Induction of cytokines and expression of surface receptors in Mono Mac 6 cells after infection with different Legionella species

The ability of Legionella species to multiply within human mononuclear phagocytes is usually regarded as being associated with their pathogenicity. Activation of host cells results in inhibition of intracellular Legionella multiplication. The most effective substance to induce macrophage activation, both in vivo and in vitro, is interferon-gamma. In addition, some evidence exists that macrophage-derived cytokines may contribute to the host defense against L. pneumophila, but the production of pro- and antiinflammatory cytokines by monocytes after infection with different Legionella species has not been reported with regard to their ability to multiply within the host cells. We therefore examined the production of TNF-alpha, IL-1, IL-6, IL-8, IL-10 and TGF-beta by Mono Mac 6 cells after infection with Legionella species of different human prevalence that differ in their ability to replicate within this macrophage-like cell line. After infection, Mono Mac 6 cells showed a cytokine response with time kinetics characteristic for the cytokine. Maximum cytokine levels produced differed with Legionella species, but were not related to intracellular multiplication rates. Moreover, LPS-tolerant Mono Mac 6 cells, which failed to produce cytokines, showed intracellular increase or decrease of bacterial numbers identical to that of untreated Mono Mac 6 cells. By FACS analysis, an up-regulation of CD14 (LPS receptor) and CD54 (ICAM-1) could be demonstrated. We conclude that, in the Mono Mac 6 cell line, induction of macrophage-derived cytokines after infection with members of the genus Legionella mimics an inflammatory reaction without association with intracellular multiplication rate.

Nongenomic effects of androstenedione on human granulosa luteinizing cells

This study examines rapid (5-60 s) effects of androgens on the cytosolic free Ca2+ concentration ([Ca2+]i) in human granulosa lutenizing cells. Cells were obtained from human preovulatory follicles, and [Ca2+]i was measured with the use of the Ca(2+)-responsive fluorescent dye fluo-3. Molar concentrations between 100 pmol/L and 1 mumol/L androstenedione increased [Ca2+]i within 5 s after addition to cells. This [Ca2+]i increase resulted from both Ca2+ influx, as shown by the effects of ethyleneglycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and the voltage-dependent Ca2+ channel blocker verapamil, and Ca2+ mobilization from the endoplasmic reticulum, as shown by the effects of thapsigargin. Treatment with pertussis toxin and U-73,122, a specific inhibitor of phospholipase C, abolished the effects of androstenedione on [Ca2+]i. Flutamide, a nuclear androgen receptor antagonist, did not block the increase in [Ca2+]i induced by androstenedione. Testosterone (100 pmol/L to 1 mumol/L) had no effect. This is the first report showing that androstenedione increases [Ca2+]i in granulosa cells. These data provide evidence for the presence in granulosa cells of a novel, short term mechanism of androstenedione action involving voltage-dependent Ca2+ channels in the plasma membrane and phospholipase C activation via a pertussis toxin-sensitive G protein.

Functional role of endogenous CD14 in lipopolysaccharide-stimulated bone resorption

Lipopolysaccharide (LPS) is a bacterial cell component that plays multifunctional roles in inflammatory reactions, and one of these roles is that of a powerful stimulator of bone resorption. However, the mechanism by which LPS stimulates bone resorption is not yet understood. In the present study, we show, by using mouse embryonic calvarial cells, that endogenous CD14 and interleukin-1 beta (IL-1 beta) play an important role in the LPS-mediated bone resorption and that interferon-gamma (IFN-gamma) functions as a strong inhibitor of this resorption by suppressing LPS-stimulated expression of CD14 and IL-1 beta genes in the calvarial cells. We observed that LPS-stimulated differentiation of osteoclastic cells and bone resorption were markedly neutralized by anti-mouse CD14 antibody and were clearly inhibited by anti-sense CD14 oligonucleotide treatment. In addition, because LPS stimulated CD14 gene expression in the calvarial cells, these observations demonstrate the precise role of endogenous CD14 in LPS-stimulated differentiation of osteoclastic cells and bone resorption. However, the stimulation of the differentiation of osteoclastic cells and bone resorption was also inhibited by anti-mouse IL-1 beta antibody. Interestingly, anti-sense CD14 oligonucleotide inhibited LPS-stimulated expression of the IL-1 beta gene in the calvarial cells. These observations suggest a functional role of endogenous CD14 in LPS-stimulated expression of the IL-1 beta gene in the cells. Because IFN-gamma is a potent inhibitor of bone resorption stimulated by IL-1, in additional experiments, we examined whether IFN-gamma is able to inhibit LPS-stimulated differentiation of osteoclastic cells and bone resorption. We found that IFN-gamma inhibited these stimulations by suppressing CD14 and IL-1 beta genes in the calvarial cells. The present study thus clearly demonstrates a functional role of endogenous CD14 in LPS-stimulated bone resorption.

Expression and function of NKRP1A molecule on human monocytes and dendritic cells

In this study, we analyzed the expression and function of the lymphocyte surface lectin NKRP1A on peripheral blood monocytes (Mo) or Mo and dendritic cells (DC) derived from thymic and bone marrow precursors. De novo expression of NKRP1A and CD14 molecules was detected upon culture of CD2- CD3- CD14- CD16- CD1a- NKRP1A- immature thymic precursors for 7 days in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Under these culture conditions, by day 21, a fraction of cells had lost CD14 and acquired both CD80 (B7.1) and CD86 (B7.2) molecules. These cells displayed a DC-like morphology and were surface NKRP1A positive. CD34+ NKRP1A- CD14- precursors, isolated from bone marrow and cultured in the presence of GM-CSF, also expressed both NKRP1A and CD14: these antigens were newly expressed on about one third of cells which had lost the CD34 precursor marker. In addition, NKRP1A was constitutively present on resting CD14+ peripheral blood Mo. When these cells were cultured in the presence of GM-CSF, the resulting DC population retained the expression of NKRP1A and acquired CD80, while they lost the CD14 antigen. Functional analysis revealed that the engagement of NKRP1A molecule leads to a strong intracellular calcium ([Ca2+]i) increase both in resting peripheral blood Mo and in vitro-derived DC. [Ca2+]i increase was mainly due to extracellular calcium influx, as it was completely abrogated by the addition of EGTA. More importantly, the engagement of the NKRP1A molecule induced interleukin (IL)-1 beta and IL-12 production by resting Mo and DC, respectively. Altogether these data indicate that NKRP1A lectin is present at the surface of Mo and DC and may play a relevant role in the activation and function of both cell types.

