). Eosinophil counts decreased significantly (P<.001). IgE levels increased. Clinical improvement more closely correlated with changes in eosinophil counts (r=0.3-0.5) than with changes in IgE levels (r=0.0-0.2). Only 1 patient discontinued therapy because of adverse effects (flulike symptoms). CONCLUSIONS: The initial efficacy and adverse effects reported for recombinant human interferon gamma treatment of patients with AD were maintained after 2 years of long-term use. Recombinant human interferon gamma seems to be a well-tolerated and effective agent in the long-term therapy of patients with AD. Therapies that correct cellular immune defects, but not humoral immune defects, may be effective in the treatment of patients with AD.
Adolescent↗
Low expression of CD40 and B7 on macrophages infiltrating UV-exposed human skin; role in IL-2Ralpha-T cell activation.
After UV exposure of skin, epidermal Langerhans cells (LC) are depleted, whereas CD11b+CD36 CD1a- monocytes/macrophages (UV-Mphi) infiltrate. Different immunological outcomes in vivo are mediated by LC (sensitization) and UV-Mphi (tolerance) which may be related to the distinct T cell activation states that these antigen-presenting cells (APC) induce. We previously demonstrated that CD4+ T lymphocytes activated by UV-Mphi are, in contrast to LC-activated T cells, IL-2Ralpha deficient, and we hypothesize that this differential T cell activation is related to differences in co-stimulatory molecules between UV-Mphi and LC. Using four-color flow cytometry, we found a reduced capacity to up-regulate expression of the important co-stimulatory molecules CD40, B7-1 and B7-2 by UV-Mphi relative to LC. This alteration in co-stimulatory molecule expression was selective, because UV-Mphi express equal levels of ICAM-1 and ICAM-3, and increased levels of LFA-1, relative to LC. After bidirectional signaling with T cells during alloantigen presentation, UV-Mphi still exhibited less CD40 and B7-1 than LC. Addition of IFN-gamma induced CD40 and B7-1 expression on UV-Mphi and restored IL-2Ralpha expression on UV-Mphi-activated T cells but had no effect on IL-2Ralpha on resting or LC-activated T cells. The restoration of IL-2Ralpha expression on UV-Mphi-activated T cells by IFN-gamma was inhibited (67 %, p = 0.005) by addition of neutralizing anti-CD40. Therefore, differences in co-stimulatory molecule expression, in particular CD40, on UV-Mphi and LC are critical in determining the distinct T cell activation induced by these APC.
B7-1 Antigen↗
IL-1 and IL-1 receptor antagonist regulation during keratinocyte cell cycle and differentiation in normal and psoriatic epidermis.
Changes in the levels of IL-1 (IL-1alpha, IL-1beta, and its receptor antagonist, IL-1RA) occur upon keratinocyte differentiation in vitro and are associated in vivo with abnormal differentiated and hyperproliferative states of psoriatic keratinocytes. A flow cytometric procedure, capable of detecting changes in the intracellular levels of IL-1, was used to determine whether intracellular IL-1/IL-1RA levels in psoriatic and normal keratinocytes alter during in vivo differentiation and the cell cycle. Increases in the IL-1RA levels and IL-1alpha levels were observed as both normal and psoriatic keratinocytes differentiated from basal stem cells (beta1 integrin+, small size) into transient amplifying cells (TAC; beta1 integrin+, large size). Upon further differentiation (beta1 integrin-, large size) both IL-1RA and IL-1alpha levels dropped. However, while psoriatic IL-1beta levels increased as cells differentiated into TACs, little change occurred in the IL-1beta levels of normal keratinocytes during differentiation. Changes in IL-1/IL-1RA levels were also detected as keratinocytes progressed through the cell cycle. Within the basal stem cell population of both normal and psoriatic keratinocytes, the IL-1alpha and IL-1RA levels increased between G0/G1 and S but not between S and G2/M. However, psoriatic basal keratinocyte IL-1beta levels differed from those of normal keratinocytes by showing no increase between S and G2/M. The IL-1/IL-1RA levels of normal TAC increased throughout the cell cycle. However, in psoriatic TAC, a slight decrease in IL-1alpha and IL-1RA levels was observed between G0/G1 and S followed by a delayed increase between S and G2/M. IL-1beta levels in psoriatic TAC varied little throughout the cell cycle. Thus, we were able to detect precisely the regulation of IL-1/IL-1RA intracellular levels during the keratinocyte cell cycle and differentiation, showing notably decreased IL-1beta upregulation in psoriatic keratinocytes progressing through the cell cycle.
