A surface antigen marker for human monocytes

Membrane antigens of human cells of the monocyte/macrophage lineage studied with monoclonal antibodies

Three monoclonal antibodies, FMC17, FMC32, and FMC33 directed against human cells of the monocyte-macrophage lineage are described. The antibodies react strongly with blood monocytes and weakly, if at all, with granulocytes. Lymphoid cells are not stained. In tissue sections macrophages and interdigitating reticulum cells are stained. Lymphoid leukemia cells generally do not react with the antibodies, while myeloid leukemia cells give a variable pattern, with relatively differentiated cells more likely to react than undifferentiated cells. Differences between the 3 antibodies in their reactivity with leukemic cells and tissue macrophages indicate that they are directed against distinct antigens, which may serve as differentiation markers in the monocyte/macrophage lineage.

Small-scale isolation and characterisation of human peripheral blood monocytes

A technique is described for the isolation and characterisation of monocytes from 15 ml of human peripheral blood. After density gradient centrifugation over Ficoll-Hypaque, monocytes are purified further by substrate adherence under carefully defined conditions. The use of a simple microwell slide system permits the production of multiple small-scale monolayer populations which can be characterised further in terms of their histochemical reactivity (combined stain for chloroacetate and non-specific esterases); endocytic capacity (latex particles); Fc (sensitised ox erythrocytes) and C3 (serum-coated yeast) receptor expression; and precursor maturation potential (7-day cultures). Evidence of considerable cellular heterogeneity is presented.

HLA-A, -B, and -DR specificities on human monocytes

Monocyte-enriched cell suspensions obtained by a plate adherence method from 57 blood donors were typed by microcytotoxicity for HLA-A, -B and -DR determinants. Parallel assays were performed with autologous unfractionated lymphocytes for HLA-A and -B determinants and with autologous B-lymphocytes for HLA-DR determinants. Correlation coefficients (r values) were calculated for nine HLA-A specificities (r greater than 0.79), 16 HLA-B specificities (r greater than 0.56) and seven HLA-DR specificities (r greater than 0.81). For certain HLA-A and -B specificities detection was less readily achieved on monocytes than on autologous lymphocytes. Extra reactions were observed in some instances. With sera defining HLA-DR specificities, monocytes and B-cells showed reactivity of almost identical strength and reliability.

Monoclonal antibodies to human macrophage and leucocyte common antigens

Three monoclonal antibodies have been made to identify cells of the human mononuclear phagocyte system in fluids and tissues. The first, PHM 1, recognises a surface antigen common to all leucocytes. The other 2 antibodies, PHM 2 and PHM 3, bind to monocytes and macrophages but not to polymorphonuclear cells (PMN). PHM 2 labels all monocytes, macrophages and a small population of T-cells. PHM 3 labels most monocytes and macrophages but no other blood cells. The application of these monoclonal antibodies to the identification of mononuclear phagocytes in blood and liver using an unlabelled antibody immunoperoxidase (PAP) technique is demonstrated.

Ultrastructure and cytochemistry of human peripheral blood lymphocytes. Similarities between the cells of the third population and TG lymphocytes

The ultrastructural and cytochemical features of human peripheral blood TG cells (T cells with receptors IgG) and of the cells of the so-called third population (non-T, non-B cells with high avidity receptors for IgG) have been investigated and compared. Both TG and third-population cells (TPC) contained acid hydrolases with a paranuclear localization of alpha-naphthyl acid esterase, beta-glucuronidase or acid phosphatase. At the electron microscopy level, TG and TPC were indistinguishable and displayed rough cell surface, indented nuclei, abundant cytoplasm with predominance of the smooth over the rough membranes and peroxidase-negative granules. A large proportion of cells of the TPC could form rosettes with sheep erythrocytes after treatment with neuraminidase. The observed close similarities between TG and TPC may suggest that both cell types belong to a special subset of T cells. However, the alternative hypothesis that both TG and TPC are part of a subset unrelated to T cells, such as a new non-T, non-B cell population, or even of the monocytic-macrophage lineage, is also discussed.

