Identification of membrane antigen C33 recognized by monoclonal antibodies inhibitory to human T-cell leukemia virus type 1 (HTLV-1)-induced syncytium formation: altered glycosylation of C33 antigen in HTLV-1-positive T cells.

We isolated four monoclonal antibodies (MAbs), M38, M101, M104, and C33, which were capable of inhibiting syncytium formation induced in a human T-cell line, MOLT-4-#8, by coculture with human T-cell leukemia virus type 1 (HTLV-1)-positive human T-cell lines. The MAbs had, however, no inhibitory activity on syncytium formation induced in a human osteosarcoma line, HOS, by HTLV-1-positive T-cell lines. They also did not inhibit syncytium formation induced in MOLT-4-#8 by human immunodeficiency virus type 1-positive MOLT-4. All MAbs reacted with various human cell lines of lymphoid and nonlymphoid origins, including HTLV-1-positive T-cell lines. Furthermore, they all reacted with a murine A9 clone containing human chromosome 11 fragment q23-pter. Two MAbs, M104 and C33, immunoprecipitated a membrane antigen with the same molecular size. The antigen (henceforth called C33 antigen) was about 40 to 55 kDa in HTLV-1-negative Jurkat, CEM, MOLT-4, and normal peripheral blood CD4-positive human T cells and about 40 to 75 kDa in HTLV-1-positive C91/PL, TCL-Kan, MT-2, and in fresh HTLV-1-transformed CD4-positive human T-cell lines. Pulse-chase experiments revealed that C33 antigen was synthesized as a 35-kDa precursor that was then processed to 41 to 50 kDa in MOLT-4 and to 44 to 70 kDa in C91/PL. In the presence of tunicamycin, a 28-kDa protein was synthesized. The conversion from 35 kDa to 41 to 50 kDa in MOLT-4 and to 44 to 70 kDa in C91/PL was inhibited by monensin. Treatment with N-glycanase alone, but not with sialidase and O-glycanase in combination, completely removed the sugar moiety of C33 antigen from both HTLV-1-negative Jurkat and HTLV-1-positive C91/PL. Therefore, C33 antigen has only N-linked carbohydrates, the modification of which appears to be substantially altered in the presence of the HTLV-1 genome.     

S-100-positive T cells are largely restricted to a CD8-positive, 9.3-negative subset

The present report concerns the demonstration of the exclusive detection among peripheral blood T-lymphocytes of the S-100 protein within the CD8-positive subpopulation which lacks the antigen recognized by the 9.3 monoclonal antibody. Highly purified human peripheral blood T-cell subsets, obtained by means of panning techniques, were first stained, by an immunofluorescence method, with purified anti-S-100 protein antibodies. The vast majority of S-100 protein- (and, specifically, its beta subunit) positive cells were detected in the CD8-positive, 9.3-negative subset. This subset had previously been shown to comprise all the alloantigen-specific and histamine-inducible suppressor T-cells. Other T-subsets, even those showing either CD8-positivity (but 9.3-positivity) or 9.3-negativity (but CD8-negativity), were, as a rule, S-100 negative. Immunoelectronmicroscopy confirmed that the S-100-positive cells, showing peroxidase activity within the cytoplasm, were found exclusively within the CD8-positive, 9.3-negative subset. This finding of S-100 protein in cells of a specific T8 suppressor subset extends the range of the known distribution of this protein and may have important implications concerning its role in the modulation of immune responses.     

Activation of T cells through a T cell-specific epitope of CD45.

The 180- and 190-kDa isoforms of CD45 are preferentially expressed on the helper inducer (memory) subset of CD4 cells. In order to generate monoclonal antibodies against the extracellular domains of these isoforms and determine whether they could regulate the function and activation of these cells, we developed a mAb, anti-4H2D, by immunizing Balb/c mice with an isogenic mouse pre-B cell line expressing the human 190-kDa CD45 isoform. Anti-4H2D reacts with approximately 60% of T cells, 70% of CD4 cells, and 60% of CD8 cells. The CD4 cell population defined by this mAb corresponds functionally and phenotypically to that defined by the CD45RO+CD29+ subset. Western blotting demonstrated that anti-4H2D reacts primarily with the 190-kDa isoform of CD45 and to a minor extent, the 205- and 180-kDa CD45 isoforms. Interestingly, this mAb reacted with only a subpopulation of mature thymocytes and peripheral T cells, despite the fact that the 190-kDa CD45 isoform, as well as CD45RO and CD29, is more widely distributed on cells of hematopoietic origin. The 4H2D epitope was neuraminidase sensitive, indicating that anti-4H2D reacts with a carbohydrate epitope which is present on only a subset of the T cells containing the 190-kDa CD45 isoform epitopes. Functional studies showed that soluble anti-4H2D augmented T cell proliferation induced by the CD2 and CD3 pathways, and treatment of T cells with this mAb up-regulated [Ca2+]i flux induced by both anti-CD2 and anti-CD3 mAbs. These results suggest that the 190-kDa CD45 isoform on human CD4 cells is heterogeneous and that the 190-kDa isoform recognized by anti-4H2D regulates the function and activation of CD4 helper T cells.     