Cell Cycle↗
In human skin, UVB initiates early induction of IL-10 over IL-12 preferentially in the expanding dermal monocytic/macrophagic population.
In contrast to Langerhans cells, which make interleukin (IL)-12, differentiated macrophages that infiltrate the epidermis 72 h after ultraviolet B (UV) irradiation potently produce IL-10 mRNA and secrete IL-10 protein. We asked whether differentiated UV macrophages in the epidermis acquired their activated, IL-10hi status as a result of entering the epidermis or as a result of encountering UV-induced changes in the dermal microenvironment. In this study, sequential section immunostaining directly showed dynamic and reciprocal changes of infiltrating CD11b+ macrophages and CD1a+ Langerhans cell loss in human epidermis and dermis after in vivo UV exposure in relation to the microanatomic localization of newly appearing dermal cells that stain for IL-10 mRNA by in situ hybridization. Using quantitative reverse transcriptase polymerase chain reaction on purified dermal cell subsets, the first significant rise in IL-10 mRNA occurred 6 h after UV in the dermal CD11b+ (CD1-, 3-, 24-, 56-) monocytic/macrophagic population. Significant induction of IL-10 mRNA 24 h post-UV was limited to the CD11b+ CD1- subset (p = 0.006). The fold increase of IL-10 mRNA relative to 0 h by the CD11b+ dermal monocytic/macrophagic population peaked at 24-48 h and tapered thereafter. Intense IL-10 production by macrophages in the epidermis appeared to follow dermal changes, with maximum production at 72 h, indicating migration/activation of this population from the dermis, and the remainder of dermal cells, depleted of monocyte/macrophages and Langerhans cell-like antigen-presenting cells, showed no increase in IL-10 at any time point post-UV. IL-10 protein-producing CD11b+ macrophages in the dermis were also documented by flow cytometry. IL-12 mRNA was differentially regulated from IL-10 after UV, in that IL-12 was consistently downregulated in the CD11b+ monocytic/macrophagic population (p < 0.0002). Taken together, monocytic/macrophagic cells with high IL-10 and low IL-12 expression initially appear in the dermis as early as 6 h, and then appear in the epidermis, implicating the dermis as the primary site of activation/signaling for IL-10 upregulation in cutaneous antigen-presenting cells.
Adult↗
The human hair follicle: a reservoir of CD40+ B7-deficient Langerhans cells that repopulate epidermis after UVB exposure.
The ability of skin to maintain its protective structural and functional integrity depends on both resident and circulating cells. Until now, it was thought that dendritic antigen presenting cells of epidermis (Langerhans cells) were replaced by circulating bone marrow derived precursors. Here we show by immunostaining studies of timed biopsies taken from human skin after ultraviolet exposure, that hair follicle is a critical reservoir of Langerhans cells that repopulate epidermis depleted of Langerhans cells by a single four minimal erythema dose of ultraviolet B. Immunostaining with antibodies to thymidine dimers showed that ultraviolet B only penetrated the superficial hair follicle opening, whereas deeper follicle was relatively protected. Langerhans cells migrating from hair follicle into epidermis 72 h after ultraviolet exposure have a partial deficiency of molecules important to T cell costimulation. We used four color flow cytometry to show that Langerhans cells isolated from epidermis 72 h after ultraviolet B can upregulate CD40 but not B7-1 or B7-2 expression in culture, suggesting a different phenotype of hair follicle Langerhans cells. Therefore, the hair follicle is a specialized immune compartment of the skin that serves as an intermediate reservoir of Langerhans cells between bone marrow and epidermis, and that may play a critical role in immune surveillance.
