Inhibition of human serum complement activity by diisopropylfluorophosphate and selected anticholinesterase insecticides.

Activation of the human complement (C') system, a major line of defense against infections, requires the participation of serine esterases. Since the widely used anticholinesterase insecticides inhibit serine esterases, the present study evaluated potencies of carbaryl, carbofuran, dichlorvos, and paraoxon to inhibit C' activities of a panel of normal human sera. C'-mediated lysis of sheep red cells was measured with a modified assay (1) incorporating suboptimal concentrations of sensitizing antibody and (2) exhibiting increased sensitivity to serine esterase inhibitors. Test chemicals were added to diluted sera 2 hr prior to incorporation into C' reaction mixtures. Potencies to inhibit C' and serum cholinesterase (CHE) were compared to potencies of diisopropylfluorophosphate (DFP), a potent serine esterase inhibitor and a standard probe for C' esterases. At 0.5 to 3.0 mM, carbaryl, carbofuran, dichlorvos, and DFP produced a dose-dependent inhibition of lysis, whereas paraoxon was not inhibitory. On a molar basis, carbaryl was three times more potent than DFP, and inhibited lysis 15-25 and 26-45% at 1.0 and 3.0 mM, respectively. Carbofuran, dichlorvos, and DFP were equipotent. Mean IC50's for inhibition of CHE (a marker for occupational exposure to organophosphates and carbamates) by DFP, paraoxon, dichlorvos, carbofuran, and carbaryl were 1.0 X 10(-8), 4.1 X 10(-8), 1.0 X 10(-7), 3.3 X 10(-6), and 1.8 X 10(-5) M, respectively. Potencies of the insecticides to inhibit CHE did not predict absolute or relative potencies to inhibit serum C' activity.

Immunoglobulins and complement components in 37 patients infected by HIV-1 virus: comparison of general (systemic) and intrathecal immunity.

Intrathecal (IT) immunity was assessed by simultaneous analysis of paired cerebrospinal fluid (CSF) and sera of 37 patients infected by human immunodeficiency virus-1 (HIV-1). Only 8 of these 37 patients had no neurological or neuropsychiatric symptoms. There were 3 prominent abnormalities observed: (1) IT IgA production occurred in 15 patients, IT IgM production in 14 patients, and IT IgG production in 34 patients. (2) IT Anti-HIV-1 antibody specific activity (ASA) was higher than in serum in 33 of the 37 patients indicating that IT synthesis of antibody specific for HIV-1 occurs even in asymptomatic patients; IT anti-HIV-1 antibody synthesis was not correlated with clinical severity or neurological involvement. IT anti-herpes simplex ASA was also higher than serum ASA in 6 patients indicating a possible associated herpes simplex virus infection. (3) IT production of the complement component C4 was found frequently and was highly correlated with increased serum C4. IT C3 levels were decreased in 21 of 37 patients indicating that complement activation is a frequent accompaniment of the IT immune response in HIV-1-positive patients. These results indicate a unique and localized IT immune response which is different from the pattern observed in the systemic immune compartment in HIV-1-seropositive individuals and from the pattern common to the other CNS infectious diseases.

Evaluation of some immunologic indices in children with HBV-mediated membranous glomerulonephritis.

Evaluation of the selected parameters of the immune system in MGN children has revealed some correlation between clinical advancement of the disease and the presence of the immune complexes in the serum. The results obtained point to the predominance of the suppressive reaction.

Hypocomplementemia and human immunodeficiency virus infection. Clinical correlates and relationships to circulating immune complex and immunoglobulin G levels.

The levels of C4 and C3 were measured and related to other immunological and clinical parameters in 44 patients with the human immunodeficiency virus (HIV) infection. Circulating immune complexes (C1q-CIC) as measured by an enzyme-linked immunosorbent assay employing monoclonal antibody with specificity for bound Clq, and serum immunoglobulin G (IgG) concentrations were assessed simultaneously. Clinical parameters assessed included: (1) the presence of specific anti-infective medications; (2) the presence of hypotension and fluid administration, and (3) bacterial and specific opportunistic infections. Hypocomplementemia was observed in 25 of 46 sera for C3, and in 8 of 46 sera for C4. Clq-CIC increases were seen in 26 of 46 sera and hyper-IgG was present in 25 of 46 sera. Lower C3 concentrations were significantly associated with elevated Clq-CIC levels (p less than 0.001). There were significant correlations between Clq-CIC levels and C3 concentrations (p = 0.0065, negative) and IgG levels (p = 0.0075, positive). Clq-CIC were significantly higher with serum p-24 antigen levels of 50 pg/ml or greater. These data demonstrate that elevated Clq-CIC and hypocomplementemia are both common in HIV-infected patients and may have significant relationships.