Human eosinophils express CR1 and CR3 complement receptors for cleavage fragments of C3

The functional and antigenic characteristics of C3 receptors expressed on human eosinophils were investigated using rosette assays with sheep erythrocytes coated with C3 fragments and flow cytometric analysis of cells stained with anti-receptor antibodies. Purified peripheral blood eosinophils from 13 patients with hypereosinophilia expressed CR1 antigens. In 8 patients, a mean of 14 + 9.5% eosinophils formed C3b-dependent rosettes that were inhibited by F(ab')2 anti-CR1 antibodies. This number increased to 33% following stimulation with leukotriene B4 (LTB4) (10(-7) M). Similar numbers of C3b rosettes were formed by hypodense and normodense eosinophils. Eosinophils from 2 patients from this group expressed 20,000 125I-labeled monoclonal anti-CR1 antibody binding sites/cell. In another group of patients, 55 +/- 9% eosinophils spontaneously formed C3b-dependent rosettes that could not be enhanced by LTB4. In all patients, a mean of 16 +/- 9% eosinophils formed cation-dependent rosettes with C3bi-bearing intermediates that were inhibited by anti-CR3 antibody OKM1. All eosinophils stained with monoclonal antibodies against the alpha chain of CR3. There was no C3d-dependent rosette formation with eosinophils and no eosinophils stained with monoclonal anti-CR2 antibody. Thus, human eosinophils express CR1 and CR3. Since CR3 is required for the adhesion of granulocytes to surfaces and antibody-dependent cellular cytotoxicity of neutrophils, the interaction of C3 fragments with CR3 and CR1 on eosinophils may be of importance in eosinophil-mediated damage of opsonized targets.     

Melanoma cell expression of CD200 inhibits tumor formation and lung metastasis via inhibition of myeloid cell functions

CD200 is a cell surface glycoprotein that functions through engaging CD200 receptor on cells of the myeloid lineage and inhibits their functions. Expression of CD200 has been implicated in a variety of human cancer cells including melanoma cells and has been thought to play a protumor role. To investigate the role of cancer cell expression of CD200 in tumor formation and metastasis, we generated CD200-positive and CD200-negative B16 melanoma cells. Subcutaneous injection of CD200-positive B16 melanoma cells inhibited tumor formation and growth in C57BL/6 mice but not in Rag1^−/−C57BL/6 mice. However, i.v. injection of CD200-positive B16 melanoma cells dramatically inhibited tumor foci formation in the lungs of both C57BL/6 and Rag1^−/−C57BL6 mice. Flow cytometry analysis revealed higher expression of CD200R in Gr1⁺ myeloid cells in the lung than in peripheral myeloid cells. Depletion of Gr1⁺ cells or stimulation of CD200R with an agonistic antibody in vivo dramatically inhibited tumor foci formation in the lungs. In addition, treatment with tumor antigen specific CD4 or CD8 T cells or their combination yielded a survival advantage for CD200 positive tumor bearing mice over mice bearing CD200-negative tumors. Taken together, we have revealed a novel role for CD200-CD200R interaction in inhibiting tumor formation and metastasis. Targeting CD200R may represent a novel approach for cancer immunotherapy.     