B7-1 Antigen↗
Identification and quantitation of interferon-gamma producing T cells in psoriatic lesions: localization to both CD4+ and CD8+ subsets.
Interferon-gamma (IFN-gamma) produced by lesional T cell clones is critical for the induction into G1 of the cell cycle by psoriatic keratinocyte stem cells; however, direct data demonstrating psoriatic lesional T cell subset IFN-gamma expression, and quantitation at a single cell level to calculate in vivo proportions, are lacking. In this study, using flow cytometry of freshly isolated normal and psoriatic lesional T cells from keratome biopsies, we found elevated CD3+, CD4+, and CD8+ T cells in all compartments of psoriatic skin, compared with normals. Using Brefeldin A to induce short-term intracellular accumulation of IFN-gamma in T cells capable of IFN-gamma production, we found that 90% of psoriatic patients have IFN-gamma-producing T cells at a greater proportion of their CD3+ cells than normals, with a mean of 16%+/-3%, as compared with 4%+/-2% in normal epidermis (p = 0.01). Expressed as density in the tissue, the IFN-gamma+ CD3+ cell number in psoriatic epidermis was 97+/-22 per mm2 surface area, as compared with 4.4+/-1.8 per mm2 of normal epidermis (p = 0.002). Thus, the total number of IFN-gamma+CD3+ T cells in the skin of a patient with 20% involvement is estimated to be 3.9 x 10(8). CD4+ and CD8+ IFN-gamma+ T cells were both elevated in psoriatic epidermis (p = 0.04 and p = 0.008, respectively) relative to normal skin. In the dermis, only 44% of patients demonstrated a higher percentage of IFN-gamma-producing T cells than did normals (p = 0.1), possibly indicating dilution, in some patients, by fresh infiltrating T cells. Interleukin-4 was not found by a combination of flow cytometry, reverse transcriptase-polymerase chain reaction, western blot, and immunoprecipitation. In conclusion, a significant portion of lesional T cells in psoriasis are IFN-gamma producing, without interleukin-4. The increased numbers of both IFN-gamma+CD4+ and IFN-gamma+CD8+ T cells indicate that both CD4+ and CD8+ IFN-gamma+ T cells are present in appropriate anatomic locations to sustain the lesional pathology.
Adult↗
Rapamycin (sirolimus) inhibits proliferating cell nuclear antigen expression and blocks cell cycle in the G1 phase in human keratinocyte stem cells.
Because the immunosuppressant rapamycin (sirolimus) blocks T cell proliferation in G1 phase, it has been proposed as a potential treatment for psoriasis, a skin disease characterized by T cell activation and keratinocyte stem cell hyperproliferation. To determine another potentially important mechanism through which rapamycin can act as an antipsoriatic agent, we tested its direct effect on keratinocyte stem cell proliferation in vitro as well as in vivo. In vivo cell cycle quiescent (G0 phase) stem cell keratinocytes in primary culture sequentially express de novo cyclin D1 and proliferating cell nuclear antigen (PCNA), prior to S phase entry, and upregulate beta1 integrin. Rapamycin inhibited the growth of keratinocytes that were leaving quiescence as well as those already in cell cycle without affecting cell viability. Although beta1 integrin(bright) expression was not affected, the number of beta1 integrin(bright) cells entering S/G2/M was significantly lowered by rapamycin. Cells treated with rapamycin exhibited decreased PCNA expression while cyclin D1 expression, which precedes PCNA expression in the cell cycle, was not affected. We found similar effects on stem cell keratinocytes in patients with psoriasis treated systemically with rapamycin. Because PCNA is required for cell cycle progression from G1 to S phase, our data indicate that inhibition of PCNA protein synthesis may be an important regulatory element in the ability of rapamycin to exert a G1 block.
