An anti-human monocyte/macrophage monoclonal antibody, reacting most strongly with macrophages in lymphoid tissue

In this report, we have described monoclonal antibody (mAb) 24 which bound specifically to a 174,000 polypeptide present on 45 +/- 16% of human monocytes. Expression of the 24 molecule increased on monocytes when they were cultured. When tissues were examined using immunohistochemical techniques, macrophages (Mph) associated with skin and with lymphoid organs strongly expressed the mAb 24 molecule, whereas, Mph in nonlymphoid organs were only weakly positive. mAb 24 reacted with cells of Mph morphology plus cells of interdigitating appearance in T-cell areas, suggesting that these cells might belong to the Mph cell lineage. There was no reaction with other types of cells, such as Langerhans cells, osteoclasts, dendritic reticulum cells, and endothelial cells. The fact that the molecule recognised by mAb 24 is particularly associated with Mph in lymphoid tissue suggests that it might have a function in immune responses.     

Production of C3 as a marker of lymphokine-mediated macrophage activation

C3 production was assayed using an enzyme-linked immunosorbent assay (ELISA) in cell-free supernatants harvested from thioglycollate-elicited macrophages exposed to a variety of macrophage stimulating and activating agents. Macrophage monolayers treated with the stimulating agents starch, glycogen, and zymosan secreted three- to four-fold less C3 (mean 12 ng/10(5) cells/12 hr) than macrophages exposed to lymphokines containing macrophage-activating factor (MAF) (mean C3 production 44 ng/10(5) cells/12 hr). The increased production of C3 in macrophages exposed to MAF parallels the ability of these macrophages to acquire tumoricidal capacity as monitored in an in vitro 72 hr tumor cell cytotoxicity assay using B16 melanoma cells. Macrophages previously rendered tumoricidal by exposure to MAF and which are refractory to further challenge by MAF following decay of their tumoricidal properties, do not produce C3 on rechallenge with MAF. Exposure of refractory macrophages to liposome-encapsulated MAF overcomes the refractory state and induces re-expression of the tumoricidal phenotype and C3 production. We conclude that quantitative detection of macrophage-generated C3 antigen provides a useful biochemical marker for monitoring the acquisition of tumoricidal properties in macrophages exposed to MAF and offers a sensitive assay for screening novel agents that activate macrophages via mechanisms similar to MAF.     

The dynamics of cytostatic factor production by inactivated resident peritoneal macrophages from Syrian hamsters]

Results presented indicate that resident peritoneal macrophages (Mph) of intact, or tumor-bearing Syrian hamsters release cytostatic factor(s) (CSF) independently on the presence of serum in culture medium and the degree of Mph adherence. Dynamics of CSF secretion and accumulation depends on the number of Mph and duration of time of CSF production. It has been shown that at later time of Mph cultivation (24 hours) supernatants examined can stimulate proliferation of the target cells.     

Saccharomyces cerevisiae MPH1 gene, required for homologous recombination-mediated mutation avoidance, encodes a 3' to 5' DNA helicase

The MPH1 (mutator pHenotype 1) gene of Saccharomyces cerevisiae was identified on the basis of elevated spontaneous mutation rates of haploid cells deleted for this gene. Further studies showed that MPH1 functions to channel DNA lesions into an error-free DNA repair pathway. The Mph1 protein contains the seven conserved motifs of the superfamily 2 (SF2) family of nucleic acid unwinding enzymes. Genetic analyses have found epistasis of the mph1 deletion with mutations in the RAD52 gene group that mediates homologous recombination and DNA repair by homologous recombination. To begin dissecting the biochemical functions of the MPH1-encoded product, we have expressed it in yeast cells and purified it to near homogeneity. We show that Mph1 has a robust ATPase function that requires single-stranded DNA for activation. Consistent with its homology to members of the SF2 helicase family, we find a DNA helicase activity in Mph1. We present data to demonstrate that the Mph1 DNA helicase activity is fueled by ATP hydrolysis and has a 3' to 5' polarity with respect to the DNA strand on which this protein translocates. The DNA helicase activity of Mph1 is enhanced by the heterotrimeric single-stranded DNA binding protein replication protein A. These results, thus, establish Mph1 as an ATP-dependent DNA helicase, and the availability of purified Mph1 should facilitate efforts at deciphering the role of this protein in homologous recombination and mutation avoidance.     

