Peripheral natural killer cells exhibit qualitative and quantitative changes in patients with psoriasis and atopic dermatitis.

BACKGROUND: Psoriasis and atopic dermatitis are the most recurrent skin inflammatory disorders. Despite their distinct aetiology and clinical aspects, these diseases share several immunological features. Besides the largely documented role of T cells, emerging literature supports a potential involvement of innate immune effectors, the natural killer (NK) cells, in both pathologies. In the peripheral blood, NK cells consist of CD3-CD56dim and CD3-CD56bright cell subsets, harbouring a distinct cell surface phenotype, but both endowed with the main NK-cell effector functions: cytotoxicity and cytokine production. OBJECTIVES: To determine whether the frequency, the cell surface phenotype and the functional properties of peripheral NK cells were affected in patients with psoriasis or atopic dermatitis. METHODS: Peripheral blood mononuclear cells were isolated from 11 patients with psoriasis, nine patients with atopic dermatitis and 16 healthy individuals. By using flow cytometry, we analysed the following parameters of peripheral NK cells: the frequency, the cell surface expression of several NK-cell receptors (NKR) and the activation of the effector functions upon various in vitro stimuli. RESULTS: Peripheral NK cells were significantly reduced in both skin diseases. The cell surface expression of various NKR was differently modified in peripheral NK cells of the two cohorts of patients. Finally, NK-cell natural cytotoxicity was affected only in atopic dermatitis, while interferon-γ production was defective in both groups of patients. CONCLUSION: Psoriasis and atopic dermatitis are associated with quantitative and qualitative changes of peripheral NK cells, mostly shared by both diseases, supporting a common process implicating these innate effectors in skin inflammation.

Clinical evaluation of corneal epithelialization after photorefractive keratectomy in patients treated with polydeoxyribonucleotide (PDRN) eye drops: a randomized, double-blind, placebo-controlled trial.

PURPOSE: The effect of polydeoxyribonucleotide (PDRN) eye drops vs placebo on corneal epithelial healing after photorefractive keratectomy (PRK) for correction of myopic and myopic-astigmatic defects was evaluated in a randomized, double-blind clinical trial. Primary endpoint for efficacy was the evolution of corneal re-epithelialization. Secondary endpoint was the evaluation of PDRN eye drops tolerability. METHODS: Sixty eyes were enrolled in the study, randomly allocated into standard therapy plus placebo eye drops (30 eyes), or standard therapy plus PDRN eye drops (30 eyes). Checks were carried out preoperatively and at days 1, 2, 3, and 7 of the follow-up. Six eyes dropped out (four in PDRN group, two in placebo group) for reasons unrelated to the study. RESULTS: On day 2, the disepithelialized area was 8.4 mm2+/-9.2 (mean+/-SD) in controls and 6.0 mm2+/-6.8 in PDRN group. On day 3 a complete corneal re-epithelialization was found in 20 out of 26 (77%) eyes of PDRN group and in 17 out of 28 (61%) eyes of placebo group (p<0.05 in percentage terms). On day 7 of follow-up, all eyes appeared to be completely re-epithelialized. The mean score of corneal evaluation on day 3 was 2.9 in PDRN group and 3.75 in control group (p<0.05 between groups). No adverse events occurred during the study. CONCLUSIONS: The data of the study have shown that after PRK, PDRN stimulates corneal epithelium regeneration. PDRN eye drops administration four times a day is well tolerated by patients during the re-epithelialization stage. A much larger clinical study should be performed in order to prove the results obtained in this pilot study.

Clinical evaluation of corneal epithelialization after photorefractive keratectomy in a patient treated with Polydeoxyribonucleotide (PDRN) eye drops: a randomized, double-blind, placebo-controlled trial.

