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REDUCTION OF PHAGOCYTOSIS AND LYSOSOMAL ENZYME RELEASE FROM HUMAN LEUKOCYTES BY SERUM FROM PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS ROBERT B. ZURIER Serums from 22 of 30 (73.3%)patients with systemic lupus erythematosus (SLE) interfered significantly with particle (zymosan) uptake and subsequent release from normal human neutrophils of lysosomal enzymes. SLE serums with low as well as those with normal functional hemolytic complement activity (CH50) suppressed phagocytosis and enzyme release despite the presence of normal serum in cell suspensions. The defect did not appear to be caused by anticomplementary activity of serum. Serums from patients whose clinical activity of disease varied from none to severe and whose treatment varied from none to high doses of prednisone were capable of suppressing phagocytosis and enzyme release. The severity of clinical SLE activity did not affect the degree of suppression. Serums from patients treated with corticosteroids were more inhibitory than serums from patients not so treated. The nature of the inhibitor is unknown. Phagocytic cells become the center of inflammatory lesions (1) partly because of release of substances previously sequestered within lysosomes. During uptake of particles such as zymosan and immune comFrom the Department of Medicine, University of Connecticut School of Medicine, Farmington, Connecticut 06032. Investigation supported by a grant from the University of Connecticut Research Foundation, U.S.P.H.S. Grant AM-17309, and a Clinical Grant from The Arthritis Foundation. Robert B. Zurier, M.D.: Assistant Professor of Medicine, Division of Rheumatic Diseases, Department of Medicine, University of Connecticut School of Medicine. Submitted for publication December 12, 1974; accepted May 19, 1975. Address reprint requests t o Dr. Zurier. Arthritis and Rheumatism, Vol. 19, No. 1 (January-February 1976)
plexes, polymorphonuclear leukocytes (PMN) of human blood remain viable and selectively extrude lysosomal, but not cytoplasmic enzymes (2-4). Systemic lupus erythematosus (SLE) is a disease characterized by immunoglobulin deposition and inflammation in several organs (5). It is not clear whether these deposits are ingested and/or degraded by phagocytic cells. Uptake and “processing” of antigen by phagocytic cells appear necessary for lymphocytes t o respond to antigen (6). Thus defects in cell-mediated immunity which have been demonstrated in patients with SLE (7-9) may be due in part to defects in phagocytosis. Although leukocytes from patients with SLE exhibit impaired phagocytic activity (lo), other factors have been implicated to explain the decrease in this cellular function. For example a decrease in IgM antibody titers to bacterial antigens (1 l), leukopenia (12), and low levels in serum of critical complement components (13,14) might account for impaired phagocytosis. In addition the phagocytic activity of peripheral blood monocytes is reduced when these cells are cultured in serum from patients with SLE (15). The results of this investigation suggest that there is present in serum from a substantial proportion of patients with SLE a factor or factors that interfere with particle uptake and subsequent release from PMN of lysosomal enzymes.
MATERIALS AND METHODS Human peripheral blood leukocytes obtained from normal donors were separated and suspended (4 X 106 cells/
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Serum Dilution Studies. Increments of SLE serum known to reduce particle uptake and enzyme release were added to cell suspensions that contained autologous serum (13.3% v/v). SLE serum was tested neat (without autologous serum) and a t final dilutions of 1:1, 1:2, 1:4, and 1:8. Anticomplementary activity was assayed in serums obtained from blood clotted at room temperature for I hour and stored at -70°C. Hemolytic complement activity (CHSO) wa: performed by the method of Mayer (21) before incubation 01 serum at 37°C for 60 minutes. Serum complement C 3 was determined on fresh serum or samples stored at 4°C using radial immunodiffusion (22) (immunoplate human complement C 3 test, Hyland Division, Travenol Laboratories, Inc, Costa Mesa, California). Anti-DNA Antibody. Antibodies to DNA were determined using a modified Farr technique and radiolabeled E coli (23).
ml) as previously described (2). Leukocyte suspensions contained approximately 85% PMN. The remaining cells were identified as monocytes and lymphocytes. Portions of cell suspensions (1 .O ml) were dispensed into 10 X 75 mm tubes. Cells were suspended in a medium (pH 7.4) of 10 mM phosphatebuffered saline to which calcium and magnesium had been added at final concentrations of 0.6 and 1 mM respectively. Cell suspensions were incubated at 37°C for 30 minutes in autologous or homologous or SLE serum (13.3% v/v), then exposed to zymosan for 30 minutes. Throughout the 60-minute incubation, tubes were turned by hand every 10 minutes. At the end of experiments, tubes were centrifuged at 755 g at 4°C for 2 minutes. The cell-free supernatants were removed for enzyme determination. The lysosomal marker P-glucuronidase was determined as previously described (16). Release of cytoplasmic lactate dehydrogenase (LDH) was used as an indicator of cell death. L D H was determined by the method of Wacker et a1 (17). Appropriate control experiments performed as previously described (2) confirmed that SLE serums did not inhibit activity of P-glucuronidase or LDH. Wright-stained preparations were made of cell pellet suspensions, and the average number of yeast particles ingested per P M N was estimated by light microscopy (18). The diagnosis of SLE in all patients studied was based on the criteria set forth by the American Rheumatism Association (19). Clinical activity of SLE was assessed according to the guidelines of Rothfield and Pace (20) on the basis of history and physical findings: Grade 0 (remission)-no clinical evidence of disease activity; Grade I-active disease in one system only; Grade 2-active disease in more than one system without fever, or in one system with fever; Grade 3-active disease in two or more systems with fever. The presence of either hematologic abnormalities (white blood count