Separation of human lymphocytes and monocytes by velocity sedimentation at unit gravity

An improved method of separating human peripheral blood lymphocytes and monocytes by velocity sedimentation at unit gravity is described. Cell separation capacity is considerably increased, while the time required for optimal separation is markedly reduced. Simple devices make it possible to layer and fractionate the gradients within 15 min. Overall recovery is 85%. On a small scale, monocytes were isolated greater than 80% pure from 4--20 X 10(7) mononuclear leukocytes. The average yield was 40% of all monocytes recovered after fractionation. In the same sedimentation runs 60% of all recovered lymphocytes were obtained strongly depleted of monocytes (monocyte contamination less than 0.2%). On a large scale 3--6 X 10(8) monocytes with an average purity of 85% were isolated from 3--6 X 10(9) mononuclear leukocytes in 2 subsequent runs. All cells recovered from the gradient were functionally active according to rosette formation, phagocytosis, stimulation by mitogens and in cytotoxicity tests.

Phenotypes of 'null' lymphoid cells in human blood

F(ab')2 antibody fragments of heteroantisera directed against p28,33 (or 'Ia-like') antigen, T-cell antigen(s) (T), myeloid antigen (M), and immunoglobulin have been used along with rosetting techniques to analyse the antigenic heterogeneity of 'null' or 'unclassified' lymphoid cells purified 'negatively' from human blood by E rosette depletion of T cells and B removal on an anti-immunoglobulin immunoabsorbent. The results confirm that considerable heterogeneity exists within the 'null' cell population; the majority of cells are p28,33+ and Fcgamma-receptor-positive, and a proportion but not all of these p28,33+, Fcgamma+ cells are also C3-receptor-positive but negative for the other heteroantigens (T and M). 2-6% were 'pre-B' by the criteria of immunofluorescent staining for cytoplasmic IgM in the absence of detectable cell surface Ig. 1-3% stained intensely with anti-IgM, anti-IgG or anti-IgA, or anti-k plus anti-lambda and were presumed to be plasma cells or their immediate precursors. No null cells stained with antibody to terminal deoxynucleotidyl transferase enzyme, a marker for early T lineage cells, and less than 1% expressed an acute ('non-T, non-B') lymphoblastic-leukaemia-associated membrane antigen which is believed to be an 'early' lymphoid lineage differentiation marker. A minor subpopulation made sheep 'E' rosettes, and another made mouse 'E' rosettes after neuraminidase pretreatment of the lymphoid cells. A small proportion of 'lymphoid', 'null cells' were reactive with an anti-myelomonocytic (M) antibody. It is suggested that 'null' lymphoid cells in blood are heterogeneous and that most are not immature T or B precursors but either a relatively mature B lymphocyte population with a very low density of membrane immunoglobulin or a distinct non-T, non-B cell type.

Lymphocyte subpopulations in man: no selective loss during isolation from defibrinated blood

Human lymphocytes isolated from defibrinated blood are characterized especially in relation to the total yield of lymphocytes and their subpopulations identified by membrane markers. The defibrination per se gives a significant loss of monocytes and granulocytes but no loss of lymphocytes, indicating that no selective loss of lymphocytes occurs. In a comparison of heparin-stabilized and defibrinated blood no difference in yield is found during every single step of the isolation procedure. Quantitation of E-RFC and SmIg-positive lymphocytes gives no differences in comparing the respective isolated suspensions of mononuclear cells. The observed difference in EA- and EAC-RFC can freely be ascribed to the difference in monocyte contamination. Further, no correlation is found between total lymphocyte yield and the relative number of the subpopulations identified, i.e. E-RFC, SmIg-positive, Fc-receptor- and complement-receptor-bearing lymphocytes. Hence it is concluded that defibrinated blood is optimal as blood source for the isolation of mononuclear cells when lymphocyte subpopulations are studied and enumerated.