Influenza virus A infection of human monocyte and macrophage subpopulations reveals increased susceptibility associated with cell differentiation

Influenza virus infection accounts for significant morbidity and mortality world-wide. Interactions of the virus with host cells, particularly those of the macrophage lineage, are thought to contribute to various pathological changes associated with poor patient outcome. Development of new strategies to treat disease therefore requires a detailed understanding of the impact of virus infection upon cellular responses. Here we report that human blood-derived monocytes could be readily infected with the H3N2 influenza virus A/Udorn/72 (Udorn), irrespective of their phenotype (CD14(++)/CD16(-), CD14(++)/CD16(+) or CD14(dim)CD16(++)), as determined by multi-colour flow cytometry for viral haemagglutinin (HA) expression and cell surface markers 8-16 hours post infection. Monocytes are relatively resistant to influenza-induced cell death early in infection, as approximately 20% of cells showed influenza-induced caspase-dependent apoptosis. Infection of monocytes with Udorn also induced the release of IL-6, IL-8, TNFα and IP-10, suggesting that NS1 protein of Udorn does not (effectively) inhibit this host defence response in human monocytes. Comparative analysis of human monocyte-derived macrophages (Mph) demonstrated greater susceptibility to human influenza virus than monocytes, with the majority of both pro-inflammatory Mph1 and anti-inflammatory/regulatory Mph2 cells expressing viral HA after infection with Udorn. Influenza infection of macrophages also induced cytokine and chemokine production. However, both Mph1 and Mph2 phenotypes released comparable amounts of TNFα, IL-12p40 and IP-10 after infection with H3N2, in marked contrast to differential responses to LPS-stimulation. In addition, we found that influenza virus infection augmented the capacity of poorly phagocytic Mph1 cells to phagocytose apoptotic cells by a mechanism that was independent of either IL-10 or the Mer receptor tyrosine kinase/Protein S pathway. In summary, our data reveal that influenza virus infection of human macrophages causes functional alterations that may impact on the process of resolution of inflammation, with implications for viral clearance and lung pathology.     

Biochemical studies of the Saccharomyces cerevisiae Mph1 helicase on junction-containing DNA structures

Saccharomyces cerevisiae Mph1 is a 3-5' DNA helicase, required for the maintenance of genome integrity. In order to understand the ATPase/helicase role of Mph1 in genome stability, we characterized its helicase activity with a variety of DNA substrates, focusing on its action on junction structures containing three or four DNA strands. Consistent with its 3' to 5' directionality, Mph1 displaced 3'-flap substrates in double-fixed or equilibrating flap substrates. Surprisingly, Mph1 displaced the 5'-flap strand more efficiently than the 3' flap strand from double-flap substrates, which is not expected for a 3-5' DNA helicase. For this to occur, Mph1 required a threshold size (>5 nt) of 5' single-stranded DNA flap. Based on the unique substrate requirements of Mph1 defined in this study, we propose that the helicase/ATPase activity of Mph1 play roles in converting multiple-stranded DNA structures into structures cleavable by processing enzymes such as Fen1. We also found that the helicase activity of Mph1 was used to cause structural alterations required for restoration of replication forks stalled due to damaged template. The helicase properties of Mph1 reported here could explain how it resolves D-loop structure, and are in keeping with a model proposed for the error-free damage avoidance pathway.     

A subpopulation of peritoneal macrophages form capillarylike lumens and branching patterns in vitro

OBJECTIVE: We have previously shown that monocytes/macrophages (MC/Mph) influence neovascularization by extracellular matrix degradation, and by direct incorporation into growing microvessels. To date, neither the phenotype of these cells, nor the stages of their capillary-like conversion were sufficiently characterized. METHODS: We isolated mouse peritoneal Mph from transgenic mice expressing fluorescent proteins either ubiquitously, or specifically in the myelocytic lineage. These Mph were embedded in Matrigel which contained fluorescent protease substrates, exposed to an MCP-1 chemotactic gradient, and then examined by confocal microscopy after various intervals. RESULTS: Within 3 hrs after gel embedding, we detected TIMP-1 and MMP-12 dependent proteolysis of the matrix surrounding Mph, mostly in the direction of high concentrations of MCP-1. After 2 days, Mph developed intracellular vacuoles containing degradation product. At 5 days these vacuoles were enlarged and/or fused to generate trans-cellular lumens in approximately 10% of cells or more (depending on animal's genetic background). At this stage, Mph became tubular, and occasionally organized in three-dimensional structures resembling branched microvessels. CONCLUSION: Isolated mouse peritoneal Mph penetrate Matrigel and form tunnels via a metalloprotease-driven proteolysis and phagocytosis. Following a morphological adjustment driven by occurrence, enlargement and/or fusion process of intracellular vacuoles, similar to that described in bona fide endothelium, a subpopulation of these cells end up by lining a capillary-like lumen in vitro. Thus we show that adult Mph, not only the more primitive 'endothelial progenitors', have functional properties until now considered defining of the endothelial phenotype.     