[LPS receptor expression and lps binding capacity of monocytes and macrophages in swine]

The expression of the lipopolysaccharide (LPS) receptor CD14, being of importance for an effective immune response, and the direct measurable binding of LPS molecules by alveolar macrophages (AM), peritoneal macrophages (PM) and peripheral blood mononuclear cells (PBMC) of swine were determined. Additionally, the influence of an experimental intrabronchial infection with Pasteurella multocida on these parameters was investigated. Whereas the AM and the PM differed only negligibly regarding their share of CD14 bearing and LPS binding cells, in contrast to AM the intensity of the LPS-binding of PM was significantly higher. Among the PBMC, two populations could be detected which expressed the CD14 with different intensity, whereas the LPS-binding of both populations was similarly pronounced. Following infection of the animals, AM showed an unchanged percentage of CD14 positive cells and simultaneously an increased CD14 receptor expression. On the other hand, the percentage of the LPS-binding cells rose, while no changes of the intensity of LPS-binding were observable. The studies revealed that intrabronchial infection results in local and systemic alterations of CD14 expression and LPS-binding capacity of different cell populations. However, a direct correlation between the appearance of CD14- and LPS-binding does not seem to inevitably exist, indicating probably CD14-independent LPS-binding.

Effect of oxidized low density lipoprotein on thrombomodulin expression by THP-1 cells

We have investigated the effects of oxidized low density lipoproteins (oxidized LDL) on the expression of TM by THP-1 monocytic cells. TM antigen levels and its cofactor activity for thrombin-dependent protein C activation were increased by oxidized LDL and accompanied by an increase in TM mRNA levels. Incubation of THP-1 cells with 300 microg/ml oxidized LDL for 24 h resulted in an 80% increase of cellular TM antigen levels. Native LDL and acetylated LDL did not affect the TM expression by these cells. The resultant aqueous phase after extraction of oxidized LDL by chloroform/methanol increased the TM antigen levels as well as oxidized LDL. Phorbol 12-myristate 13-acetate (PMA) also increased the TM antigen level 2.1 times the control and was accompanied by the adhesion of cells to plastic dishes and increasing macrophage cell surface antigen CD14 levels. In contrast, oxidized LDL did not induce differentiation to the macrophage. The present results indicate that oxidized LDL increases cellular TM antigen without cellular differentiation and that up-regulation of TM by oxidized LDL in monocytes may have some implication in atherosclerosis.

Regulation of human monocyte apoptosis by the CD14 molecule

Bacterial products such as LPS have been shown to activate monocytes and to increase CD14 expression, while anti-inflammatory cytokines, i.e., IL-4, down-regulate CD14. Furthermore, activation of monocytes increases survival, whereas deactivation evokes apoptosis (programmed cell death, PCD). This correlation among activation, CD14 expression, and the lifespan of the cells prompted us to investigate the role of CD14 in monocyte apoptosis. The effects of LPS and IL-4 on the expression of CD14, indicated by binding of Leu M3 Ab, and PCD of monocytes were studied simultaneously and in a kinetic fashion by multiparameter flow cytometry. Monocyte PCD was determined by binding of FITC-conjugated annexin V, which indicates apoptotic cell death in early stages, and was confirmed using well-established detection methods, i.e., DNA electrophoresis, electron microscopy, or colorimetric DNA staining. The present study shows that the LPS-induced increase in CD14 expression rescued monocytes from apoptosis, whereas IL-4 treatment first down-regulated CD14 expression and consecutively evoked apoptosis. CD14-/annexin V- monocytes were not apoptotic as confirmed by DNA electrophoresis, whereas CD14-/ annexin V+ monocytes showed clear apoptotic features. Kinetic studies ruled out that monocytes first bound annexin V and later lost the CD14 Ag. Other molecules, such as HLA-A, -B, and -C Ags, were not down-regulated during apoptosis. Enzymatic removal of membrane-bound CD14 by phosphatidylinositol-specific phospholipase C evoked PCD similarly to IL-4. These results suggest that regulation of CD14 receptor expression is an early effector mechanism mediating life or death of monocytes. Down-regulation or removal of the receptor triggers apoptosis, whereas up-regulation promotes survival.

Lipopolysaccharide activates the muscularis macrophage network and suppresses circular smooth muscle activity

Bacterial lipopolysaccharide (LPS) is a causative agent of sepsis-induced ileus. Although it is known that LPS activates macrophages and initiates inflammation, the consequences of LPS on the macrophage network and a potential inflammatory response within the intestinal muscularis have not been investigated. This study was designed to identify cellular and functional changes in rat intestinal muscularis after intraperitoneal LPS. Histo- and immunohistochemistry were used to phenotype leukocytes. Functional alterations were determined using an organ bath. Compared with controls, LPS caused a 21-fold increase in staining for the lymphocyte activation marker-1 (LFA-1) localized to the ED2+ macrophage network 1 h after injection. This was followed by a significant infiltration of neutrophils, mast cells, and monocytes into the muscularis. LPS also caused a 62% reduction in spontaneous circular muscle activity and a 91% suppression of bethanechol-stimulated contractions 12 h after injection. These results demonstrate that endotoxemia 1) acutely activates the muscularis macrophage network, 2) causes the extravasation of leukocytes, and 3) results in circular muscle impairment.

Long-term exposure of HL60 cells to 1,25-dihydroxyvitamin D3 reduces their tumorigenicity: a model for cancer chemoprevention

Several lines of evidence suggest that 1,25-dihydroxyvitamin D3 (1,25D3) may be important in chemoprevention of human cancer. Here, we show that human promyelocytic leukemia cells HL60 cultured in the presence of 30 nM 1,25D3 (30A cells) for 3 years exhibited a reduced rate of tumor growth when injected into nu/nu mice, while cells grown in 40 nM 1,25D3 (40AF cells) failed to form detectable tumors in 11 out of the 12 inoculated mice, interestingly, both 30A and 40AF cells grew approximately twice as fast as the parental HL60-G cells under tissue culture conditions, even in the presence of 1,25D3, to which they developed resistance. Tests of the susceptibility of these cells to natural killer (NK) cell cytotoxicity showed that 40AF, but not HL60-G or 30A cells, were targets for the murine spleen NK cells. However, lysis of 30A cells was also detected when human NK cells were used in this assay, though the effector-to-target cell ratio necessary to obtain significant lysis above background levels was higher for 30A (80:1) than for 40AF (10:1) cells. These results suggest a mechanism for the reported chemopreventive effects of sunlight-generated 1,25D3 or dietary vitamin D3.