The restricted expression of granzyme M in human lymphocytes

We have analyzed the expression of human granzyme M (Gzm M) in various human leukocyte subsets using the specific mAb 4H10. Using FACS and Western blotting analysis we compared the expression of Gzm M with that of other granzymes (Gzm A and Gzm B) and the lytic protein perforin. Human Gzm M was constitutively highly expressed in NK cells as was perforin and Gzm A. Surprisingly, freshly isolated NK cells had very low (sometimes undetectable) levels of Gzm B. In contrast to Gzm B and perforin, Gzm M was not detected in highly purified CD4(+) and CD8(+) T cells either constitutively or after short term activation in vitro. However, low levels of Gzm M were observed in some T cell clones on prolonged passage in vitro. Gzm M was not detected in highly purified neutrophils, monocytes, or tumor cells of the myelomonocytic lineage. Examination of minor T cell subsets from human peripheral blood showed detectable Gzm M in CD3(+), CD56(+) T cells and gammadelta T cells. A histological staining procedure was developed that demonstrated a granular staining pattern for Gzm M and a cellular distribution similar to that observed by Western blotting. These data indicate that the expression of Gzm M does not always correlate with the lytic activity of cytotoxic cells. However, expression of Gzm M in NK cells, CD3(+), CD56(+) T cells, and gammadelta T cells suggests that this enzyme may play some role in innate immune responses.     

Isolation and characterization of a monoclonal antibody that inhibits HIV-1 infection

To identify a cell surface molecule other than CD4 involved in infection of cultured cells with human immunodeficiency virus type 1 (HIV-1), mice were immunized with the CD4-negative Raji human B-cell line in order to isolate a monoclonal antibody (mAb). We isolated mAb 33A, which inhibited the infection of CD4-positive T cells, B cells, human peripheral blood lymphocytes (PBL), and brain-derived cells with HIV-1. Formation of viral DNA was also blocked when CD4-positive Raji cells were treated with 33A after adsorption of HIV-1, but not before its adsorption. mAb 33A had little effect on syncytium formation induced by cocultivation with HIV-1-producing cells. Flow cytometry revealed that 33A reacted with HTLV-I-positive T-cell lines, Burkitt's lymphoma cell lines, phytohemagglutinin (PHA) -stimulated PBL, brain-derived fibroblast-like cells, and some adherent cell lines, but hardly at all with immature T-cell lines. Immunoblotting experiments showed that 33A recognized an antigen with an apparent molecular mass of 32 kDa, but did not recognize chemokine receptors such as CXCR4, CCR5, or CCR3. The distribution characteristic of the antigen recognized by 33A on various cells and its molecular weight suggest that mAb 33A recognizes a new cellular antigen that is necessary for HIV-1 entry.     

Morphometric evaluation of CD16-positive cells with respect to CD2 antigen coexpression

We examined morphometric as well as functional characteristics of CD16-positive human peripheral blood lymphocytes on the basis of the coexpression of the CD2 antigen. For morphometric analyses, nuclear area and cellular area were determined by counting line cross-points of a superimposed quadratic lattice test system overlying nuclei and the whole cell, respectively. Moreover, to evaluate the cellular villousity degree, the maximum inscrible circle and an irregular polygon were inscribed within cell profiles. The cytoplasm fraction included between the plasmalemma and the traced irregular polygon was considered as the villous portion of the cell. Finally, the NK capability was measured in a 6-hr 51Cr-release assay with human K-562 myeloid cells as targets. Within the CD16-positive cell population, the CD16-positive/CD2-negative cells seem to represent the most efficient NK cell subset. To the higher NK capability correspond a higher villousity degree and a lower nuclear area/cellular area ratio of the CD2-negative/CD16-positive subset, when compared with CD2-positive/CD16-positive cells.     

Specific leukotriene formation by purified human eosinophils and neutrophils

Human granulocytes isolated from peripheral blood have been described to synthesize both LTB4 and LTC4 from arachidonic acid. We have observed that the amount of LTC4 produced by human granulocyte preparations is strongly dependent on the relative amount of eosinophils. To investigate a possibly significant difference in leukotriene synthesis of the eosinophilic and neutrophilic granulocytes, we developed a purification method to isolate both cell types from granulocytes obtained from the blood of healthy donors. Leukotrienes were generated by incubation of the purified cells with arachidonic acid, calcium ionophore A23187, calcium-chloride and reduced glutathione. Surprisingly, eosinophils were found to produce almost exclusively the spasmogenic LTC4. In contrast, neutrophils produce almost exclusively the chemotactic LTB4, its omega-hydroxylated metabolite 20-hydroxy-LTB4 and two non-enzymically formed LTB4 isomers.     

