Effects of retinoic acid and phorbol ester on lymphocytes and monocytes in B-lymphocytic leukemia

PBMC concentrated from 12 patients with CLL were incubated for up to 6 days with various doses of TPA or RA in an attempt to induce differentiation. The results show a great heterogeneity in the cellular response to both inducers. TPA produced two major changes in B-CLL cells, namely the development of some hairy-cell leukemia features with an increase in Ig secretion and the expression of Leu M5 and TAC receptors. In contrast to TPA, RA induced only modest or no changes in surface, but increased numbers of large macrophages were seen as assessed by latex-bead ingestion, expression of Fc receptors and cytochemistry. These changes were more obvious after exposure to RA than to TPA. Thus, while TPA induces mostly differentiation and hairy-cell features in B-lymphocytes, RA induces activation of the monocyte pool with no obvious changes in the lymphocytic compartment.

The effect of estradiol on human myelomonocytic cells. II. Mechanism of enhancing activity of colony formation

Elevated proportions of monocytes have previously been found in the blood of healthy women during the ovulation period as well as in other conditions associated with increased blood estradiol (E2). This phenomenon was explained, in part, by an augmenting effect which physiological concentrations of E2 may have on the development of granulocyte-macrophage (GM) colonies derived from normal peripheral blood mononuclear cells. To analyze this effect, we tested possible alternatives for the interaction between E2, colony-stimulating factor (CSF) and GM colony progenitor cells. E2 was found not to interact synergistically with CSF, but pre-treatment of the progenitor cells with E2 resulted in higher numbers of colonies in response to CSF. Moreover, E2 did not induce higher secretion of CSF but treatment with anti-CSF antibodies abolished the enhancing effect of E2. Based on these results, we suggest that the augmenting effect of E2 on GM colony formation is mediated by inducing the colony precursor cells to be more responsive to CSF. These findings may help to elucidate some of the complex relationships between estrogens, immune responses and hemopoiesis.

Interleukin 1 inhibitory activity secreted by a human myelomonocytic cell line (M20)

Culture supernatants from a myelomonocytic cell line (M20) were found to inhibit interleukin 1 (IL 1) activity in vitro. The factor, isolated from these supernatants, inhibited augmentation of phytohemagglutinin response of mouse thymus cells induced by IL 1 derived from several established cell lines. Various IL 1-dependent activities such as lymphocyte and fibroblast proliferation in vitro were also inhibited by the factor. The factor did not inhibit IL 2-induced or other proliferative responses not related to IL 1. Preliminary biochemical characterization of the factor indicated that the activity resides in a protein with a molecular mass of 52 kDa.

Detection of different interleukin-1 activities in human monocytes and monocytic cell lines

Culture supernatants from normal human monocytes, monocyte hybrid cell lines, and myelomonoblastic cell lines were tested for human interleukin-1 (IL-1) activity. In the present study, we report the detection of IL-1 secreted by several cell lines of monocyte origin and compare their biological and biochemical characteristics. IL-1 activity was tested by the regular assay of phytohemagglutinin (PHA) response of mouse thymus cells. IL-1 was found to be constitutively secreted by U937 and the M20 cell lines, as well as by three of the monocyte hybrid cell lines. The activity was always augmented following dialysis and did not require the presence of serum for its secretion. We compared the IL-1 activity of the myelomonoblastic M20 and hybrid 1C4 cell lines to that of normal monocytes. We found differences in the kinetics of IL-1 secretion, the pattern of activity following dilution of concentrated supernatants, and augmentation of activity by various inducers. The differences described may be explained by concomitant secretion of IL-1 inhibitory factors, as well as the secretion of activities other than IL-1. Preliminary biochemical analysis showed that all three cell sources tested shared some species of molecules characterized by gel filtration and ion-exchange chromatography. However, some species of molecules expressing IL-1 activity were unique to the cell lines and were not found in normal monocytes.

Parameters affecting the in vitro maturation of human monocytes to macrophages

In vitro maturation of human monocytes to macrophages was characterized by morphological criteria, cell size and lysosomal enzymes activity. Purified populations of monocytes were maintained in culture at either adherent or nonadherent conditions and their maturation to macrophages was observed in both cases. The addition of external factors such as hydrocortisone and vitamin D3 inhibited monocyte maturation. In the absence of external factors, nonadherent monocytes were inhibited in their maturation for up to 10 days when plated at crowded cell concentrations. In addition, the presence of human serum in the culture media had a higher inhibitory activity than similar concentrations of fetal calf serum. Supernates from crowded macrophages were also inhibitory for monocyte maturation. We suggest the possibility that cell crowding, as well as soluble factors found in the serum and probably secreted by macrophages, participate in the regulation of monocyte development by inhibiting their maturation. Once released from this inhibitory signal or environment, the monocytes mature to macrophages.