Molecular cloning of bovine CD14 gene

Genomic DNA encoding bovine CD14 was isolated from a bovine (Holstein) genomic library. Utilizing PCR fragment of mouse CD14 gene as a probe, we screened 9 x 10(5) plaques and obtained 3 clones containing the bovine CD14 gene. DNA sequencing showed that bovine CD14 gene encodes 373 amino acids, and the coding sequence was separated by a 90 nt intron. The identity of the deduced amino acid sequence of bovine CD14 was 61-73% to those of mouse, rabbit and human. Northern blot analysis revealed that CD14 mRNA (1.5 kb) was expressed in the lung. Expression of CD14 mRNA was stimulated about 2-fold in bovine peripheral blood macrophage activated with LPS in vitro.

Involvement of diacylglycerol production in activation of nuclear factor kappaB by a CD14-mediated lipopolysaccharide stimulus

Exposure of Chinese hamster CHO-K1 transfectant cells expressing mouse CD14 (CHO/CD14 cells) to lipopolysaccharide (LPS) induced rapid elevation of the cellular diacylglycerol (DAG) and choline/phosphocholine levels and nuclear translocation of nuclear factor kappaB (NFkappaB). When cells were incubated with short-chain DAG analogues or bacterial phospholipase C, NFkappaB activation occurred even without the LPS stimulus. Treatment of CHO/CD14 cells with tricyclo[5.2.1.0(2.6)]decyl-(9[8])xanthogenate (D609), an inhibitor of phosphatidylcholine-specific phospholipase C and phospholipase D, almost completely inhibited not only the LPS-dependent production of DAG and choline/phosphocholine but also the LPS-dependent NFkappaB activation. In contrast, treatment of cells with 1-(6-{[3-methoxyoestra-1,3, 5(10)-trien-17beta-yl]-1H-pyrrole-2,5-dione (U73122), an inhibitor of phosphatidylinositol-specific phospholipase C in vitro, did not affect the LPS-dependent activation of NFkappaB. Production of DAG and activation of NFkappaB after the LPS stimulus were observed in mouse macrophage-like J774.1 cells, and this response to LPS by J774. 1 cells was also inhibited by D609. These results suggest that the production of DAG from phosphatidylcholine was upstream of NFkappaB activation in response to a CD14-mediated LPS stimulus.

Effect of SP-A and surfactant lipids on expression of cell surface markers in the THP-1 monocytic cell line

Pulmonary surfactant and its lipid components inhibit cell proliferation and cytokine expression. Surfactant protein A (SP-A) can stimulate these same functions. We assessed the impact of SP-A and surfactant lipids on the expression of the cell surface markers, CD14, CD54 (intercellular adhesion molecule-1), and CD11b, by the human monocytic cell line THP-1 using fluorescent antibody staining and fluorescence-activated cell sorting. Under basal conditions CD14 and CD54 were undetectable, and CD11b was expressed at low levels. Incubation of the cells in 1,25(OH)2D3 alone, or with low doses of surfactant lipids, increased CD14, CD54, and CD11b. Expression was increased further by SP-A. However, the SP-A-induced increases in cell markers were blocked by simultaneous treatment with lipid. The results suggest that the ability of the macrophage to participate in an inflammatory response is enhanced by SP-A alone or by surfactant containing a higher than normal proportion of SP-A. They further suggest that the addition of lipids results in a phenotype less prone to initiate an inflammatory reaction.

Phenotypic changes of monocytes induced by HIV-1 gp120 molecule and its fragments

Several phenotypic and functional changes of monocytes (M phi) have been described in HIV-1+ subjects and AIDS patients. Some of these changes that are pertinent for immunopathogenesis of the disease may be induced by HIV-1 envelope glycoprotein 120 (gp120). In the present study the effect of recombinant full length gp120 (FLgp120) and its two fragments: rp120cd (aa 410-511) and rp120 (aa 446-511) on the expression of the surface molecules of M phi cultured in vitro was determined. The FLgp120 and rp120cd caused upregulation of CD14 and CD44. The rp120cd peptide significantly increased the expression of CD16 (Fc gamma receptor type III) and TNF receptor type II. In contrast, the rp120 downregulated HLA-DR, CD64 (Fc gamma RI), interferon gamma receptor and induced IL-10 production by M phi. This study indicates that gp120 molecule and its fragments may induce several phenotypic changes of M phi in particular the increased proportion of CD14+CD16+ cells that is observed in the blood of AIDS patients. These results provide further evidence for variable response of M phi to gp120 which may explain the variability of phenotypic changes and heterogeneity of M phi subsets seen in HIV-1 disease.

CHO transfectants produce large amounts of recombinant protein in suspension culture

Chinese hamster ovary (CHO) cells transfected with various genes are widely used as adherent cell monolayers to produce recombinant proteins. In this report we present a new culture technique for CHO cells transfected with the vector pPOL-DHFR-CD14 using a minifermenter (miniPERM, Heraeus) for the production of recombinant human endotoxin receptor CD14 (rCD14). The transfectants were cultured for 12-17 days under serum-free conditions and formed spheroids. From this system we harvested supernatants containing up to 3.1 mg/ml recombinant CD14 (rCD14). This represents a 200-fold increase of rCD14 yield compared to conventional adherent CHO cell culture.