PURPOSE: The effect of polydeoxyribonucleotide (PDRN) eye drops vs placebo on corneal epithelial healing after photorefractive keratectomy (PRK) for correction of myopic and myopic-astigmatic defects was evaluated in a randomized, double-blind clinical trial. Primary endpoint for efficacy was the evolution of corneal re-epithelialization. Secondary endpoint was the evaluation of PDRN eye drops tolerability. METHODS: Sixty eyes were enrolled in the study, randomly allocated into standard therapy plus placebo eye drops (30 eyes), or standard therapy plus PDRN eye drops (30 eyes). Checks were carried out preoperatively and at days 1, 2, 3, and 7 of the follow-up. Six eyes dropped out (four in PDRN group, two in placebo group) for reasons unrelated to the study. RESULTS: On day 2, the disepithelialized area was 8.4 mm2 9.2 (mean SD) in controls and 6.0 mm2 6.8 in PDRN group. On day 3 a complete corneal re-epithelialization was found in 20 out of 26 (77%) eyes of PDRN group and in 17 out of 28 (61%) eyes of placebo group (p<0.05 in percentage terms). On day 7 of follow-up, all eyes appeared to be completely re-epithelialized. The mean score of corneal evaluation on day 3 was 2.9 in PDRN group and 3.75 in control group (p<0.05 between groups). No adverse events occurred during the study. CONCLUSIONS: The data of the study have shown that after PRK, PDRN stimulates corneal epithelium regeneration. PDRN eye drops administration four times a day is well tolerated by patients during the re-epithelialization stage. A much larger clinical study should be performed in order to prove the results obtained in this pilot study.(Eur J Ophthalmol 2004; 14: 284-9).

Combined natural killer cell and dendritic cell functional deficiency in KARAP/DAP12 loss-of-function mutant mice.

KARAP/DAP12 is a transmembrane polypeptide with an intracytoplasmic immunoreceptor tyrosine-based activation motif (ITAM). KARAP/DAP12 is associated with several activating cell surface receptors in hematopoietic cells. Here, we report that knockin mice bearing a nonfunctional KARAP/DAP12 ITAM present altered innate immune responses. Although in these mice NK cells are present and their repertoire of inhibitory MHC class I receptors is intact, the NK cell spectrum of natural cytotoxicity toward tumor cell targets is restricted. KARAP/DAP12 loss-of-function mutant mice also exhibit a dramatic accumulation of dendritic cells in muco-cutaneous epithelia, associated with an impaired hapten-specific contact sensitivity. Thus, despite its homology with CD3zeta and FcRgamma, KARAP/DAP12 plays a specific role in innate immunity, emphasizing the nonredundancy of these ITAM-bearing polypeptides in hematopoietic cells.

Association of signal-regulatory proteins beta with KARAP/DAP-12.

The signal-regulatory proteins (SIRP) are Ig-like cell surface receptors detected in hematopoietic and non-hematopoietic cells. SIRP are classified as SIRPalpha molecules, containing a 110- to 113-amino acid long, or SIRPbeta molecules, with a 5-amino acid long intracytoplasmic domain. SIRPalpha molecules belong to inhibitory immunoreceptor tyrosine-based inhibition motif (ITIM)-bearing molecules. The majority of ITIM-bearing receptors are paired with activating isoforms, which share highly related extracytoplasmic domains but harbor a shorter cytoplasmic domain devoid of ITIM and contain a charged amino acid residue in their transmembrane domain. Activating receptors are associated with immunoreceptor tyrosine-based activation motif (ITAM)-bearing proteins, such as KARAP/DAP-12 and FcRgamma. In this report, we show that human SIRPbeta1 is included in an oligomeric complex with KARAP/DAP-12 in hematopoietic and non-hematopoietic transfectant cells as well as in human monocytes. The physical association between SIRPbeta1 and KARAP/DAP-12 results in the functional coupling of SIRPbeta1 engagement to the recruitment of the protein tyrosine kinase Syk and to serotonin release in RBL cell transfectants. Therefore our results show that SIRPbeta1 acts as an activating isoform of SIRPalpha molecules, confirming the co-existence of inhibitory ITIM-bearing molecules, recruiting SHP-1 and SHP-2 protein tyrosine phosphatases, and activating counterparts, whose engagement couples to protein tyrosine kinases via ITAM-bearing molecules.