Cells, Cultured↗
Significantly increased occurrence of HLA-DQB1*0301 allele in patients with ocular cicatricial pemphigoid.
To determine the immunogenetic characteristics of patients with immune-mediated subepithelial blistering diseases of mucous membranes, we performed HLA-typing for the class II MHC gene DQB1*0301 allele using a direct method. Genomic DNA extracted from Caucasian patients was amplified by polymerase chain reaction using primer pairs specific for the DQB loci followed by Southern blotting with a peroxidase-conjugated sequence-specific oligonucleotide probe. Seventy-six percent (16/21) of patients with ocular mucosal disease (with or without oral mucosal and skin diseases) carried the DQB1*0301 allele; by contrast, only 33% (14/42) of race-, age-, and geography-matched normal individuals carried the DQB1*0301 allele (p < 0.005). The relative risk for ocular disease if DQB1*0301 allele is present is 6.4, similar to the relative risk of 8 for patients with ocular but no oral disease (pure ocular cicatricial pemphigoid, p < 0.025). In patients with oral mucosal disease (with or without ocular mucosal and skin diseases), 68% (15/22) carried the DQB1*0301 allele (p < 0.025). When patients with ocular disease were excluded, however, the increased occurrence of the DQB1*0301 allele in patients with oral disease was not statistically significant (64%, 7/11, p < 0.25). In patients with subepidermal blistering skin disease but no oral or ocular disease, there was no increase in the occurrence of the DQB1*0301 allele (38%, 5/13, p > 0.5). The significantly increased occurrence of the DQB1*0301 allele in patients with ocular mucosal disease may point to a distinct immunogenetic factor that predisposes patients to develop an ocular scarring process.
Alleles↗
UVA II exposure of human skin results in decreased immunization capacity, increased induction of tolerance and a unique pattern of epidermal antigen-presenting cell alteration.
The risks incurred from increased exposure to UVA II (320-340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon are lamp filtered with a narrow bandpass filter (335 +/- 5 nm full width at half maximum), individuals were contact-sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II-exposed group, as compared to 3.8% in the controls (P = 0.006). UVA II also uniquely altered the type of antigen-presenting cells present in the epidermis. Human leukocyte antigen (HLA)-DR+ cells in control epidermal cell suspensions (C-EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1ahi DRmid CD11b CD36 (1.5 +/- 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 +/- 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a- DRhi CD11b+ CD36+ were increased in UVA II skin, relative to C-EC, these comprised only 10.1 +/- 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II-EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CD11b+; these comprised 11.1 +/- 6.9% of the DR+ UVA II-EC. In conclusion, despite the above differences in infiltrating DR+ cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.
Adaptation, Physiological↗
Lesional psoriatic T cells contain the capacity to induce a T cell activation molecule CDw60 on normal keratinocytes.
In this report we demonstrate, that in psoriatic skin, basal and suprabasal keratinocytes express CDw60. The CDw60-specific monoclonal antibody, UM4D4, has recently been shown to recognize the 9-O-acetylated disialosyl group on ganglioside GD3. The CDw60 antigen on cultured keratinocytes also seems to be identical with the 9-O-acetylated disialosyl group, because the anti-UM4D4 binding was markedly reduced after neuraminidase treatment of keratinocytes. To examine whether factors from T cells in psoriatic lesions are responsible for the overexpression of CDw60 on keratinocytes, T cell lines obtained from lesional skin were initiated and cloned by limiting dilution. Factors released from 19 of 19 activated T cell clones up-regulated CDw60 expression on cultured normal keratinocytes. T-cell-secreted cytokines, including interleukin (IL)-2, IL-3, IL-4, IL-6, IL-13, transforming growth factor-beta, granulocyte/macrophage colony-stimulating factor, and interferon-gamma were tested for their capacity to modulate keratinocyte CDw60 expression. IL-4 and IL-13 strongly up-regulated the expression of CDw60; by contrast, interferon-gamma down-regulated keratinocyte CDw60 expression. Interestingly, IL-13 may in part be responsible for the T-cell-induced up-regulation of CDw60, because anti-IL-13 partly neutralized this effect of the T cell supernatant. In conclusion, CDw60 expression on psoriatic epidermal keratinocytes is likely induced by intralesionally activated T cells and may in part be due to IL-13. These findings would represent a novel mechanism by which T cells participate in the pathogenesis of psoriasis.