Uncoupling of cell cycle arrest from the expression of monocytic differentiation markers in HL60 cell variants

Differentiation generally leads to cell cycle arrest. Human leukemia HL60 cells respond to the presence of 1,25-dihydroxyvitamin D3 (1,25D3) by expressing a number of markers of the monocyte/macrophage phenotype and become arrested predominantly in the G1 phase of the cell cycle. We have recently reported a series (A) of 1,25D3-resistant variants of HL60 cells which proliferate in the presence of 1,25D3 and do not express differentiation markers (Exp. Cell Res. 224, 312, 1996). We now describe another series (B) of such variants, which differ from A series cells grown in similar concentrations of 1,25D3 in that they express the CD14 antigen and nonspecific esterase, characteristic of the monocyte, while continuing to proliferate and they develop hypotetraploid DNA (4C) content at higher concentrations of ambient 1,25D3 than the A series cells. Cells in the B series with 4C DNA content (100B and 200B) also differed from the A series 4C cells by the absence of DNA binding by the full-length Sp1 transcription factor. However, B series cells resembled the A series cells in exhibiting faster growth rates than the parental HL60 cells and showed high levels of vitamin D receptor and retinoid receptor X proteins. These results show that the initial steps in the 1,25D3 signaling pathway are intact in B series resistant cells and lead to the appearance of early markers of monocytic differentiation. However, the progression to subsequent events which comprise terminal differentiation and cell cycle arrest is halted during the adaptation to the presence of 1,25D3 in these cells. Thus, the availability of these variant cells should provide a system for studying the link between differentiation and cell cycle arrest.

Multinucleated cells in pigmented villonodular synovitis and giant cell tumor of tendon sheath express features of osteoclasts

Pigmented villonodular synovitis (PVNS) and the histologically related lesion giant cell tumor of tendon sheath (GCTTS) are idiopathic, proliferative lesions that can induce osteolysis and formation of bone cysts. These lesions contain two predominant cell types: mononuclear polyhedral cells and multinucleated cells (MNCs). Previous studies demonstrated that the mononuclear cells exhibit phenotypic features consistent with derivation from a monocyte/macrophage lineage. The cell lineage of the MNCs and their relationship to osteoclasts are not known. To characterize the MNCs in these lesions and to establish the relationship of these MNCs to osteoclasts, histological sections from six cases of PVNS and two cases of GCTTS were studied. Mononuclear cells expressed CD14 and HLA-DR, in keeping with their relationship to cells of the monocyte/macrophage lineage. Characterization of the MNCs revealed features associated with an osteoclast phenotype. Seven of the eight specimens contained MNCs that were intensely tartrate-resistant acid phosphatase positive; approximately 5% of the mononuclear cells were tartrate-resistant acid phosphatase positive, and these tended to surround MNCs. MNCs in both lesions reacted strongly with the 23C6 monoclonal antibody that recognizes the alpha V beta 3 integrin (the vitronectin receptor), as did several mononuclear cells surrounding the MNCs. Most MNCs did not express CD14 or HLA-DR. Expression of receptors for calcitonin, a marker for osteoclasts, was detected on MNCs after incubation of sections with 125I-labeled salmon calcitonin and emulsion autoradiography. MNCs in four of six PVNS and two of two GCTTS samples demonstrated specific calcitonin binding. Expression of mRNA for calcitonin receptor was confirmed in all cases by reverse transcriptase polymerase chain reaction. These results demonstrate that MNCs in PVNS and GCTTS express phenotypic features of authentic osteoclasts and suggest that osteoclast-like multinucleated cells can arise in synovial soft tissues remote from bone.

[Increased sensitivity to endotoxin and its molecular mechanism after hemorrhagic shock]

OBJECTIVE

To study the increasing sensitivity to endotoxin induced by hemorrhagic shock and its mechanism.

METHODS

Routine biochemical assay, reverse transcription-polymerase chain reaction. (RT-PCR) and cell in situ hybridization were used to investigate the effects of low-level endotoxin under hemorrhagic shock and its possible mechanism.

RESULTS

In rabbits, blood pressure levels were significantly decreased, and plasma lactate and beta-glucuronidase (beta-G) levels increased in hemorrhagic shock (HS) + LPS group, all of which were significantly different from those in the LPS or HS group. All of the animals in the HS + LPS group were dead while those in the LPS or HS group survived 24 hours after shock. The results of RT-PCR showed that expression of lipopolysaccharide-binding protein (LBP) mRNA in the liver, lungs and kidneys was increased in rats after shock and resuscitation. The expression of CD144 mRNA in the peritoneal macrophages in mice was also enhanced after hemorrhagic shock and subsequent resuscitation showed by cell in situ hybridization.

CONCLUSION

Hemorrhagic shock can significantly increase the sensitivity to endotoxin possibly because of up-regulation of LBP/CD14 after shock.

C-C chemokines released by lipopolysaccharide (LPS)-stimulated human macrophages suppress HIV-1 infection in both macrophages and T cells

Human immunodeficiency virus-1 (HIV-1) expression in monocyte-derived macrophages (MDM) infected in vitro is known to be inhibited by lipopolysaccharide (LPS). However, the mechanisms are incompletely understood. We show here that HIV-1 suppression is mediated by soluble factors released by MDM stimulated with physiologically significant concentrations of LPS. LPS-conditioned supernatants from MDM inhibited HIV-1 replication in both MDM and T cells. Depletion of C-C chemokines (RANTES, MIP-1 alpha, and MIP-1 beta) neutralized the ability of LPS-conditioned supernatants to inhibit HIV-1 replication in MDM. A combination of recombinant C-C chemokines blocked HIV-1 infection as effectively as LPS. Here, we report an inhibitory effect of C-C chemokines on HIV replication in primary macrophages. Our results raise the possibility that monocytes may play a dual role in HIV infection: while representing a reservoir for the virus, they may contribute to the containment of the infection by releasing factors that suppress HIV replication not only in monocytes but also in T lymphocytes.

Enhanced expression of CD14 antigen on myeloid lineage cells derived from the bone marrow of patients with severe rheumatoid arthritis

OBJECTIVE

We previously reported the accumulation of abnormal myeloid cell populations reacting with CD14 (MY4) monoclonal antibody in the iliac and epiphyseal bone marrow of patients with severe rheumatoid arthritis (RA). Therefore, we investigated in vitro production and modulation of CD14+ myeloid cells from iliac bone marrow cells.

METHODS

Mononuclear cells were prepared from iliac bone marrow aspirates from patients with RA. The presence of unusual myeloid cells was assessed by 2 color flow cytometry of cells cultured under various conditions.

RESULTS

Cultured iliac bone marrow cells of patients with severe RA produced 14.7% of CD14+ CD15+ cells on average. Cultures derived from healthy donors and from patients with a milder form of RA produced fewer CD14+ CD15+ cells (< 10%). The production of CD14+ CD15+ cells was enhanced by granulocyte macrophage colony stimulating factor and interleukin 1beta, but inhibited by T lymphocytes.

CONCLUSION

Production and modulation of CD14+ myeloid cells were observed in iliac bone marrow of patients with severe RA.