Mph1p promotes gross chromosomal rearrangement through partial inhibition of homologous recombination

Gross chromosomal rearrangement (GCR) is a type of genomic instability associated with many cancers. In yeast, multiple pathways cooperate to suppress GCR. In a screen for genes that promote GCR, we identified MPH1, which encodes a 3'-5' DNA helicase. Overexpression of Mph1p in yeast results in decreased efficiency of homologous recombination (HR) as well as delayed Rad51p recruitment to double-strand breaks (DSBs), which suggests that Mph1p promotes GCR by partially suppressing HR. A function for Mph1p in suppression of HR is further supported by the observation that deletion of both mph1 and srs2 synergistically sensitize cells to methyl methanesulfonate-induced DNA damage. The GCR-promoting activity of Mph1p appears to depend on its interaction with replication protein A (RPA). Consistent with this observation, excess Mph1p stabilizes RPA at DSBs. Furthermore, spontaneous RPA foci at DSBs are destabilized by the mph1Delta mutation. Therefore, Mph1p promotes GCR formation by partially suppressing HR, likely through its interaction with RPA.     

The hairpin region of Ndc80 is important for the kinetochore recruitment of Mph1/MPS1 in fission yeast

The establishment of proper kinetochore-microtubule attachments facilitates faithful chromosome segregation. Incorrect attachments activate the spindle assembly checkpoint (SAC), which blocks anaphase onset via recruitment of a cohort of SAC components (Mph1/MPS1, Mad1, Mad2, Mad3/BubR1, Bub1 and Bub3) to kinetochores. KNL1, a component of the outer kinetochore KMN network (KNL1/Mis12 complex/Ndc80 complex), acts as a platform for Bub1 and Bub3 localization upon its phosphorylation by Mph1/MPS1. The Ndc80 protein, a major microtubule-binding site, is critical for MPS1 localization to the kinetochores in mammalian cells. Here we characterized the newly isolated mutant ndc80-AK01 in fission yeast, which contains a single point mutation within the hairpin region. This hairpin connects the preceding calponin-homology domain with the coiled-coil region. ndc80-AK01 was hypersensitive to microtubule depolymerizing reagents with no apparent growth defects without drugs. Subsequent analyses indicated that ndc80-AK01 is defective in SAC signaling, as mutant cells proceeded into lethal cell division in the absence of microtubules. Under mitotic arrest conditions, all SAC components (Ark1/Aurora B, Mph1, Bub1, Bub3, Mad3, Mad2 and Mad1) did not localize to the kinetochore. Further genetic analyses indicated that the Ndc80 hairpin region might act as a platform for the kinetochore recruitment of Mph1, which is one of the most upstream SAC components in the hierarchy. Intriguingly, artificial tethering of Mph1 to the kinetochore fully restored checkpoint signaling in ndc80-AK01 cells, further substantiating the notion that Ndc80 is a kinetochore platform for Mph1. The hairpin region of Ndc80, therefore, plays a critical role in kinetochore recruitment of Mph1.     

Accessory cell function during monocyte/macrophage differentiation: relation to interleukin-1 (IL-1 beta) production and release