Antibodies↗
Reversal of immunosuppression inducible through ultraviolet-exposed skin by in vivo anti-CD11b treatment.
In both human in vitro models and murine in vivo adoptive transfer studies, UV-induced class II MHC+ CD11b+ leukocytes that infiltrate the epidermis appear to mediate UV-induced immunosuppression. In the present study, their role is further probed using an anti-CD11b mAb (clone 5C6), which is effective in vivo in blocking CD11b+ monocyte/macrophage diapedesis into inflammatory lesions. A single exposure, low dose UV protocol (72 mJ/cm2) that resulted in tolerance only when dinitroflurobenzene was applied 48 h later through the UV-irradiated skin, but not through a distant non-UV-irradiated site, was used. In vivo anti-CD11b treatment in non-UV-irradiated mice did not block contact sensitivity responses. However, the ability to induce a primary contact sensitivity response was completely restored in UV-irradiated mice receiving anti-CD11b. This restoration was associated with partial restoration of papillary dermal class II MHC+ NLDC-145- cells. In vivo anti-CD11b treatment also blocked tolerance induction, which was associated with a 50% reduction in the infiltration of class II MHC+ CD11b+ Gr-1+ monocyte/macrophages into UV-irradiated skin. In addition, anti-CD11b treatment partially protected against epidermal UV injury, in that the epidermal structure was better preserved and the keratinocytes were less severely damaged. CD11b+ leukocytes may thus affect UV-irradiated skin through at least two mechanisms: 1) a class II MHC+ CD11b+ Gr-1+ monocyte/macrophage population inducing a state of tolerance to Ag(s) acquired in UV-irradiated skin, and 2) CD11b+ leukocytes capable of inflicting additional injury to both keratinocytes and constitutive APC damaged by UV photons.
Animals↗
IL-12 synthesis by human Langerhans cells.
IL-12 is a 70-kDa heterodimeric cytokine composed of a p35 chain and p40 chain. This cytokine exerts a powerful positive regulatory influence on the development of Th1 helper T-cell immune responses and is a potent inducer of IFN-gamma production and cytotoxic T cell differentiation and function. Because epidermal Langerhans cells (LC) are important members of the dendritic APC lineage family critical for initiating cell mediated immune responses, we examined LC for their ability to produce IL-12. Epidermal cell (EC) suspensions obtained from volunteers were enriched for, or depleted of, Langerhans cells (CD1a+ EC). Enriched populations contained > 90% CD1a+ cells, whereas depleted populations contained < 1% CD1a+ cells. As assessed by reverse transcription-PCR amplification, IL-12 p40 mRNA was constitutively expressed in LC RNA extracted immediately following keratome harvest, and increased spontaneously after overnight incubation. Radioimmunoassay (RIA) of IL-12 p40 protein on supernatants revealed IL-12 release by CD1a-enriched fractions of epidermal cells. Ab specific for p40 clearly demonstrated IL-12 in epidermal LC by flow cytometry. A bioassay for the functional IL-12 heterodimer (p70) indicated that LC could produce IL-12 biologic activity, which was neutralized by anti-IL-12 Ab. These results indicate that epidermal LC, in particular cultured LC maturing into dendritic cells, express IL-12 p40 mRNA, as well as p40 and functional p70 protein, and suggest that this is one mechanism behind the high potency of dendritic APCs, such as LC, to initiate Th1 type immune responses under appropriate conditions.