Monocyte-macrophage differentiation induced by coculture of retinal pigment epithelium cells with monocytes

Macrophages play an important role in proliferative vitreoretinopathy (PVR). Since macrophage maturation may be modulated by the local microenvironment, we determined the effect of retinal pigment epithelium (RPE) cells interacting with monocytes on macrophage maturation. The enriched monocyte fraction of peripheral blood mononuclear cells was cocultured with RPE cells. Cell-free supernatants conditioned during the culture periods 0-4 days (growing RPE cells) and 4-8 days (confluent RPE cells) were tested for their capacity to induce monocyte/macrophage differentiation of the promyelocytic cell line HL-60, which was measured by the expression of CD11c and CD14 and flow cytometry. RPE cells released factors that increased the CD14 expression on HL-60 cells in terms of percentage of positive cells (22.7% vs. control 10.4%). RPE-cell-conditioned supernatants had no effect on the CD11c expression. Monocytes secreted substances that increased the expression of CD11c (20.5% vs. control 9.1%; p = 0.003) and CD14 (31.6% vs. control 10.4%; p < 0.0001). Supernatants from cocultures increased the CD11c (19.8%) and CD14 expression (40.8%) to values that were similar to the sum of those of cell monocultures. Supernatants conditioned during the later culture had no effect on CD14 and CD11c expression. We conclude that invading monocytes and RPE cells could create an intraocular microenvironment that supports macrophage maturation during the initial stage of PVR.

Growth of Chlamydia pneumoniae induces cytokine production and expression of CD14 in a human monocytic cell line

Chlamydia pneumoniae was able to survive and to multiply in the human monocytic cell line Mono Mac 6. Growth of C. pneumoniae induced production of tumor necrosis factor alpha, interleukin 1beta, and interleukin 6, as well as up-regulation of the CD14 molecule in a time-dependent manner. Infection of monocytic cells and a proinflammatory cytokine response may be important in C. pneumoniae pathogenesis.

Induction of CD14 expression in Lpsn, Lpsd and tumor necrosis factor receptor-deficient mice

The involvement of CD14 in lipopolysaccharide (LPS) recognition and signaling has been demonstrated in several studies. For this reason, we investigated whether the resistance of Lpsd mice to LPS might be related to an impaired CD14 expression. We compared the in vivo and in vitro expression of CD14 in Lpsn (LPS sensitive) and Lpsd mice, and its modulation by LPS, killed gram-negative and gram-positive bacteria and double-stranded (ds)RNA. Untreated Lpsn and Lpsd cultured macrophages (M phi), expressed similar amounts of CD14 mRNA and membrane-bound (m)CD14. LPS enhanced CD14 expression only in Lpsn M phi, while all bacteria, or dsRNA, enhanced CD14 in Lpsn and Lpsd M phi. Similarly, in vivo administration of LPS induced or enhanced CD14 mRNA in different organs of Lpsn mice only, while bacteria or dsRNA in both types of mouse. Furthermore, exogenous recombinant tumor necrosis factor (TNF) induced in vivo and in vitro enhanced CD14 expression in Lpsn, Lpsd and also in TNF receptor 2-deficient (TNFR2-/-) mice, but failed to do so in TNFR1-/- mice, showing that TNFR1 mediates the effect of TNF on CD14. However, LPS, bacteria and dsRNA induced CD14 in both TNFR2-/- and TNFR1-/- mice to a similar extent, revealing that this induction does not require TNF signaling.

Detection of CD 14 on migrated monocytes by specific antibody: a possible quantification for blood monocyte chemotaxis

In the present study we investigated the possibility to use antigen-antibody recognition for detection of monocyte chemotaxis in the 48-well microchamber assay. The described method is based on recognition of cell-specific antigenic determinants present on the migrated monocytes. After conventional 48-well chemotaxis, the migrated cells were incubated with an antibody against the monocyte surface marker CD14 (3C10 hybridoma). Subsequent incubation with enzyme-coupled antibodies and their substrate allowed the antigen and hence the migrated cells carrying this antigen, to be detected and measured in a microplate reader. Our results show that chemotaxis of normal blood monocytes towards the monocyte chemoattractants FMLP and MCP-1 could be detected with the anti-CD14 antibody 3C10 in combination with a horse-radish peroxidase coupled antibody, and that the optical density is a measure for cell number per well (positive correlation, r = 0.95). Incubation of monocytes with the applied chemoattractants FMLP and MCP-1 did not change the CD14 expression as was determined by FACScan analysis. Therefore we conclude that it is possible to use antibodies directed against antigenic determinants like CD14 to detect blood monocyte migration in a more objective way compared to subjective counting of cells on a filter. Eventually, this method can be valuable, especially for chemokine research since chemokines exert their effects on specific target cell populations. By varying the detection antibody, other cell populations besides monocytes may be quantified.

Regulation of CD14 expression on human adult central nervous system-derived microglia

Microglial cells function as regulators of immune reactivity within the CNS and may contribute to tissue injury under inflammatory conditions. Such functions are correlated with their state of activation. In this study, we report the de novo expression of CD14 by adult human CNS-derived microglia which acquire a bipolar activated morphologic phenotype in dissociated tissue culture. Surface CD14 expression can be down-regulated by interaction with its ligand lipopolysaccharide (LPS), and by the T-helper (Th1) cytokine interferon-gamma (IFN-gamma) or the Th2 cytokine interleukin-4 (IL-4). Semiquantitative polymerase chain reaction (PCR) analysis of CD14 mRNA expression under each condition suggests a different mechanism accounting for the reduced surface expression. LPS down-regulates CD14 mRNA, consistent with a feed-back signal preventing over-stimulation. IFN-gamma augments CD14 transcription, suggesting cleavage of surface CD14 consequent to general cell activation. IL-4 decreases mRNA production likely reflecting a generalized suppressive effect. The effect of LPS, IFN-gamma and IL-4 on CD14 expression differes from their effect on expression of the immune-accessory molecules B7-1 and HLA-DR, and on production of tumor necrosis factor-alpha (TNF-alpha), whose secretory pathway is similar to that of CD14. These results indicate the selective effects of molecules, likely to be present in the infected or inflamed CNS, on regulating CD14 expression and that there can be differential regulation of immune response relevant molecules expressed by activated microglia.