In vitro differentiation and establishment of cell lines derived from human myelomonocytic leukemia cells

Primary cultures of cells derived from 13 patients with acute myelomonocytic leukemia (AMML) were studied with particular emphasis on in vitro proliferation, cell differentiation and the mode for establishment of cell lines. Using irradiated human macrophage monolayers to assist cell growth, we obtained four new cell lines of myelomonocytic origin. All the cell lines were characterized for cytochemical markers and response to phorbol esters (TPA), a differentiation inducing agent. In the absence of any inducing agent, spontaneous differentiation of blast cells into mature macrophages-like cells occurred in 8 out of the 13 primary cultures. Thus, maturation induction by agents such as TPA is not always required in order to obtain leukemic cell differentiation in vitro. The regulation of cell proliferation and differentiation by cellular interactions and by extrinsic soluble products is discussed in detail, in the light of these findings.

The effect of estradiol on human myelomonocytic cells. 1. Enhancement of colony formation

Cyclic changes were observed in the content of blood monocytes during the menstrual cycle of normal women. Elevated blood monocytes were found during the ovulation period as well as in other conditions which are associated with increased blood estradiol (E2). To understand the possible association between E2 and monocytosis, we analysed the in vitro effect of E2 on the development of myelomonocytic colonies in culture. E2 in physiological concentrations was found to increase the number of colonies developed from peripheral blood mononuclear cells (PBM) of both females and males. The optimal concentration for the augmenting effect on males' PBM was lower than that for females. Mononuclear cells derived from cord blood, which yielded much higher numbers of colonies than adult PBM, also responded to the stimulatory effect of E2. Estrone and estriol were less effective than E2 in adult PBM. In contrast, progesterone, diethylstilbestrol and testosterone did not affect the number of colonies at the range of physiological concentrations tested. The anti-estrogen Tamoxifen did not inhibit the stimulatory effect of E2. The augmenting effect of E2 on monomyelocytic colony formation may explain at least in part the increase in blood monocyte content of women with high E2 as well as other phenomena of macrophage and granulocyte changes associated with the menstrual cycle.

A new myelomonoblastic cell line (M20): analysis of properties, differentiation, and comparison with other established lines of similar origin

A new myelomonoblastic cell line (M20) was established from the peripheral blood of a ten-year-old child with acute myeloblastic leukemia, using an improved method for supporting the initial stages of cell proliferation. The addition of irradiated macrophage monolayers to the proliferating cells appeared to overcome the deterioration of the primary cultures and enable them to continue proliferating until they became independent of this environment. The cell line that developed consisted of myeloblasts and promyelocytes characterized by light and scanning electron microscopy, cytochemistry, and enzymatic activities. The cells expressed Fc receptors and WT1 antigens but did not exhibit HLA-DR, HMA1, Epstein-Barr virus nuclear antigen, and surface Ig. The M20 cells produced colonies when cultured in semisolid medium and secreted lysozyme, prostaglandin E2, and interleukin 1. An attempt was also made to analyse the position of the M20 cells in the scheme of differentiation of the myelomonocytic lineage using different approaches. Treatment of the cells with 12-O-tetradecanoyl phorbol 13-acetate induced their adherence to plastic surfaces and partial maturation to macrophages as judged by morphological criteria, cytochemistry, and enzyme activities. However, comparison of the M20 cells to other well-established myelomonoblastic cell lines did not reveal any pattern suggesting a possible relationship between surface markers, cell function, and differentiation pathway of the various cell lines tested. Establishment of additional cell lines and identification of new markers may assist in defining the mechanisms involved in normal differentiation and malignant transformation of this cell lineage. In addition, such cell lines may also provide a tool for the quantitative recovery of a variety of monokines.

Establishment of cell lines from somatic cell hybrids between human monocytes and mouse myeloma cells

To study human monocyte functions, we attempted to immortalize human monocytes by producing somatic cell hybrids between such monocytes and the mouse myeloma cell line NSI. In this study we report the successful establishment of eight hybrid cell lines that have been grown in culture for more than a year, and some of them retained part of the human chromosome complement, as well as monocyte markers and activities. Karyotype analysis of these hybrid lines revealed that cells of seven out of eight of the lines contained one to 16 human chromosomes and in four of them, more than nine human chromosomes were observed. Several of the cell lines expressed monocytic markers and functions. Thus, in two of the hybrid lines nonspecific esterase could be demonstrated in 10 to 29% of the cells, and Fc receptors were demonstrated in three of the hybrid cell lines. Significant levels of human ferritin were detected in one of the lines, and two other cell lines secreted interleukin 1-like substance into the culture medium. These results encourage us to use human-mouse somatic cell hybridization as an approach for the establishment of human monocyte cell lines, which will preserve their functions and produce monocyte-derived factors.