Human peripheral blood monocytes (Mo) can differentiate into highly active accessory cells and approach the phenotype and function of dendritic cells instead of developing into macrophages (Mph). Here we report that monocyte-derived accessory cells (m-AC), but not Mph, spontaneously synthesize and release high amounts of interleukin-1 (IL-1 beta). Furthermore, m-AC retained a high T-cell stimulatory activity and a non-macrophagic phenotype for at least 12 days in culture. They were shown to be weakly adherent, non-phagocytic, and most of them were negative for nonspecific esterase. In contrast, Mo differentiating into mature Mph only transiently showed an elevated accessory function but at no time appeared to release intracellular IL-1 beta into the supernatant when cultured in the absence of exogenous triggers. Additionally, they gained a high phagocytic capacity and a strong expression of Fc-receptors within 4 days. Addition of lipopolysaccharides (LPS) to Mph stimulated IL-1 beta release but concomitantly led to a strong reduction of the Mph-phenotype. Thus, the release of IL-1 beta from monocyte-derived cells negatively correlated with the expression of the Mph phenotype but did not necessarily correlate with their accessory function. These observations may reflect an antagonistic regulation of Mph phenotype and cytokine release in cells of the monocytic lineage and suggest that IL-1 beta release is not essential for accessory activity but might serve rather as an autocrine signal to prolong the accessory function of m-AC.     

The mph1 helicase can promote telomere uncapping and premature senescence in budding yeast

Double strand breaks (DSBs) can be repaired via either Non-Homologous End Joining (NHEJ) or Homology directed Repair (HR). Telomeres, which resemble DSBs, are refractory to repair events in order to prevent chromosome end fusions and genomic instability. In some rare instances telomeres engage in Break-Induced Replication (BIR), a type of HR, in order to maintain telomere length in the absence of the enzyme telomerase. Here we have investigated how the yeast helicase, Mph1, affects DNA repair at both DSBs and telomeres. We have found that overexpressed Mph1 strongly inhibits BIR at internal DSBs however allows it to proceed at telomeres. Furthermore, while overexpressed Mph1 potently inhibits NHEJ at telomeres it has no effect on NHEJ at DSBs within the chromosome. At telomeres Mph1 is able to promote telomere uncapping and the accumulation of ssDNA, which results in premature senescence in the absence of telomerase. We propose that Mph1 is able to direct repair towards HR (thereby inhibiting NHEJ) at telomeres by remodeling them into a nuclease-sensitive structure, which promotes the accumulation of a recombinogenic ssDNA intermediate. We thus put forward that Mph1 is a double-edge sword at the telomere, it prevents NHEJ, but promotes senescence in cells with dysfunctional telomeres by increasing the levels of ssDNA.     

利拉鲁肽下调游离脂肪酸作用下βTC3 细胞PERK 的表达

目的:探讨游离脂肪酸(FFA)作用下胰岛βTC3细胞双链RNA依赖性蛋白样内质网激酶(PERK)的表达以及利拉鲁肽(Lira)对其表达的干预作用。方法:以βTC3细胞为研究对象,分为对照组和FFA组(0.125,0.25,0.5及1 mmol/L)孵育24 h,Westernblot方法检测PERK的表达。然后,分为对照组,FFA组,和FFA+Lira组(0.5 mg/L和1 mg/L),Lira预孵育6 h后,1 mmol/L FFA继续孵育24 h,Western blot检测PERK的表达。结果:①不同浓度FFA孵育24 h后,与对照组相比,1 mmol/L FFA组PERK表达增加(P<0.05)。②与1 mmol/L FFA组相比,0.5mg/L Lira+1 mmol/L FFA和1 mg/L Lira+1 mmol/L FFA组PERK表达减少(P<0.05),两组之间有统计学差异(P<0.05)。结论:FFA作用能够上调βTC3细胞PERK的表达,而Lira在一定程度上逆转FFA水平异常导致的βTC3细胞PERK表达上调,减轻内质网应激反应。     

Characterization of the Growth Factor Activity of Amniotic Fluid on Cells from Hematopoietic and Lymphoid Organs of Different Life Stages

We investigated the proliferation-promoting effects of murine amniotic fluid (MAF) on in vitro cultured cells originally obtained from murine hematopoietic and lymphoid organs at different life stages. MAF promoted proliferation of the fetal liver cells (FLC), newborn spleen cells and adult bone marrow cells. The proliferation-promoting activity of MAF was extended to liver cells and spleen cells from mice younger than 2 weeks old. MAF did not, however, promote the proliferation of newborn or adult thymocytes, or of spleen cells, liver cells or peritoneal cells from 2-week-old or older mice. Rather, it partially inhibited the proliferation of spleen cells, thymocytes and peritoneal cells from 1-year-old mice. These results suggest that MAF contains growth factors for hematopoietic stem cells but not for either mature or immature T lymphocytes. Supporting this view, the MAF activity was partially neutralized by a polyclonal anti-mouse stem cell factor (SCF) antibody. Moreover, the immunoblotting of MAF against anti-mouse SCF antibody revealed a band at 30–32 kDa corresponding to the previously reported SCF. Interestingly, MAF was able to maintain FLC and adult bone marrow cells alive in culture for a relatively long time (2 weeks). The MAF activity was further shown to be partially and cell type-dependently antagonized by TNF-α and TGF-β. These results provided evidence that MAF contains potentially multiple growth factors preferentially affecting the early stage of hematopoiesis, one of which is SCF.     