Effects of macrophage colony-stimulating factor (M-CSF) on lipopolysaccharide (LPS)-induced mediator production from monocytes in vitro

M-CSF is a macrophage-lineage-specific growth factor that causes proliferation and differentiation of progenitor cells in the bone marrow. To investigate the effects of M-CSF on more matured cells, human monocytes were cultured in the presence or absence of M-CSF for 6 days. Addition of M-CSF at more than 10(2) U/ml resulted in higher viability and caused morphological differentiation to large macrophage-like cells. LPS-induced mediator production was also compared between M-CSF-treated and control cell. Monocytes were incubated with or without M-CSF for 3 days, and were stimulated with 1 microgram/ml of LPS for 2 days. IL-1 beta was not detected in the both culture supernatants, and PGE2 production was not influenced by M-CSF. However, amounts of G-CSF, GM-CSF, IL-6, and TNF-alpha produced in response to 1 microgram/ml of LPS were 1.5 to 2 times greater from monocytes treated with 10(4) U/ml of M-CSF than from control cells. The priming effect of M-CSF on LPS-induced cytokine production was found to require 3-day preincubation, and reached a maximum at the concentration of 10(4) U/ml. M-CSF-treated cells responded to a 10 times lower concentration of LPS than control cells in terms of cytokine production. M-CSF was also shown by flowcytometric analysis to influence the expression of CD14, a receptor for LPS, which might render monocytes more sensitive to LPS.

Ruminant cluster CD14

Following the analysis of flow cytometry data on ovine and bovine cells and immunoprecipitation, immunohistochemistry and competitive binding studies, a cluster of three monoclonal antibodies (mAbs) (VPM65, VPM66 and VPM67) appeared to be specific for the ruminant CD14 (Gupta, V.K., McConnell, I., Dalziel, R.G. and Hopkins, J., 1996. Identification of the sheep homologue of the monocyte cell surface molecule-CD14. Vet. Immunol. Immunopathol. in press; Hopkins, J. and Gupta, V.K., 1996. Characterization of 3rd Worshop monoclonal antibodies specific for sheep macrophages/monocytes. Vet. Immunol. Immunopathol., 52:329-339). According to flow cytometry results from human CD14-transfected COS-7 cells and from bovine peripheral blood mononuclear cells, another mAb (CC-G33), not submitted to the Workshop, recognised a bovine CD14 epitope which is conserved in the human CD14 (Sopp, P., Kwong, L.S. and Howard, C.J., 1996. Identification of bovine CD14. Vet. Immunol. Immunopathol., 52: 323-328).

Pore-forming toxins trigger shedding of receptors for interleukin 6 and lipopolysaccharide

Cleavage of membrane-associated proteins with the release of biologically active macromolecules is an emerging theme in biology. However, little is known about the nature and regulation of the involved proteases or about the physiological inducers of the shedding process. We here report that rapid and massive shedding of the interleukin 6 receptor (IL-6R) and the lipopolysaccharide receptor (CD14) occurs from primary and transfected cells attacked by two prototypes of pore-forming bacterial toxins, streptolysin O and Escherichia coli hemolysin. Shedding is not induced by an streptolysin O toxin mutant which retains cell binding capacity but lacks pore-forming activity. The toxin-dependent cleavage site of the IL-6R was mapped to a position close to, but distinct from, that observed after stimulation with phorbol myristate acetate. Soluble IL-6R that was shed from toxin-treated cells bound its ligand and induced an IL-6-specific signal in cells that primarily lacked the IL-6R. Transsignaling by soluble IL-6R and soluble CD14 is known to dramatically broaden the spectrum of host cells for IL-6 and lipopolysaccharide, and is thus an important mechanism underlying their systemic inflammatory effects. Our findings uncover a novel mechanism that can help to explain the long-range detrimental action of pore-forming toxins in the host organism.

Effects of 1,25-dihydroxy vitamin D3 on all-trans retinoic acid sensitive and resistant acute promyelocytic leukemia cells

Following challenge of the acute promyelocytic leukemia (APL) cell line, NB4, with 1, 25 dihydroxy vitamin D3 (1, 25 D3), no increase in the expression of the monocytic surface markers, CD11c, CD14 and HLA-DR is observed. By contrast, 1, 25 D3 increases the expression of CD11b, an early myeloid marker and enhances adherence to plastic following priming of the cells with phorbol 12-myristate 13-acetate (PMA). NB4.306 and NB4.007/6, two all-trans retinoic acid-resistant cell lines originated from NB4 promyelocytes and lacking expression of a complete form of PML-RAR, are totally resistant to 1, 25 D3-dependent induction of CD11b. In addition, NB4.306 cells do not show enhanced plastic adherence following treatment with the vitamin D metabolite and PMA. NB4 and NB4.306 express similar amounts of the transcripts coding for the vitamin D3 receptor and the retinoid accessory receptors, RXR alpha and RXR beta, both in basal conditions and upon treatment with 1, 25 D3.

Cytomegalovirus inhibits CD14 expression on human alveolar macrophages

Cytomegalovirus (CMV) infection in transplant patients is associated with an increased incidence of gram-negative pneumonia; the mechanism for this is unknown. Human alveolar macrophages (HAM) are an important part of the response of the lung to gram-negative bacteria. They interact with lipopolysaccharide (LPS) via the surface receptor CD14. The effect of CMV on CD14 expression by HAM was examined. HAM were obtained from normal volunteers by bronchoalveolar lavage, and some were exposed to CMV. CD14 expression was assessed by immunofluorescent microscopy and flow cytometry. CMV inhibited the surface expression of CD14 on HAM. Release of soluble CD14 was also reduced from infected cells, and Northern blot analysis revealed that CD14 mRNA was reduced in CMV-exposed cells. These findings were specific for CD14 expression. These results demonstrate that CMV inhibits the ability of HAM to express CD14.