Signaling pathways engaged by NK cell receptors: double concerto for activating receptors, inhibitory receptors and NK cells.

Despite the absence of antigen-specific receptors at their surface, NK cells can selectively eliminate virus-infected cells, tumor cells and allogenic cells. A dynamic and precisely coordinated balance between activating and inhibitory receptors governs NK cell activation programs. Multiple activating and inhibitory NK cell surface molecules have been described, a group of them acting as receptors for MHC class I molecules. In spite of their heterogeneity, activating NK cell receptors present remarkable structural and functional homologies with T cell- and B cell-antigen receptors. Inhibitory NK cell receptors operate at early stages of activating cascades by recruiting protein tyrosine phosphatases via intra- cytoplasmic motifs (ITIM), a strategy which is widely conserved in hematopoietic and non-hematopoietic cells.

Gene structure, expression pattern, and biological activity of mouse killer cell activating receptor-associated protein (KARAP)/DAP-12.

Natural killer cell and T cell subsets express at their cell surface a repertoire of receptors for MHC class I molecules, the natural killer cell receptors (NKRs). NKRs are characterized by the existence of inhibitory and activating isoforms, which are encoded by highly homologous but separate genes present in the same locus. Inhibitory isoforms express an intracytoplasmic immunoreceptor tyrosine-based inhibition motif, whereas activating isoforms lack any immunoreceptor tyrosine-based inhibition motif but harbor a charged amino acid residue in their transmembrane domain. We previously characterized KARAP (killer cell activating receptor-associated protein), a novel disulfide-linked tyrosine-phosphorylated dimer that selectively associates with the activating NKR isoforms. We report here the identification of the mouse KARAP gene, its localization on chromosome 7 and its genomic organization in five exons. Point mutation and transfection studies revealed that KARAP is a novel signaling transmembrane subunit whose transduction function depends on the integrity of an intracytoplasmic immunoreceptor tyrosine-based activation motif. In contrast to previous members of the immunoreceptor tyrosine-based activation motif polypeptide family, KARAP is ubiquitously expressed on hematopoietic and nonhematopoietic cells, suggesting its association with a broad range of activating receptors in a variety of tissues.

p40/LAIR-1 regulates the differentiation of peripheral blood precursors to dendritic cells induced by granulocyte-monocyte colony-stimulating factor.

p40/LAIR-1, a member of the immunoglobulin superfamily, is a surface molecule broadly distributed among leukocytes which has been shown to down-regulate T and NK cell activation. In this study, we show that p40/LAIR-1 is highly expressed in CD14+ peripheral blood mononuclear cells (PBMC). When cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) for 10-14 days, CD14+ cells acquired morphologic and phenotypic features (i.e. loss of CD14 and expression of CD80bright and CD86bright) typical of dendritic cells (DC) and lost the expression of p40/LAIR-1. Engagement of p40/LAIR-1 (but not of CD58) by specific monoclonal antibodies prevented CD14+ PBMC differentiation into DC; when cultured in the presence of GM- CSF upon p40/LAIR-1 cross-linking, the resulting cells were CD14+CD80(dull)CD86(dull) and displayed a macrophage-like morphology. We have recently demonstrated that peripheral blood CD14+ cells co-expressing the CD34 progenitor marker represent the circulating precursors of CD83+ DC. Herein we show that cross-linking of p40/LAIR-1 prevented the maturation of CD14+CD34+ cells into CD83+ DC. This effect appears to be consequent to the impairment of GM-CSF receptor-mediated activation signaling. Indeed, triggering of GM-CSF receptors in both CD14+ and CD14+CD34+ cells led to increases in the intracellular free calcium concentrations which were inhibited by p40/LAIR-1 engagement. Taken together, these data suggest a possible regulating role played by p40/LAIR-1 in the process of differentiation from peripheral blood precursors into DC induced by GM-CSF.