Novel technique for the direct flow cytofluorometric analysis of human basophils in unseparated blood and bone marrow, and the characterization of phenotype and peroxidase of human basophils

BACKGROUND: No technique has been reported to analyze directly the antigen expression on basophil leukocytes when using a flow cytometer; therefore, the exact phenotype of human basophils and the character of the peroxidase in basophils are not well understood. METHODS: Human blood basophils were purified by using an antibody against high-affinity Fc epsilon receptor (hFcepsilonR) and a MACS magnetic cell sorting system and then cytochemically stained. The phenotype and peroxidase of the human basophils were flow cytofluorometrically analyzed directly in unseparated blood and bone marrow samples as hFcepsilonR+/MBP+ (major basic protein)/Hist+ (histamine) light-density cells distributed in the high sidescatter area of lymphocytes on light scattergrams. RESULTS: The peroxidase granules of human basophils were stained by an anti-eosinophil peroxidase (EPO) antibody. The human blood basophils had common granulocyte markers plus CD25, i.e., they were CD11a/ CD11b/CD11c/CD25/CD38/CD13/CD33/hFcepsi lonR/MBP/Hist/ EPO positive, CD71 dim positive, CD14/CD15 partially positive, and CD2/CD3/CD7/CD122/CD16/CD56/CD57/ CD10/CD19/CD20/CD22/HLA-DR/MPO (myeloperoxidase)/CD23 negative. Further examination was done to analyze the expression of colony-stimulating factor receptors on three lineages of granulocytes, i.e., basophils, eosinophils, and neutrophils. The neutrophils were CD114 (G-CSFR)/CD116 (GM-CSFR)/CD124 [interleukin (IL)-4R]/CD126 (IL-6R) positive and CD123 (IL-3R)/CD125 (IL-5R) negative. In contrast, the eosinophils and basophils were CD116/CD123/CD125/CD126 positive and CD114/CD124 negative. CONCLUSIONS: This novel technique for directly characterizing human basophil leukocytes with flow cytometry may be a convenient way to screen the expression of surface antigens and the cytoplasmic expression of CD antigens and other proteins in human blood basophils and to analyze alterations of the character of basophils by cytokines and other biological substances in vivo and in vitro.     

Functional characterization of ecto-5'-nucleotidase-positive and -negative human T lymphocytes

Functional studies were performed on human peripheral blood T lymphocytes stained with goat anti-5'-nucleotidase antibodies and separated into ecto-5'-nucleotidase (ecto-5'-NT)-positive and -negative populations using the FACSTAR fluorescence-activated cell sorter. On the average, ecto-5'-NT+ T cells contained 34 +/- 13% CD4+ and 55 +/- 15% CD8+ cells, whereas ecto-5'-NT-T cells contained 65 +/- 12% CD4+ and 23 +/- 8% CD8+ cells. Staining with anti-5'-NT antibodies did not significantly alter the ability of unseparated T cells to proliferate in response to PHA or PMA, or in a MLR. However, prior incubation with anti-5'-NT antibodies did inhibit the ability of irradiated T cells to provide help for PWM-stimulated Ig synthesis by as much as 55%. In five separate experiments, ecto-5'-NT-T cells demonstrated an equal or better ability to incorporate [3H]TdR after PHA stimulation or in a MLR, as compared with ecto-5'-NT+ T cells. Similarly, ecto-5'-NT- T cells were not diminished in their ability to provide help for autologous B cells in a PWM-driven system. Clearly, the inability of ecto-5'-NT- T cells from patients with a variety of immunodeficiency diseases to function in these assays cannot be explained solely by their lack of ecto-5'-NT activity. In contrast, ecto-5'-NT-positive and -negative T cells showed markedly different dose-response curves for proliferation in response to PMA. Ecto-5'-NT+ T cells responded to lower doses of PMA (1.0 ng/ml) than did ecto-5'-NT- T cells and showed a two- to eight-fold greater rate of [3H]TdR incorporation at 3 to 10 ng of PMA per ml. Ecto-5'-NT+ T cells may have a protein kinase C that is more accessible or more easily activated or may utilize an alternate pathway of activation when stimulated with low concentrations of PMA.     