Granulocyte-colony stimulating factor, granulocyte-macrophage colony stimulating factor and interleukin 4 induce differentiation in the U-937 human monocytic leukemia cell line

We studied the effect of TPA, G-CSF, GM-CSF, conditioned medium from 5637 cells (CM5637) and IL-4 on U-937 cell line proliferation and differentiation. Flow cytometry analysis showed that the expression of the CD14 cell surface antigen, initially detected in 90% of the cells, decreased when the cells were cultured with either G-CSF, GM-CSF, CM5637, or IL-4. The CD11c expression only decreased by exposure to GM-CSF and IL-4. The cells also showed a decrease in alpha-naphthylesterase (alpha-NAE) activity and an increase in peroxidase (Px) activity in the GM-CSF supplemented cultures. Remarkable changes in cell morphology were also observed. IL-4 induced morphologic features resembling histiocytic-like cells positive for the expression of alpha-NAE and negative for Px. GM-CSF induced cells with pseudopods, negative for alpha-NAE expression and positive for Px. TPA effect on U-937 cells was similar to that observed with GM-CSF. No proliferative response was detected with any of the factors assayed. These results suggest that GM-CSF and IL-4 can promote distinct changes in the differentiative pathway of U-937 cells, as evidenced by the marked morphological, immunological and cytochemical changes observed in the cell cultures.

Inability of the Francisella tularensis lipopolysaccharide to mimic or to antagonize the induction of cell activation by endotoxins

We studied the ability of the lipopolysaccharide (LPS) extracted from a vaccine strain of Francisella tularensis (LPS-Ft) to mimic LPSs from other gram-negative bacteria for activation of various murine cell types or to antagonize the effects of other LPSs. We found that activation of macrophages for the production of tumor necrosis factor alpha and NO, of pre-B lymphocytes for the expression of surface immunoglobulins, and of bone marrow cells for the expression of LPS-binding sites was either undetectable with LPS-Ft or required concentrations 100 to 1,000 times higher than for standard LPSs. Preexposure of macrophages to LPS-Ft also failed to trigger down-regulation of tumor necrosis factor alpha (desensitization) or up-regulation of NO responses to an endotoxin challenge. In contrast to other atypical LPSs, LPS-Ft was also unable to antagonize any of the endotoxin-induced cellular responses mentioned above, suggesting that this LPS does not interact with LPS receptors.

Differences in the state of differentiation of THP-1 cells induced by phorbol ester and 1,25-dihydroxyvitamin D3

Human THP-1 leukemia cells differentiate along the monocytic lineage following exposure to phorbol-12-myristate-13-acetate (PMA) or 1,25-dihydroxyvitamin D3 (VD3). In the monocytic cell line THP-1, PMA treatment resulted in a more differentiated phenotype than VD3, according to adherence, loss of proliferation, phagocytosis of latex beads, and expression of CD11b and CD14. Both differentiating substances induced similar effects in the release of superoxide anions (O2-). VD3-differentiated cells did not release prostaglandin E2 (PGE2), in contrast to PMA-differentiated cells, and in PMA-differentiated cells phospholipase A2 (PLA2) activity and expression was increase. Lipopolysaccharide (LPS)-stimulated tumor necrosis factor-alpha (TNF-alpha) release was higher in PMA-treated cells. PMA- but not VD3-differentiation resulted in a translocation of protein kinase C (PKC) isoenzymes to membrane fractions. Both differentiating agents up-regulated the expression of PKC isoenzymes. Whereas VD3 elevated mainly the expression of PKC-beta, PMA caused a strong increase in PKC-delta and a weak increase in PKC-alpha, PKC-epsilon, and PKC-zeta expression. These results indicate that phorbol ester and the active metabolite of vitamin D induce different signal pathways, which might result in different achievement of differentiation.

Intramammary defense against infections induced by Escherichia coli in cows

OBJECTIVE

To examine Escherichia coli lipopolysaccharide (LPS) effects on expression of CD14 and CD18 cell surface receptors and lectin/carbohydrate-mediated nonopsonic phagocytosis of E coli.

DESIGN

Cell isolation, monoclonal antibody, phagocytosis, and flow cytometric studies.

ANIMALS

4 clinically normal lactating Holstein cows for studies on CD14 and CD18, and 2 for phagocytosis studies.

PROCEDURE

Binding of CD14 and CD18 monoclonal antibodies to blood and milk neutrophils and mononuclear leukocytes was studied by flow cytometry before and after intramammary injection of LPS, and nonopsonic phagocytosis of E coli by blood neutrophils was determined. Presence of intracellular CD14 was determined after in vitro incubation of neutrophils in skimmed milk and after fixation and permeabilization of freshly isolated neutrophils.

RESULTS

Before LPS injection, percentages of blood neutrophils and large mononuclear (LMO) cells expressing CD14 averaged 3 and 63% and 68 and 35% for mammary neutrophils and LMO cells, respectively. After LPS injection, CD14 was only detected on blood and mammary LMO cells (61 and 25%); receptor expression increased by 1.8- and threefold, respectively. In vitro incubation of neutrophils in skimmed milk increased the percentage of neutrophils expressing CD14. The number of blood neutrophils staining positive for CD14 increased after permeabilization of the plasma membrane, which was blocked by unlabeled anti-CD14 monoclonal antibodies. Before LPS, percentages of blood neutrophils and LMO cells expressing CD18 averaged 93 and 95% and was 88 and 55% for mammary neutrophils and LMO cells, respectively. After LPS, percentages of mammary neutrophils and LMO cells expressing CD18 increased to 100 and 95%, respectively. Expression of CD18 was 2.6-fold higher for mammary neutrophils before injection of LPS, compared with blood neutrophils, either before or after LPS. In absence of opsonins, neutrophils with adherent and phagocytosed E coli averaged 83 and 14%.

CONCLUSIONS

LPS modulated expression of CD14 and CD18 and lectin-carbohydrate interactions mediated nonopsonic phagocytosis of E coli. An intracellular pool of CD14 exists in bovine neutrophils and is capable of translocating to the cell surface.

CLINICAL RELEVANCE

Development of methods to maximize expression of CD14 receptors on mammary neutrophils involved in production of tumor necrosis factor-alpha, and nonopsonic phagocytosis could result in reducing prevalence of mastitis in dairy cows.

Low infection frequency of macrophages in the spleens of HIV+ patients

Macrophages are often considered as a reservoir of latent infection in HIV+ patients, and their infection may indeed be very important functionally. However, some quantitative studies did not find high infection frequencies in peripheral blood monocytes. Since lymphoid organs are the major site of infection, macrophage infection was tested in spleens removed from HIV+ patients for treatment of different syndromes. Ten replicates of limiting dilutions from different cell populations were submitted to a nested PCR specific to conserved regions of HIV1 env DNA. On an average, 1/2,300 adherent cells carried HIV1 DNA (n = 7; range: 1/55,000 to 1/660). These adherent cells, obtained after two days of culture, comprised the whole macrophage population, with no biases introduced by surface molecule selection, but were not pure (41-78% macrophages). Only 1/37,000 CD14+ monocyte/macrophages were positive (n = 6; range: 1/130,000 to 1/22,000). Therefore, the infection frequency of the isolated splenic monocytes/macrophages from these patients could be estimated at between 1/37,000 and 1/2,300. In contrast, 1/60 CD4+ T lymphocytes were positive (n = 7; range: 1/190 to 1/17). Within the experimental limits, such as cell isolation, required for accurate quantification, this study in the spleen indicates, as have other studies on peripheral blood, that macrophages do not quantitatively constitute an important reservoir of HIV when compared to CD4+ T lymphocytes.