Immunosuppressive properties of mouse amniotic fluid.

Previous reports have suggested that the alpha-fetoprotein present in mouse amniotic fluid is a potent nontoxic immunosuppressant. In the present studies mouse amniotic fluid (1:50) from 9- to 20-day gestations markedly inhibited the in vitro responses of mouse spleen cells to SRBC, and spleen cells from nonpregnant females were more affected than were cells from pregnant mice. On the other hand, MAF was less effective in depressing antigen- and mitogen-induced proliferation of human blood cells than were NMS or human serum. Human AF and cord sera did not significantly depress the immune responses of cells from mouse or man when added to cultures at concentrations sufficient to achieve levels of alpha-fetoprotein reported to be immunosuppressive if mouse AFP is used. While these studies do not identify the inhibitory agent(s) present in MAF, they do suggest that mouse AFP either is pharmacologically different from human AFP and/or that the immunosuppressive activity attributed to mouse AFP is actually produced by another agent physically associated with it.     

Production of specific macrophage activating factor by lymphocytes from tumor-bearing mice.

Lymphocytes from C57BL mice bearing a syngeneic UV-induced fibrosarcoma (UV-112) produced macrophage activating fatcor (MAF) when cultured with UV-112 cells in vitro. This MAF rendered normal C57BL macrophages cytotoxic in vitro to UV-112 cells. MAF production and lymphocyte-mediated cytotoxicity were detected in the early stages of tumor growth, but were absent in mice bearing large tumors. This eclipsed reatcivity was specific for the growing tumor. Lymphocytes from mice bearing a large UV-112 tumor were still able to produce MAF in response to B16 melanoma to which they had been preimmunized. In all instances, the MAF produced was specific in that it rendered syngeneic macrophages cytotoxic against only the tumor used for immunization.     

Identification of strains isolated as total and fecal coliforms and comparison of both groups as indicators of fecal pollution in tropical climates

This study was undertaken to better characterize the groups of total coliforms (TC) and fecal coliforms (FC) and to evaluate both groups as indicators of fecal contamination of drinking well water in a tropical climate (The Ivory Coast, West Africa). Isolated colonies obtained as TC or FC on membrane filters were identified using the API-20E system. From the well water samples, 58 golden-green colonies with a metallic sheen isolated on Endo medium (TC) were identified as Escherichia coli (55%), Enterobacter (26%), Klebsiella (14%), Proteus (3%), and Citrobacter (2%). Among 132 colonies isolated on Endo medium as non-TC (not showing the characteristic golden metallic sheen), 10% were identified as E. coli. The 196 blue colonies isolated on M-FC medium at 44.5 degrees C (FC) were identified as E. coli (66%), Klebsiella (12%), Enterobacter (10%), Citrobacter (5%), Salmonella (3%), Serratia (3%), Proteus (2%), and Yersinia (0.5%). Among 24 nonblue colonies on M-FC medium, none were identified as E. coli. Of the colonies isolated from human feces, E. coli represents 92% of the TC and 89% of the FC. Although these results are limited, they tend to confirm the greater specificity of the fecal coliform technique over that of total coliform for the detection of fecal contamination of untreated well water. From the results presented here and the observations of other workers, it is suggested that the use of FC instead of TC should be considered as the method of choice for determining drinking water pollution of untreated groundwater supplies.     

d-Mannose as a component of the macrophage surface receptor for macrophage-activating factor (MAF) in mice