Establishment of cell lines from somatic cell hybrids between human monocytes and mouse myeloma cells

To study human monocyte functions, we attempted to immortalize human monocytes by producing somatic cell hybrids between such monocytes and the mouse myeloma cell line NSI. In this study we report the successful establishment of eight hybrid cell lines that have been grown in culture for more than a year, and some of them retained part of the human chromosome complement, as well as monocyte markers and activities. Karyotype analysis of these hybrid lines revealed that cells of seven out of eight of the lines contained one to 16 human chromosomes and in four of them, more than nine human chromosomes were observed. Several of the cell lines expressed monocytic markers and functions. Thus, in two of the hybrid lines nonspecific esterase could be demonstrated in 10 to 29% of the cells, and Fc receptors were demonstrated in three of the hybrid cell lines. Significant levels of human ferritin were detected in one of the lines, and two other cell lines secreted interleukin 1-like substance into the culture medium. These results encourage us to use human-mouse somatic cell hybridization as an approach for the establishment of human monocyte cell lines, which will preserve their functions and produce monocyte-derived factors.

Selection and continuous growth of antigen-specific human T cells by antigen-treated monocytes

Antigen-specific human T lymphocytes were selected by adsorption of peripheral blood mononuclear cells on monolayers of antigen-treated autologous monocytes. The enriched cell populations were propagated in interleukin 2-containing medium for 60-80 days. Their activity was tested by a proliferative response against the sensitizing antigen in the presence of irradiated autologous lymphocytes. Continuous cultures of enriched T cells responded specifically to three different protein antigens. The specific reactivity induced in vitro against at least one of the antigens was probably a primary response. In addition, the selected cultures were found to be enriched for OKT4-positive cells, in contrast to cultures of nonselected T cells which were enriched for OKT8-positive cells. These properties of the selected T lymphocyte populations were obtained following only one exposure to the sensitizing antigen, which was concomitant with adsorbance on monocytes and without cloning of the reactive cells. We suggest that specific adsorbance of lymphocytes on antigen-treated monocytes may result in a T cell population which combines both properties of antigen specificity and enrichment for the helper proliferative subset of T cells.

Constitutive secretion of interleukin 1 by human monocytes

The constitutive and lipopolysaccharide (LPS)-induced secretion of interleukin 1 (IL 1) by cultured human monocytes and macrophages has been studied. Both freshly obtained monocytes and their culture-derived macrophages were induced by LPS to secrete similar amounts of IL 1. Such induction, however, was accompanied by the secretion of dialyzed inhibitory activity. Constitutive secretion of IL 1 was detected in concentrated supernatants of monocyte cultures. The factor obtained constitutively did not manifest significant inhibitory activity. A method is described for the recovery of IL 1-containing supernatants in serum- and other stimulant-free medium. The biological activities of the constitutively secreted IL 1 were similar to the LPS-induced activities. The constitutive secretion of IL 1 was not equally distributed in the entire monocyte population. We found that a small fraction of loosely adherent monocytes secreted higher amounts of IL 1 than the strongly adherent monocytes. However, the property of higher secretion of IL 1 was not stable and disappeared following monocyte cultivation. Thus, constitutive activity of IL 1 could be recovered either by concentrating the culture supernatants or by enriching a subset of monocytes with higher IL 1 activity.

Antigen presentation and regulatory functions of human monocytes in the in vitro response of lymphocytes against purified protein derivative of tuberculin (PPD)

Monocyte functions in the primary and secondary proliferative responses of human lymphocytes against purified protein derivative of tuberculin (PPD) have been studied. By applying the antigens either directly to the responding cells or on antigen-treated autologous monocytes, it was possible to distinguish between two different monocyte functions: antigen presentation and regulation. Their helper function in lymphocyte proliferation was found in cell-free supernatants of autologous and allogeneic monocytes and was expressed better in the secondary rather than in the primary responses. The antigen-presenting function of monocytes, however, was found to be more substantial in the primary response of lymphocytes. These results suggest that macrophage dependency of certain immune functions should be considered in regard to the various functions of macrophages, since at least quantitative differences for each of the macrophage functions were found in the primary and secondary proliferative responses.

Characterization of human lymphocytes which proliferate "spontaneously" in vitro

Human peripheral blood lymphocytes proliferate "spontaneously" in vitro following the reduction in the proportion of monocytes in culture. This cell proliferation, which takes place in the absence of any extrinsic antigenic stimulation, was found to reside in a small fraction of a non-T non-B cell population which was also Fc receptor-negative. Concomitant with the in vitro proliferation of the monocyte-depleted cells, an increase in the proportion of E rosette-forming cells was observed. Hence, in addition to the regulation of spontaneous proliferation of lymphocytes, it is suggested that monocytes may also be involved in the regulation of the proportion of T cells or in expression of the E-rosetting marker.

In vitro proliferation of macrophage depleted human peripheral blood lymphocytes

The incorporation of thymidine by normal human peripheral blood lymphocytes was tested in vitro following various culture conditions. A significant increase of thymidine uptake was observed in cultures depleted of plastic adherent, nylon wook adherent, or phagocytic cells. This proliferative activity occurred in the presence of various sera but was not due to a blastogenic response to a foreign protein, since it was also observed when autologous plasma was the only source of protein in the culture medium. The similarities and differences between this 'spontaneous' proliferative phenomenon and other blastogenic responses which are regulated by macrophages are discussed.