REDUCTION OF PHAGOCYTOSIS AND LYSOSOMAL ENZYME RELEASE FROM HUMAN LEUKOCYTES BY SERUM FROM PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS ROBERT B. ZURIER Serums from 22 of 30 (73.3%)patients with systemic lupus erythematosus (SLE) interfered significantly with particle (zymosan) uptake and subsequent release from normal human neutrophils of lysosomal enzymes. SLE serums with low as well as those with normal functional hemolytic complement activity (CH50) suppressed phagocytosis and enzyme release despite the presence of normal serum in cell suspensions. The defect did not appear to be caused by anticomplementary activity of serum. Serums from patients whose clinical activity of disease varied from none to severe and whose treatment varied from none to high doses of prednisone were capable of suppressing phagocytosis and enzyme release. The severity of clinical SLE activity did not affect the degree of suppression. Serums from patients treated with corticosteroids were more inhibitory than serums from patients not so treated. The nature of the inhibitor is unknown. Phagocytic cells become the center of inflammatory lesions (1) partly because of release of substances previously sequestered within lysosomes. During uptake of particles such as zymosan and immune comFrom the Department of Medicine, University of Connecticut School of Medicine, Farmington, Connecticut 06032. Investigation supported by a grant from the University of Connecticut Research Foundation, U.S.P.H.S. Grant AM-17309, and a Clinical Grant from The Arthritis Foundation. Robert B. Zurier, M.D.: Assistant Professor of Medicine, Division of Rheumatic Diseases, Department of Medicine, University of Connecticut School of Medicine. Submitted for publication December 12, 1974; accepted May 19, 1975. Address reprint requests t o Dr. Zurier. Arthritis and Rheumatism, Vol. 19, No. 1 (January-February 1976)
plexes, polymorphonuclear leukocytes (PMN) of human blood remain viable and selectively extrude lysosomal, but not cytoplasmic enzymes (2-4). Systemic lupus erythematosus (SLE) is a disease characterized by immunoglobulin deposition and inflammation in several organs (5). It is not clear whether these deposits are ingested and/or degraded by phagocytic cells. Uptake and “processing” of antigen by phagocytic cells appear necessary for lymphocytes t o respond to antigen (6). Thus defects in cell-mediated immunity which have been demonstrated in patients with SLE (7-9) may be due in part to defects in phagocytosis. Although leukocytes from patients with SLE exhibit impaired phagocytic activity (lo), other factors have been implicated to explain the decrease in this cellular function. For example a decrease in IgM antibody titers to bacterial antigens (1 l), leukopenia (12), and low levels in serum of critical complement components (13,14) might account for impaired phagocytosis. In addition the phagocytic activity of peripheral blood monocytes is reduced when these cells are cultured in serum from patients with SLE (15). The results of this investigation suggest that there is present in serum from a substantial proportion of patients with SLE a factor or factors that interfere with particle uptake and subsequent release from PMN of lysosomal enzymes.
MATERIALS AND METHODS Human peripheral blood leukocytes obtained from normal donors were separated and suspended (4 X 106 cells/
ZURIER
74
Serum Dilution Studies. Increments of SLE serum known to reduce particle uptake and enzyme release were added to cell suspensions that contained autologous serum (13.3% v/v). SLE serum was tested neat (without autologous serum) and a t final dilutions of 1:1, 1:2, 1:4, and 1:8. Anticomplementary activity was assayed in serums obtained from blood clotted at room temperature for I hour and stored at -70°C. Hemolytic complement activity (CHSO) wa: performed by the method of Mayer (21) before incubation 01 serum at 37°C for 60 minutes. Serum complement C 3 was determined on fresh serum or samples stored at 4°C using radial immunodiffusion (22) (immunoplate human complement C 3 test, Hyland Division, Travenol Laboratories, Inc, Costa Mesa, California). Anti-DNA Antibody. Antibodies to DNA were determined using a modified Farr technique and radiolabeled E coli (23).
ml) as previously described (2). Leukocyte suspensions contained approximately 85% PMN. The remaining cells were identified as monocytes and lymphocytes. Portions of cell suspensions (1 .O ml) were dispensed into 10 X 75 mm tubes. Cells were suspended in a medium (pH 7.4) of 10 mM phosphatebuffered saline to which calcium and magnesium had been added at final concentrations of 0.6 and 1 mM respectively. Cell suspensions were incubated at 37°C for 30 minutes in autologous or homologous or SLE serum (13.3% v/v), then exposed to zymosan for 30 minutes. Throughout the 60-minute incubation, tubes were turned by hand every 10 minutes. At the end of experiments, tubes were centrifuged at 755 g at 4°C for 2 minutes. The cell-free supernatants were removed for enzyme determination. The lysosomal marker P-glucuronidase was determined as previously described (16). Release of cytoplasmic lactate dehydrogenase (LDH) was used as an indicator of cell death. L D H was determined by the method of Wacker et a1 (17). Appropriate control experiments performed as previously described (2) confirmed that SLE serums did not inhibit activity of P-glucuronidase or LDH. Wright-stained preparations were made of cell pellet suspensions, and the average number of yeast particles ingested per P M N was estimated by light microscopy (18). The diagnosis of SLE in all patients studied was based on the criteria set forth by the American Rheumatism Association (19). Clinical activity of SLE was assessed according to the guidelines of Rothfield and Pace (20) on the basis of history and physical findings: Grade 0 (remission)-no clinical evidence of disease activity; Grade I-active disease in one system only; Grade 2-active disease in more than one system without fever, or in one system with fever; Grade 3-active disease in two or more systems with fever. The presence of either hematologic abnormalities (white blood count