Mouse peritoneal exudate macrophages were rendered cytostatic and cytolytic for various mouse tumor cells in vitro by exposure to partially purified lymphokines containing macrophage-activating factor (MAF) at 37 °C for 2 hr. The macrophage activation disappeared completely when either 0.1 Md-mannose or 0.1 M methyl-d-mannoside was present with MAF. On the other hand, neither d-galactose nor d-glucose inhibited the activation, and l-fucose, l-rhamnose, and N-acetyl-d-glucosamine inhibited it only partially. Incubation of either macrophages or MAF with 0.1 Md-mannose for 2 hr had no effect on activation of the macrophages by the MAF. Treatment of the macrophages by α-d-mannosidase rendered them no longer responsive to MAF. Macrophages treated by either neuraminidase or proteolytic enzymes, but not with β-d-galactosidase lost their ability to respond to MAF. Treatment of MAF with α-d-mannosidase did not affect MAF activity. In addition, MAF activity was not reduced by passage through a column of immobilized concanavalin A. In an absorption experiment, the presence of d-mannose was shown to prevent the adsorption of MAF to macrophages, while d-galactose did not. Treatment of macrophages with plant lectins having affinity for d-mannose, sialic acid or l-fucose prevented the adsorption of MAF, but the other lectins did not. Mouse MAF failed to adsorb to guinea pig peritoneal exudate macrophage, which were suggested as having a fucose-containing glycolipid as a lymphokine receptor. Taken together, these results strongly suggest that the receptor for MAF on mouse macrophages may be a glycoprotein containing d-mannose and sialic acid as essential components.     

Production of antitumor cytostatic factors by nonactivated resident macrophages of the peritoneal cavity of Syrian hamsters

The production of soluble cytostatic (CS) factor(s) by nonactivated peritoneal resident macrophages (Mph) of Syrian hamsters was found with the use of susceptible spontaneously transformed in vitro cells of STHE cell strain. The CS factor was determined by two modifications of CS test: 1) incorporation of 3H-TdR to the nuclei of target cells and 2) direct determination of the number of cells in the wells. The selected in vivo highly malignant variant of STHE strain appeared to be resistant to CS factors Mph.     

Budding yeast Mph1 promotes sister chromatid interactions by a mechanism involving strand invasion

Stalling of replication forks at lesions is a serious threat to genomic integrity and cell viability. Cells have developed a variety of pathways that allow continuation of synthesis, including translesion synthesis, postreplication repair and homologous recombination. We have devised a sensitive genetic system for detection of sister chromatid interactions in Saccharomyces cerevisiae. A 266bp sequence duplication in the KanMX4 module was generated and reversions were scored via G418 resistant colonies. Both 4-NQO induced and spontaneous reversions are strictly dependent on RAD52. Damage-induced reversions are also largely dependent on RAD51. Thus, most damage-induced events require a strand invasion step. Induced reversions were not affected in rev3 mutants and partially reduced in rad30 mutants indicating an involvement of Pol η. In cells lacking Mph1, a member of the FANCM family of DNA helicases, that has been implicated in a pathway for fork reactivation involving homologous recombination, damage-induced events are significantly reduced. Together with the spontaneous mutator phenotype of mph1 mutants this data strongly suggest that Mph1 has an additional function in recombination besides its previously described ability to disrupt D-loops. We propose that Mph1 promotes D-loop formation.     

IL-6 and IL-1 enhance the accessory activity of human blood monocytes during differentiation to macrophages

The role of IL-6 and IL-1 in the regulation of accessory activity and differentiation in the human monocyte/macrophage (Mo/Mph) system was investigated. IL-6 combined with IL-1 had a strong effect on the accessory activity of Mo-derived cells dependent on their state of differentiation in vitro. Fresh Mo prepared from peripheral blood differentiated into potent accessory cells in vitro within 24 h in the absence of exogenous triggers in serum-containing and serum-free medium. Mo cultured for 2 days in the presence of the cytokines IL-6 and IL-1 did not significantly increase their spontaneous accessory activity. However, the simultaneous addition of antibodies against IL-6 and IL-1 to accessory Mo cultures significantly diminished their T cell stimulatory capacity. These findings suggest an important positive feedback role of IL-6 and IL-1, secreted by Mo at this early state of differentiation. In marked contrast, untreated mature Mph generated in vitro from Mo exhibited a low spontaneous accessory potency. However, when these cells were subjected to IL-6 and/or IL-1, we observed a strong dose dependent increase in their potency to stimulate a T cell response. Parameters indicating the differentiation of Mo to Mph, such as acid phosphatase and 5' nucleotidase, were not influenced by the addition of IL-1, IL-6, or a mixture of both and confirmed the presence of mature Mph after 6 days of culture. Based on these observations, we conclude that the monocyte-derived cytokines IL-6 and IL-1 not only directly act on T cells but may also function as a signal for accessory activity during Mo/Mph differentiation.