Expression of the p53 tumor suppressor gene induces differentiation and promotes induction of differentiation by 1,25-dihydroxycholecalciferol in leukemic U-937 cells

Leukemic U-937 cells, which lack normal p53, were stably transfected with a temperature-sensitive mutant of p53 to investigate the consequences for growth and differentiation. On induction of wild-type p53 activity at the permissive temperature, some of these cells underwent maturation as judged by the capacity for oxidative burst and the appearance of monocyte related cell surface molecules. Moreover, wild-type p53-expressing cells were more sensitive than p53-negative control cells to induction of differentiation by 1,25-dihydroxycholecalciferol; a twofold to fourfold increase of the fraction of cells showing signs of terminal maturation was observed when wild-type p53-expressing cells were incubated with 1,25-dihydroxycholecalciferol at concentrations that only slightly affected control cells. Whereas wild-type p53 activity per se induced maturation of certain cells, other underwent cell death judging from the reduced capability to exclude trypan blue and the appearance of fragmented DNA in flow cytometric analysis. The p53-induced cell death could be inhibited by incubation with 1,25-dihydroxy-cholecalciferol, but not all-trans retinoic acid. Thus, 1,25-dihydroxycholecalciferol, seemed to increase the survival of wild-type p53-expressing cells and to cooperate with wild-type p53 to induce differentiation. The data imply that p53-mediated maturation in U-937 cells depends on optimal regulation of signals for differentiation, survival and proliferation, and suggest a role for p53 in the differentiation induction of leukemic cells.

Transcriptional activation of the Cdk inhibitor p21 by vitamin D3 leads to the induced differentiation of the myelomonocytic cell line U937

The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3, acting through its cognate nuclear receptor (vitamin D3 receptor, VDR) will induce myeloid leukemic cell lines to terminally differentiate into monocytes/macrophages. Because VDR acts by transcriptionally regulating responsive genes in a ligand-dependent manner, we sought target genes of the receptor that initiate, the differentiation process in response to ligand. We screened a cDNA library prepared from the myelomonocytic U937 cell line with probes generated from either 1,25-dihydroxyvitamin D3-treated or untreated cells. We report here that a candidate clone that hybridized differentially is the Cdk inhibitor p21WAF1, CIP1. Furthermore, we show that p21 is transcriptionally induced by 1,25-dihydroxyvitamin D3 in a VDR-dependent, but not p53-dependent, manner, and we identify a functional vitamin D response element in the p21 promoter. Transient overexpression of p21 and/or the related Cdk inhibitor p27 in U937 cells in the absence of 1,25-dihydroxyvitamin D3 results in the cell-surface expression of monocyte/macrophage-specific markers, suggesting that ligand-modulated transcriptional induction of the p21 gene facilitates the induced differentiation of this monoblastic cell line. We believe that this is the first report demonstrating that the ectopic overexpression of a Cdk inhibitor such as p21 or p27 directly leads to a terminal differentiation program.

Leukocyte CD14 and CD45 expression during hemodialysis: polysulfone versus cuprophane

The expression of CD14 on monocytes and CD45 on monocytes and granulocytes was evaluated during hemodialysis by flow cytometric analysis in the 'resting state' and after in vitro stimulation with phorbol myristate acetate (PMA). A comparison of complement activating cuprophane (CU) versus less complement activating polysulfone (PS) was undertaken. 'Resting state' CD45 expression on granulocytes increased markedly during CU dialysis compared to time 0, whereas this rise was only moderate with PS (CU vs. PS, p < 0.01). When considering the increase in expression upon PMA stimulation, a lower value was obtained during CU dialysis for both CD14 (monocytes at 60 and 240 min) and for CD45 (monocytes and granulocytes at 15 min). In conclusion, granulocytes in the 'resting state' expressed more CD45 on their cell membranes during CU dialysis, whereas CD14 and CD45 upregulation after ex vivo addition of PMA was blunted during CU dialysis.

Expression of lymphocyte function-associated antigen 3 in oral lichen planus

OBJECTIVE

The expression pattern of lymphocyte function-associated antigen 3 (LFA-3) in the buccal mucosa of oral lichen planus (OLP) patients was compared to that of healthy controls to investigate the possible role of LFA-3 in cell interactions within OLP lesions.

MATERIALS AND METHODS

Samples of buccal mucosa from 17 clinically healthy individuals and 17 OLP lesions were analysed. Expression of LFA-3, CD2, CD3 and CD14 was visualized by an immunoperoxidase technique and assessed microscopically.

RESULTS

In healthy buccal mucosa LFA-3 was expressed on keratinocytes, Langerhans cells within the epithelium and on endothelial cells in the lamina propria. In OLP patients a similar pattern of LFA-3 staining was observed. In addition, cytoplasmic LFA-3 without accompanying surface staining, was seen on a subpopulation of macrophage-like cells. Substantial amounts of LFA-3 also appeared to be associated with non-cellular components of the extracellular matrix within the inflammatory infiltrate.

CONCLUSIONS

We have obtained evidence for a previously undescribed localization of LFA-3 within macrophages, and have observed that expression of LFA-3 is apparently elevated within OLP lesions. LFA-3 may play an important role in the pathogenesis of OLP.

Growth parameters and rate of expression of some CD markers in sorted and not sorted macrophage cultures

Several parameters of in vitro culturing were investigated for two kinds of human macrophages cell fractions, i.e. sorted by flow cytometry and not sorted, as follows:--growth ability during serial in vitro passages, and--percent rate of CD13, CD14 and CD33 expression at different in vitro passage levels. Results point out the ability of sorted cells to survive to a higher number of serial passages. A dramatical loss of CD13 and especially CD33 markers was noticed during culturing within the not sorted cells, as compared to homologous sorted ones.