Cytofluorometric analysis of major histocompatibility antigens on human monocytes using monoclonal antibodies

Impaired antigen-presenting capability of monocytes correlated with their decreased expression of HLA-II antigens in patients with myeloid leukemia

Antigen-presenting capability and expression of HLA-II antigens on peripheral blood monocytes were analyzed by isotope incorporation technique and indirect immunofluorescence assay with monoclonal antibodies Tü 22, Tü 36 and anti-Leu-M2 in patients with acute and chronic myeloid leukemias (AML, CML). All patients (17 AML and 13 CML) demonstrated impaired antigen-presenting capability of monocytes (P < 0.001), when compared with simultaneously studied controls, which were HLA-identical normal siblings of the patients. These patients also showed a markedly decreased proportion of MAC-120- and HLA-DQ-positive monocytes as compared with the controls (P < 0.001), while the percentage of HLA-DR-positive monocytes in the patients was similar to that observed in the controls (P > 0.05). These findings suggested, therefore, that impaired antigen-presenting capability of monocytes correlated with their decreased expression of HLA-DQ in patients with acute and chronic myeloid leukemias.

Monoclonal antibodies to sheep MHC class II molecules recognize all HLA-D or subsets of HLA-D region products

Six murine monoclonal antibodies raised against sheep MHC class II molecules were analyzed for reactivity with HLA-D subregion products. All the antibodies reacted with human peripheral blood lymphocytes, monocytes, and B-lymphoblastoid cell lines homozygous for various HLA-DR specificities, suggesting that the antibodies recognized nonpolymorphic determinants on HLA class II molecules. SDS-PAGE and two-dimensional NEPHGE/SDS-PAGE analyses of molecules immunoprecipitated from 35S-methionine-labeled, DR-homozygous B-lymphoblastoid cell lines showed that the monoclonal antibodies precipitated typical class II molecules (Mr 32-34K and 25-29K). From comparison with antibodies of known HLA-D subregion specificity, two of the sheep antibodies appeared to react with the products of single HLA-D subregions, while another showed balanced reactivity with all HLA-D molecules. Antibody SBU.II 38-27 reacted exclusively with HLA-DQ molecules, antibody SBU.II 28-1 with HLA-DP molecules, and antibody SBU.II 49-1 with HLA-DR, -DQ, and -DP molecules. However, analysis of immunoprecipitates from surface-iodinated WT-49 cells (DR3 homozygous) using SBU.II 28-1 and the DP-specific monoclonal antibody B7/21, suggested that the two antibodies immunoprecipitated different alpha polypeptides. The two antibodies SBU.II 38-27 and 28-1 appear to be at least as specific as existing reagents, if not more so. As such, they are of value in their potential contribution to our understanding of the molecular characteristics and ultimately the functions of the HLA-DQ and -DP subregion products, as well as the identification/characterization of HLA-D equivalents in other species.

Electron microscopic study of HLA-DR and monocyte/macrophage staining cells in the rheumatoid synovial membrane

We examined synovial membrane samples from 6 rheumatoid arthritis (RA) and 3 osteoarthritis patients and from 1 normal subject, by an immunoelectron microscopic technique using anti-HLA-DR (anti-Ia) and anti-monocyte/macrophage (63D3) monoclonal antibodies. In the lining layer, the type A macrophage-like cells were strongly DR+ and 63D3+, whereas the type B fibroblast-like cells were almost completely negative. Lymphocyte-rich areas (containing more than 90% densely packed lymphocytes) showed weak and patchy DR staining of the lymphocytes. In these areas, 3-5% of the cells were macrophage-like cells which were 63D3-, a type of staining compatible with that of the interdigitating cell (IDC). In the plasma cell-containing (transitional) areas, many strongly DR+ macrophage-like cells were observed in close contact with lymphocytes and plasma cells. Ten to twenty percent of these cells were 63D3-, which suggests that they were IDC. Cells with the structural appearance of IDC were most frequently seen in those transitional areas which contained elevated concentrations (50-70%) of lymphocytes. In uninfiltrated interstitial areas, approximately 50% of the cells stained strongly with both anti-DR and 63D3 antibody, indicating that they were cells of monocyte/macrophage lineage, presumably histiocytes. This investigation has demonstrated the presence of the DR antigen in the RA synovial membrane on 1) phagocytic cells of the lining area, 2) lymphocytes and small numbers of IDC-like cells in dense, lymphocyte-rich areas, 3) large numbers of macrophage-like cells, of which some had the morphologic appearance of IDC, in transitional or plasma cell-containing areas, and 4) histiocytic cells in uninfiltrated interstitial areas. The observation of large numbers of DR+ macrophages and IDC-like cells in close contact with lymphocytes and plasma cells in the RA synovial membrane emphasizes their role in an active immune response. The observation of substantial numbers of potentially immunocompetent, DR+ histiocytic cells in uninfiltrated regions of the synovial membrane suggests that such cells may play a role in the progression of the synovial inflammatory reaction.