Serological characterization of human monocytes for HLA, B-lymphocyte, granulocyte, and monocyte-associated antigens by cytotoxicity testing

Highly enriched preparations of monocytes, B and T lymphocytes, and granulocytes from 18 normal donors were serotyped in parallel in a complement-dependent cytotoxicity assay using allogeneic and heterologous antisera defining three independent tissue antigen systems. HLA and B-lymphocyte tissue antigens were detected on human monocytes although granulocyte antigens were absent. By cytotoxicity testing the presence of Ia-like antigens on monocytes was significantly diminished compared to the autologous B-lymphocyte population and has important implications in B-lymphocyte serology. The study indentified a number of human antisera obtained from multitransfused subjects and pre- and post-transplant organ recipients that were non-HLA and appeared to define monocyte-associated antigens. The serological implications of surface antigen expression on human monocytes compared with other peripheral blood cells are discussed.

Maturation linked expression of a myeloid cell surface antigen

An antiserum raised against myelomonocytic and monocytic leukaemia cells has been used to define a cell surface antigen shared by normal and leukaemic cells of the granulocyte and monocyte cell lines. The quantitative expression of this antigen was investigated using the Fluorescence Activated Cell Sorter and was shown to correlate with the degree of morphological maturation.

Two-step separation of human peripheral blood monocytes on discontinuous density gradients of colloidal silica-polyvinylpyrrolidinone

Normal human peripheral blood monocytes were purified by a two-step separation. The first step, the standard Ficoll--Hypaque (F--H) buoyant density centrifugation, yielded mainly mononuclear cells, of which 24 +/- 9% were monocytes. Isopycnic centrifugation on discontinuous gradients of colloidal silica polyvinylpyrrolidinone (CS-PVP) further separated these mononuclear cells. The density interface between 1.070 and 1.060 g/ml yielded 82 +/- 7% monocytes, 5 +/- 4% granulocytes and 13 +/- 8% lymphocytes. Sixty-six percent of the monocytes obtained after F--H separation were recovered in this layer. The monocytes were intact and viable and retained their ability to phagocytose and kill Candida pseudotropicalis and to spread on glass coverslips. Motility (both random and towards a chemoattractant) was retained but was quantitatively less than after F--H separation alone. The relative purity of the monocyte population allowed assessment of major histocompatibility surface antigens by serotyping. This confirmed the presence of HLA and Ia-like antigens on monocytes.

Acid esterase in human lymphoid cells and leukaemic blasts: a marker for T lymphocytes

A non-specific acid alpha-naphthyl-acetate esterase activity was investigated in human lymphoid cell populations from tonsils, blood, thymus and in different leukaemias. Four patterns have emerged. (i) The vast majority of T lymphocytes (peripheral blood, tonsils) showed a localized, intense reaction product ("T-like"). (ii) A thymocyte subpopulation expressed faint, localized enzyme activity ("Thy-like) but the majority of thymocytes showed no esterase activity. Some cells from acute lymphoblastic leukaemias with thymocyte surface characteristics had a "Thy-like" appearance. (iii) Most B lymphocytes and cells from chronic lymphocytic leukaemias were esterase negative. No activity was seen in mitogen activated peripheral blood T and B lymphoblasts from peripheral blood and in leukaemic blasts from the common form of childhood acute "lymphoblastic" leukaemia. (iv) Myeloid cells, including peripheral blood monocytes, and blast cells from acute myeloblastic and chronic granulocytic leukaemias showed an intense, diffuse reaction product (M-like). It is concluded that the modified esterase technique is a convenient marker for small mature human T lymphocytes in tissue sections and smears. It may also be helpful in the differential diagnosis of acute lymphoblastic leukaemia with T characteristics, the common form of acute "lymphoblastic" leukaemia and acute myeloblastic leukaemia.