Distribution of ecto-5'-nucleotidase on subsets of human T and B lymphocytes as detected by indirect immunofluorescence using goat antibodies

Human T and B lymphocyte subsets were characterized for ecto-5'-nucleotidase (ecto-5'-NT) expression by two-color immunofluorescence by using polyclonal goat antibodies to 5'-NT and murine monoclonal antibodies to T and B cell subsets. Anti-5'-NT antibodies were prepared by immunizing a goat with purified human placental 5'-NT. Lymphocyte surface 5'-NT was detected with F(ab')2 fragments of immune goat IgG followed by biotinylated F(ab')2 rabbit anti-goat IgG and fluorescein isothiocyanate-avidin. Lymphocyte cell surface antigens were detected with phycoerythrin (PE)-conjugated anti-CD3, anti-CD4, anti-CD8, anti-CD16, and anti-CD19. HB-4, an antigen present on a major subset of human peripheral blood B cells, was detected with murine monoclonal anti-HB-4 and PE-anti-mouse-kappa. Analysis showed that ecto-5'-NT was expressed on 32 +/- 7% of CD3+, 19 +/- 6% of CD4+, and 50 +/- 21% of CD8+ T cells, but not on CD16+ lymphocytes. Ecto-5'-NT was also expressed on 81 +/- 8% of adult peripheral blood B cells as defined by PE-anti-CD19; HB-4 was expressed on 84 +/- 7% of CD19+ cells. The two populations of B cells were not identical, however, because HB-4 was co-expressed on only 79 +/- 18% of ecto-5'-NT+ B cells. Two-color immunofluorescent staining of T cells from a patient with congenital agammaglobulinemia and low T cell ecto-5'-NT activity revealed reduced percentages of ecto-5'-NT+ cells in his CD3+, CD4+, and CD8+ populations. Thus, reduced ecto-5'-NT activity by enzyme assay was paralleled by reduced numbers of 5'-NT molecules on the cell surface. Two-color immunofluorescent staining of B cells from a patient with hypogammaglobulinemia and low B cell ecto-5'-NT activity also revealed markedly reduced expression of 5'-NT. HB-4 expression was normal, however, suggesting that the patient's B cells were blocked in maturation subsequent to the acquisition of HB-4 but prior to that of ecto-5'-NT. These results demonstrate that anti-5'-NT antibodies will be valuable tools for analyzing ecto-5'-NT expression and lymphocyte maturation in patients with immuno-deficiency diseases.     

The HML-1 antigen of intestinal lymphocytes is an activation antigen.

The Ag recognized by the mAb HML-1 is expressed on more than 90% of human intestinal intraepithelial lymphocytes, whereas in other lymphoid tissues it is rarely or not expressed. In the present study, we have investigated the percentage of HML-1-positive cells in the human intestinal lamina propria and the coexpression of HML-1 with different T cell subset markers. In addition, we studied the inducibility of HML-1 on PBL which normally are HML-1-negative. Flow cytometric analysis of isolated intestinal lamina propria lymphocytes (LPL) showed that about 40% of the cells expressed HML-1, the majority belonging to the CD8-positive subpopulation. Virtually all LPL expressed CD45RO, whereas the percentage of CD29-positive cells was only about 50%, similar to PBL. There were only few cells expressing CD45RA or Leu-8 in the lamina propria. HML-1-positive cells were almost exclusively CD45RA-negative, but were found in both the CD29-positive and the CD29-negative subpopulation of LPL. In vitro stimulation of PBL showed that the expression of HML-1 was inducible on T cells by mitogens, phorbolester, Ag, and rIL-2. Expression of HML-1 was induced with a different time course and with differences in the response to the investigated stimuli compared with CD25. Activated HML-1-positive PBL were also predominantly CD45RA-negative. The findings show that HML-1 is an Ag, which is expressed in vivo on a specific subset of previously activated T cells in the unique environment of the intestinal mucosa, and which can be induced in vitro by different activation signals on PBL.     

A subpopulation of bone marrow cells depleted by a novel antibody, anti-Liv8, is useful for cell therapy to repair damaged liver

We previously reported a new in vivo model named as "GFP/CCl(4) model" for monitoring the transdifferentiation of green fluorescent protein (GFP) positive bone marrow cell (BMC) into albumin-positive hepatocyte under the specific "niche" made by CCl(4) induced persistent liver damage, but the subpopulation which BMCs transdifferentiate into hepatocytes remains unknown. Here we developed a new monoclonal antibody, anti-Liv8, using mouse E 11.5 fetal liver as an antigen. Anti-Liv8 recognized both hematopoietic progenitor cells in fetal liver at E 11.5 and CD45-positive hematopoietic cells in adult bone marrow. We separated Liv8-positive and Liv8-negative cells and then transplanted these cells into a continuous liver damaged model. At 4 weeks after BMC transplantation, more efficient repopulation and transdifferentiation of BMC into hepatocytes were seen with Liv8-negative cells. These findings suggest that the subpopulation of Liv8-negative cells includes useful cells to perform cell therapy on repair damaged liver.     