Assignment of determinants recognized by human alloantisera to HLA-D-subregion molecules by a lysostrip technique

We have used a lysostripping technique to investigate the molecular relationships of the determinants recognized by human alloantisera and murine monoclonal antibodies reactive with HLA-D region products. Cytotoxicity mediated by sera that define the specificities DR1, DR2, DR3, DR4, DR7, DRw11, DRw12, DRw13, DRw14, DRw52 and DRw53 was inhibited by anti-DR but not by anti-DQ Mabs. In contrast, sera that define DQw1, DQw2 and DQw3 were inhibited by anti-DQ but not anti-DR monoclonal antibodies. We found some sera used to define DR specificities that were not inhibited by monoclonal anti-DR. Cytotoxicity mediated by monoclonal antibodies reactive with the recently described specificities TA10 and MC1 was inhibited by anti-DQ and anti-DR monoclonal antibodies, respectively. The lysostripping technique is useful for the assignment of specific determinants to HLA-D subregion molecules.

Decreased expression of human class II antigens on monocytes from patients with acquired immune deficiency syndrome. Increased expression with interferon-gamma

The expression of HLA-DR (a class II histocompatibility antigen) on monocytes isolated from the peripheral blood of normal individuals and patients with acquired immune deficiency syndrome (AIDS) was investigated by the use of dual fluorescent staining and cytofluorometry. In animal models the absence of class II positive monocytes is linked to a failure of T cells to respond to antigens. We now report that patients with AIDS have a paucity of HLA-DR+ monocytes. The percentage of HLA-DR+ monocytes among eight normal individuals ranged from 49.3 to 95.0%+, and only one individual had less than 50% HLA-DR+ monocytes. HLA-DR expression on monocytes from homosexual male patients with lymphadenopathy was similar to that of normal subjects (range, 58.0 to 97.4%+). In contrast, seven of nine patients with AIDS had less than 50% HLA-DR+ monocytes (range, 13.4 to 78.8%+). The in vitro incubation of monocytes from AIDS patients with cloned human interferon-gamma resulted in an increase of the expression of HLA-DR to near normal levels.

Heterogeneity of human peripheral blood mononuclear cells detected by monoclonal antibodies to monomorphic determinants of human Ia antigens

The reactivity patterns of several monoclonal antibodies specific for monomorphic determinants of human Ia antigens were studied using flow cytometric techniques. We observed differential reactivity of these antibodies with human lymphoid cell lines, normal fresh human mononuclear cells, and lymphoblasts from PHA-activated cultures. The molecular heterogeneity of Ia antigens previously identified with immunochemical techniques was accompanied by heterogeneity of cell surface expression as identified by an immunofluorescent probe. The determinants identified by these anti-Ia monoclonal antibodies may provide useful markers in the isolation of cellular subpopulations responsive in the immune system.

Differential expression of Ia molecules by human monocytes

Human immune response genes can be divided into three distinct loci, each of which codes for three distinct families of Ia molecules: HLA-SB, HLA-DC, and HLA-DR. The tissue distribution and function of only one of these Ia molecules, HLA-DR, has been thoroughly studied. Using monoclonal antibodies, we examined the display of HLA-DR and HLA-DC molecules by adherent, human peripheral blood monocytes. The results of these studies demonstrate that although all human peripheral blood monocytes display easily detectable HLA-DR molecules, only 50% display easily detectable HLA-DC molecules. Separation of peripheral blood monocytes into HLA-DC+ and HLA-DC- cells demonstrates that each population displays an equivalent density of HLA-DR molecules. Therefore, on the basis of differences in their display of these two Ia molecules, adherent peripheral blood monocytes can be divided into two broad populations: HLA-DR+, HLA-DC+, and HLA-DR+, HLA-DC-. Despite the dis-coordinate display of these Ia antigens, the expression of both HLA-DR and HLA-DC can be regulated by a common signal, gamma interferon (IFN-gamma). Incubation of monocytes for 96 h in autologous serum leads to a marked decrease in the expression of both HLA-DR and HLA-DC. Addition of recombinant IFN-gamma to the cultures leads to reexpression of both HLA-DR and HLA-DC to levels comparable to those seen in fresh monocytes. In addition, although IFN-gamma does not modulate all monocyte surface markers, it can be demonstrated to modulate expression of one marker, MAC 120, in a manner similar to that observed for Ia antigens. These studies demonstrate that among human peripheral blood monocytes, the distribution of the Ia molecule, HLA-DC, is not coordinate with that of HLA-DR, although both respond to the same regulatory signal.

Pure interferon gamma enhances class II HLA antigens on human monocyte cell lines

Human recombinant interferon gamma (IFN-gamma) with a chemical purity of over 90% was shown to enhance membrane expression of HLA-DR antigens on cells from 3 human myelomonocytic lines (HL-60, U-937 and THP-1). Immunofluorescence techniques using a series of anti-HLA-DR monoclonal antibodies showed that the low, although variable, levels of DR-positive cells were clearly enhanced as soon as 24 h after incubation with IFN-gamma. Only IFN-gamma was able to exert this effect, since incubation with high concentrations of IFN-alpha or -beta did not induce any significant modification of the percentage of HLA-DR-positive cells. In contrast, doses of IFN-gamma as low as 2 units were effective, indicating a highly preferential, apparently selective effect of IFN-gamma for enhancement of HLA-DR expression. Private class II antigen expression was also enhanced by IFN-gamma on the U-937 cell line. Through its enhancing effect on class II public and private HLA antigens on the membrane of human monocytes, the IFN-gamma lymphokine may have a critical role in the modulation of antigen presentation by monocytes and on the regulation of HLA-DR-restricted cell cooperation.