Monocyte-reactive antibodies in patients with systemic lupus erythematosus

Cold-reactive antibodies cytotoxic for peripheral monocytes from more than half of normal donors were found in the sera of 2 of 25 patients with systemic lupus erythematosus (SLE) and 1 of 26 with rheumatoid arthritis (RA), and they were absent in 25 normal sera. In contrast, lymphocytotoxic activity for T or B lymphocytes was found in over half of the lupus sera. The antibodies to monocytes were primarily IgM and exhibited varying specificities. Some of the antibodies were directed against antigenic determinants common to monocytes, T and B cells, or against determinants shared between monocytes and one lymphocyte type. One serum possessed a high titer of antibodies that were specific for monocytes. The clinical significance of antimonocyte antibodies remains to be established.

T-cell regulation of immunoglobulin synthesis and proliferation in pokeweed (Pa-1)-stimulated human lymphocyte cultures

In pokeweed (Pa-1)-stimulated human lymphocyte cultures, T cells are essential for the survival, proliferation, plasma-cell development, and high-rate Ig secretion of B cells. Their effects are T-cell-specific in the sense that B-cell stimulation does not take place in the absence of T cells even when fibroblasts or monocytes are provided. The experimental system is the most effective model for activation of human B lymphocytes so far described. Plasmablast development requires approximately 7 days in culture. In T + B-cell cultures established at 1 X 10(6)/ml (1 X 10(4)/mm2) initial cell density, plasma cells can secrete, on the average, as much as 40-70 pg IgM or IgG per cell per day. When the initial T-cell density is increased well above 1.0 X 10(6)/ml, a T-cell-mediated depression of Ig synthesis becomes predominant. Thus, in the pokeweed model T-cell effects represent a balance of helper and suppressor influences. The study also shows that B cells are heterogeneous. A non-adherent IgG-committed (smIg-?) TONSIL B-cell population seems to be less susceptible to T suppressor effects than normal tonsil B cells. This subset proliferates particularly well and synthesizes large quantities of IgG in the presence of large initial proportions of T cells.

Identification of human mononuclear cells by anti-monocyte serum

An antiserum to human leukaemic monocytes was raised in rabbits. Adsorption with human thymocytes and chronic lymphatic leukaemia cells rendered the antiserum specific for cells of the human myeloid and monocytic cell series. Additional adsorption with granulocytes left a weak, but specific, activity for monocytes. The cells in normal peripheral blood with which the antiserum reacts by an immunoperoxidase technique have typical monocyte morphology. Cells with typical lymphocyte morphology do not react with the antiserum, but a few cells with intermediate morphology were also stained by the antiserum. Using the antiserum as a marker, the precursor cells of the monocytic and myeloid cell series were traced in the bone marrow.

Detection of monocyte specific antigen on human acute leukaemia cells

Heteroantisera with specificity for human monocyte and macrophage antigens (HuMa) have been tested for activity against peripheral blood cells from patients with acute leukaemia. Using indirect immunofluorescence, blast cells from 25/27 patients with acute myelomonocytic leukaemia were reactive with anti-HuMa antisera, whereas blasts from 19/20 patients with acute myeloblastic leukaemia and 13/13 patients with acute lymphoblastic leukaemia were not reactive. The F(ab1)2 fragment of the antibody retained specific activity. Activity of whole serum against myelomonocytic blast cells was specifically removed by absorption with macrophages. These observations indicate that circulating blast cells from patients with acute myelomonocytic leukaemia may carry differentiation antigens characteristic of monocytes and macrophages.

Identification of cells with monocyte markers in panhypogammaglobulinaemia

Nonphagocytic cells bearing receptors for complement and IgGFc in blood samples from four boys with panhypogammaglobulinaemia who lacked B lymphocytes were positively stained for human macrophage antigen (HuMA) and intracellular peroxidase. Similar non-T, non-B cells were found in adult blood preparations but in lower numbers than in the four boys above and in two of three other boys with various immunodeficiencies. Because of their monocyte characteristics, it is improbable that these cells are B-lymphocyte precursors; this is consistent with our view that there is a central failure of B-cell induction in boys with panhypogammaglobulinaemia who lack lymphocytes with surface immunoglobulin.