Reactivity of rabbit antiserum to guinea pig eosinophils.

Although the eosinophil has been recognized as a distinctive cell type for almost 100 years, the major functions of these cells remain unknown. As an approach to defining these functions we have treated guinea pigs with rabbit antiserum to eosinophils (AES) in an attempt to ablate these cells from tissues. Rabbits were immunized thrice with purified eosinophils and the antisera were absorbed with peripheral blood cells from guinea pigs made eosinopenic with methyprednisolone to remove antibodies reactive with serum proteins and erythrocytes. The resulting sera reacted strongly with eosinophils in cytotoxicity tests and had weak or no reactivity with neutrophils. However, absorption of AES with purified neutrophils removed antieosinophil activity. Intraperitoneal injection of potent AES into guinea pigs resulted in complete absence of eosinophils from the peripheral blood and from the peritoneal cavity with only transient or no reduction in circulating neutrophils. Eosinophils were also reduced in bone marrow, spleen, and intestine. The ability of neutrophils to absorb AES activity in spite of weak reactivity in cytotoxicity tests may reflect a quantitative difference in antigenic determinants between eosinophils and neutrophils.     

A Monoclonal Antibody Modulates Neutrophil Adherence While Enhancing Cell Motility

A monoclonal antibody (MoAb) to human neutrophils, designated 3H9, was established by screening for the inhibition of neutrophil adherence to plastic plates containing a medium supplemented with fetal calf serum (FCS medium). The antigen recognized by 3H9 was shown to be present on human leukocytes and found at the highest levels on granulocytes. On Western blotting, 3H9 reacted with a molecule having a molecular weight of 80 kDa. When this MoAb was added at the same time as a neutrophil stimulant (fMLP), the inhibition of neutrophil adherence to plastic plates in the presence of FCS medium was observed after 60 min incubation. Furthermore, this MoAb enhanced not only fMLP-induced chemotaxis but random migration of neutrophils as well. The mechanisms of these phenomena are discussed.     

A new method for the purification of human eosinophils and neutrophils, and a comparison of the ability of these cells to damage schistosomula of Schistosoma mansoni.

Centrifugation of human white blood cells over either Ficoll-Hypaque or slightly hypertonic Metrizamide discontinuous gradients reliably produces separate fractions that are enriched for either neutrophilic or eosinophilic granulocytes. This single step purification routinely yields 90 to 100% pure neutrophils and 85 to 100% pure eosinophils. Metrizamide gradients, in particular, reproducibly provide high yields of 90 to 100% pure eosinophils from normal subjects with 2 to 3% eosinophils in their peripheral blood. The method does not damage cells as judged by morphologic or functional criteria. The purified cell populations were tested for their ability to damage antibody-coated schistosomula either by the measurement of 51Cr release from labeled organisms, or by direct morphologic assessment. Neutrophils were superior in their ability to release 51Cr from labeled organisms, but eosinophils adhered to the organisms to a greater extent and induced microscopically detectable damage.     

Induction of CD69 activation molecule on human neutrophils by GM-CSF,IFN-gamma,and IFN-alpha

The CD69 glycoprotein is an early activation antigen of T and B lymphocytes but it expression is induced in vitro on cells of most hematopoietic lineages, including neutrophils after stimulation with PMA or fMLP. In this study, we investigated whether CD69 expression on human neutrophils could be modulated by inflammatory or anti-inflammatory cytokines (IL-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, G-CSF, GM-CSF, TNF-alpha, TGF-beta, IFN-alpha, IFN-gamma). Resting neutrophils from healthy subjects did not express CD69 on the cell surface; moreover, a preformed intracellular pool of CD69 was not evident in these cells. CD69 was barely detectable on these cells after overnight incubation in medium while overnight incubation with GM-CSF, IFN-gamma or IFN-alpha significantly induced CD69 expression on neutrophils with GM-CSF appearing to be the most potent inducer. This induction was dependent on a new protein synthesis as it was significantly inhibited by cycloheximide (about 50% inhibition). CD69 cross-linking on GM-CSF-primed neutrophils sinergized with LPS and increased TNF-alpha production and secretion suggesting a role for CD69-positive neutrophils in the pathogenesis and maintenance of different inflammatory diseases.