IL-12-induced up-regulation of NKRP1A expression in human NK cells and consequent NKRP1A-mediated down-regulation of NK cell activation.

IL-12, in contrast to IL-2, strongly up-regulated the expression of the NKRP1A lectin molecule on human NK cells. This effect appeared to be specific for NKRP1A as the expression of other functional NK cell surface molecules such as CD16 and different killer inhibitory receptors (KIR) including CD158a and CD158b, p70 and p140 were not affected by culture in IL-12. In addition, we found that polyclonal or clonal NK cell populations derived in the presence of IL-2 displayed an increased expression of NKRP1A after culture in IL-12. The IL-12-induced NKRP1A expression was time and dose dependent, reaching a maximum by 7 days of culture in the presence of 2 ng/ml IL-12 and it was inhibited by the addition of anti-IL-12 monoclonal antibody. The IL-12-dependent NKRP1A up-regulation was abrogated by the incubation of NK cells with actinomycin D, thus suggesting that IL-12 induces de novo transcription of NKRP1A mRNA. Functional analysis revealed that the engagement of the NKRP1A molecule in IL-12- but not in IL-2-cultured NK cells leads to a strong inhibition of the cytolytic activity induced by cross-linking of CD16 or p46, a recently described NK cell-specific triggering surface molecule. Our findings suggest that IL-12 up-regulates the expression of NKRP1A which, in turn, can regulate NK cell activation induced via different triggering pathways. This would imply that NKRP1A-mediated functions may be regulatd by the cytokine microenvironment that NK cells may encounter at inflammatory sites.

p40 molecule regulates NK cell activation mediated by NK receptors for HLA class I antigens and TCR-mediated triggering of T lymphocytes.

p40 was previously described as a regulatory molecule capable of inhibiting both the natural and the CD16-mediated cytotoxicity of NK cells. In this study, we analyze the effect of p40 molecule engagement on the NK cell triggering induced by activating HLA class I-specific NK receptors (NKR) or on TCR alpha beta-mediated T cell activation. CD3-CD16+ NK cell clones expressing activating NKR (either CD94 or p50) were analyzed in a redirected killing assay using P815 target cells and appropriate mAb. A strong target cell lysis was detected in the presence of anti-NKR or anti-CD16 mAb alone. Addition of anti-p40 mAb resulted in a strong inhibition of both anti-NKR or anti-CD16 mAb-induced cytolysis. mAb specific for either CD45 or lymphocyte function associated antigen-1 did not exert any inhibitory effect in the same experimental system. Free intracellular calcium ([Ca2+]i) increase induced by mAb cross-linking of activating CD94 or p50 was inhibited by simultaneous engagement of p40 molecules, but not of other NK surface molecules including CD44 and CD56. In addition, cross-linking of p40 molecules strongly inhibited the CD94-induced tumor necrosis factor-alpha and IFN-gamma production. Analysis of TCR alpha beta or gamma delta T cell clones revealed that the engagement of p40 molecules, using specific mAb, induced some degree of inhibition only on anti-V beta (but not anti-V delta or anti-CD3) mAb-induced cytotoxicity. On the other hand, the p40 molecule engagement prevented T cell proliferation induced by either anti-V beta 8 or anti-V delta 2 mAb. A similar inhibitory effect was found on the IL-2-induced NK cell proliferation. Taken together, our present findings suggest that p40 may play a role in the regulation of NK and T lymphocyte activation and proliferation.

Expression of human NKRP1A by CD34+ immature thymocytes: NKRP1A-mediated regulation of proliferation and cytolytic activity.