Adult↗
In vivo retinoic acid modulates expression of the class II major histocompatibility complex and function of antigen-presenting macrophages and keratinocytes in ultraviolet-exposed human skin.
UNLABELLED: Because retinoic acid (RA) can alter photoaging of the skin and repeated ultraviolet (UV)-induced immunologic injury may play a role in chronic photoaging, we asked whether RA alters the acute photoimmunologic effects of UV radiation. Two sites from each volunteer were treated with 0.1% RA or vehicle continuously for 24 h before and 24 h after a 4-minimal erythema dose UVB exposure. RA did not function as a sunscreen, as determined by quantitating the increase in redness after 1 minimal erythema dose to vehicle- and RA-pretreated sites (n = 12). By flow cytometric analysis of epidermal cell suspensions harvested 3 d after the UV-EC, RA treatment did not protect CD1+ Langerhans cells from being depleted by UV light and did not modify the number of UV-induced infiltrating CD36+CD11b+CD1-DR+ macrophages. RA treatment did, however, result in a 40% downregulation of human leukocyte antigen (HLA)-DR expression on these infiltrating macrophages (p = 0.016) (n = 11), in conjunction with a decrease in alloantigen-presenting cell activity of RA-treated UV-EC as measured by T-cell proliferations. RA also induced a 72% inhibition of the autologous T suppressor-inducer cell proliferation induced by UV-EC (vehicle: 21,813 +/- 7,302 cpm; RA; 5,299 +/-635 cpm) (n = 3). The downregulation could be due to RA-modulated keratinocytes; RA-treated UV-EC keratinocytes depleted of CD1a+ and DR+ antigen-presenting cells displayed a greater ability, relative to similarly treated vehicle-EC keratinocytes, to inhibit alloantigen presentation. IN CONCLUSION: (i) in vivo RA treatment did not protect human Langerhans cells from being depleted by UV and did not block infiltration of macrophages into sunburned skin; and (ii) RA did decrease autologous and allogeneic T-cell reactivity induced by macrophage antigen-presenting cells in UV-exposed epidermis, at least in part by downregulating their HLA-DR expression and by upregulating inhibitory signals from UV-irradiated keratinocytes.
Adult↗
Identification of a human dermal macrophage population responsible for constitutive restraint of primary dermal fibroblast proliferation.
Primary human dermal cell suspensions prepared from the papillary dermis of keratomed skin strips were used to investigate the effect of indigenous dermal macrophages (HLA-DR+, CD11c+ CD11b+ CD1c- phagolysosome+) upon dermal fibroblast proliferation. Rapid dermal fibroblast expansion was induced upon immunomagnetic bead removal of CD11b+ or CD11c+ cells as well as by removal of more inclusive subsets contained within the DR+ population, but the removal of mast cells, endothelial cells, and CD1c+ dermal Langerhans cells from dermal cell suspensions failed to result in proliferation of the remaining cell subsets. Removal of 1B10+ fibroblasts from macrophage depleted (CD11b-) dermal cell suspensions essentially abrogated the unrestrained proliferation of the CD11b- dermal cells. Flow cytometric cell cycle analysis of cultured macrophage-depleted dermal cells confirmed that the unrestrained proliferating cells contain procollagen I+ as well as procollagen I- dermal fibroblasts. Inhibition of primary fibroblast expansion by adding a supernatant from unfractionated dermal cells suggested that a growth-inhibitory soluble activity of >30,000 kDa dominates the cytokine mixture released by unfractionated fresh dermal cells ex vivo. Inhibitory activity counterbalanced positive fibroblast growth- stimulatory cytokines released by dermal cells because neutralizing antibodies to insulin-like growth factor 1 and interleukin-1 beta resulted in decreased CD11b- dermal cell fibroblast proliferation. These data indicated an important role for dermal macrophages of the DR+ CD11b+ CD11c+ DC1c- phenotype in the normal homeostatic restraint of primary human dermal fibroblast proliferation.
Adult↗