In this study, we show that NKRP1A is expressed and functions on a subset of immature human thymocytes. We took advantage of the monoclonal antibody (mAb) 191B8 that was obtained by immunizing mice with cultured human thymocytes characterized by an immature surface phenotype [CD2- CD3- CD4- CD8- stem cell factor receptor (SCFR)+] and expressing cytoplasmic CD3 epsilon chain. The 191B8 antibody homogeneously reacted with the immunizing population but not with most unfractionated thymocytes. It stained a minor population of resting immature thymocytes co-expressing CD34, SCFR, or both. Following culture of the CD34+ or CD34- fractions of CD2- CD3- CD4- CD8- purified immature thymocytes with recombinant interleukin-2 (rIL-2), the 191B8-defined antigen was expressed on virtually all cells even when 191B8+ cells were removed from the starting population. On the other hand, no 191B8+ cells were detected in fresh or cultured thymocytes expressing a more mature phenotype. Biochemical analysis of 191B8 mAb-reactive molecules revealed, under non-reducing conditions, two bands displaying apparent molecular masses of 80 and 44 kDa and a single band of 44 kDa under reducing conditions. Digestion with proteases indicated that the 80-kDa form represented a homodimeric form of two 44-kDa molecules, while deglycosylation with N-glycanase suggested the existence of four N-glycosylation sites. Transfection of COS7 or NIH3T3 cells with hNKRP1A cDNA showed that the 191B8 mAb recognized NKRP1A as shown by both immunofluorescence analysis and immunoprecipitation experiments. Functional studies showed that the 191B8/NKRP1A molecule mediated strong inhibition of the cytolytic activity of cultured CD2- CD3- immature thymocytes against a panel of tumor target cells. More importantly, 191B8 mAb induced proliferation of CD2- CD3- fresh thymocytes which was not increased by rIL-2. Thus, we propose that NKRP1A molecules, which are expressed in highly immature thymocytes, may play a regulatory role in their growth and function.

Dissection of lymphocyte function-associated antigen 1-dependent adhesion and signal transduction in human natural killer cells shown by the use of cholera or pertussis toxin.

The effect of the guanosine triphosphate-binding protein (G-protein) inhibitors cholera toxin (Ctx) and pertussis toxin (Ptx) has been analyzed on lymphocyte function-associated antigen 1 (LFA-1)-dependent adhesion and signal transduction in human natural killer (NK) cells. Ctx, but not Ptx, inhibited the LFA-1-dependent adhesion of NK cells to tumor target cells which constitutively express the intercellular cell adhesion molecule-1 (ICAM-1) and to NIH/3T3 mouse fibroblasts stably transfected with human ICAM-1. This effect was detectable only by the use of the entire Ctx but not of the Ctx B subunit. In addition, Ctx could inhibit both NK cell binding and spreading to purified ICAM-1 protein. NK cell treatment with Ctx modified neither the surface expression of LFA-1 nor its Mg2+ binding site. These findings, together with the absence of any detectable effect of Ctx on the constitutive phosphorylation of LFA-1 alpha, suggests that this toxin modifies the avidity of LFA-1 for ICAM-1 by acting on LFA-1-cytoskeletal protein association. Unlike Ctx, Ptx did not affect NK cell adhesion. The effects of Ctx and Ptx are unlikely to depend on intracellular levels of cyclic adenosine 3',5'-monophosphate (cAMP), since a strong increase of cAMP was induced by both toxins. Moreover, this was confirmed by the observation that the LFA-1-dependent adhesion was not inhibited by the adenylate cyclase activator forskolin (FSK), the phosphodiesterase inhibitor isobutyl-1-methylxanthine (IBMX), or both, which increase intracellular cAMP levels. Unlike the differential effect on cell adhesion, both the intracellular calcium [Ca2+]i increase and phosphoinositide breakdown mediated via LFA-1 were consistently inhibited in a dose-dependent manner by both Ctx and Ptx. Also in this case, the inhibitory effect did not depend on an increase of intracellular cAMP as indicated by NK cell treatment with FSK, IBMX, or both. Further evidence of the involvement of G-proteins in LFA-1-mediated signal transduction was the inhibitory effect of the GDP analog guanosine-5'-O-2-thiodiphosphate (GDP beta S) on LFA-1-mediated calcium mobilization. Taken together, our data provide evidence that the LFA-1-mediated NK cell adhesion and signal transduction are partially independent phenomena which may be regulated by different G-proteins.