Serum and CSF humoral immunity in Guillain-Barré syndrome: clinical correlations.

Paired samples of CSF and serum obtained from 29 patients affected with Guillain-Barré syndrome (GBS) were analyzed for various protein levels, including immunoglobulins and complement components. An attempt was made to correlate these findings to the clinical stage, severity, and duration of the disease. Intrathecal IgG synthesis was detected and quantified by means of a previously reported formula. It is practically constant in the GBS during the stage of stabilized paralysis, and is significantly greater in this stage than in the stage of progressive paralysis. Moreover, it increases with severity and duration (longer than 3 months) of the disease. Evidence of intrathecal C3 consumption is also presented.

A natural auto-inhibitory factor of the terminal complement pathway in serum of Ctenodactylus gondi.

The serum of Ctenodactylus gondi, a Tunisian rodent, contains a unique inhibitor of the terminal complement pathway. The auto-inhibitor has been partially characterized as a heat-stable euglobulin that is slightly retarded on a DEAE-ion exchange column at pH 7 and elutes as a symmetrical peak on Sephacryl S-300 in the mol. wt region of approximately 200,000. The inhibitor acts by preventing attachment of cytolytic C5b-9 complexes to natural target cells. It does not appear to affect formation and function of C3-convertase, does not exert inhibitory effects at stages later than C5b-7 formation, and also does not prevent formation of SC5b-9 in serum. That the factor prevents attachment of C5b-7/C5b-9 to cells has been demonstrated in hemolysis model systems using sheep EA + human serum, and in the C3-independent reactive lysis system with the use of ELISA methods and quantitative assays with radioiodinated C8. Addition of partially purified inhibitory factor to human sera or to sera of other animal species abolishes the hemolytic activities of these sera. The inhibitory factor of Gondi serum is the first inhibitor of the terminal pathway which has been shown to be capable of preventing cytolysis of cells undergoing complement attack under physiological conditions. The presence of this factor is probably partially responsible for the remarkable susceptibility of C. gondi towards bacterial and parasitic infections.

Nephrotic syndrome associated with varicella infection.

A 4-year-old boy developed nephrotic syndrome following varicella infection. Serologic studies during the early phase of the disease demonstrated a decrease in serum C3, C4, and properdin factor B. Renal biopsy revealed an acute proliferative glomerulonephritis with deposition of immunoglobulins A (IgA) and M, C3, C1q, and varicella virus antigen in the glomerulus, suggesting an immune complex deposition. Ultrastructurally, this suggested a postinfectious immune complex glomerulonephritis. These phenomena suggested that varicella virus antigen antibody complexes were deposited in the glomerulus and activated the classic and alternative pathway of complements, leading to an immune complex glomerulonephritis. During the nephrotic phase, an increase in OKT8 cells and decrease of the OKT4 cells were demonstrated. Two months later, this alteration returned to normal as the renal disease was in remission. This change of lymphocyte subsets during varicella infection may play a role in the pathogenesis of nephrotic syndrome.

Inherited complement component deficiencies in membranoproliferative glomerulonephritis.

Anecdotal reports of complement component deficiencies in patients with immune complex disease led to a systematic study of the levels of seven complement components in serum specimens from 178 patients with glomerulonephritis and 163 normal subjects. Deficiencies were found with significantly higher frequency (22.7%) among 44 patients with membranoproliferative glomerulonephritis (MPGN) types I and III, than among the normal subjects (6.7%, P less than 0.002) or among 134 patients with other glomerulonephritides (5.2%, P less than 0.001). The component deficiencies in MPGN were partial in nine patients and subtotal in one. They could not be ascribed to acquired hypocomplementemia or to a nephrotic syndrome. They were present over long periods, were found in family members, and involved C2, C3, factor B, C6, C7, and C8. Six were presumably the result of null structural genes, two were associated with a structurally abnormal component, and two were of unknown cause. The results give evidence that partial deficiency of one or more complement components is a factor predisposing to MPGN.

Consequences of modified fasting in obese pediatric and adolescent patients: effect of a carbohydrate-free diet on serum proteins.

Serum proteins were monitored during three studies of obese adolescents treated with protein-supplemented fasting in a clinical research center. In the first study of nine patients, small but significant decreases were noted for total serum protein, albumin, transferrin, retinol-binding protein, and complement beta 1c after 4 wk of carbohydrate-free protein-supplemented fast. In a further study of four of these same patients, the substitution of 400 glucose cal for 400 fat cal in a 5th wk of dietary study returned the total protein and retinol-binding protein concentrations to base-line levels. In a 3rd study of four patients, only complement beta 1c was significantly below base-line concentrations after 3 wk on a carbohydrate-containing protein-supplemented fast. There is an apparent metabolic effect of carbohydrate ingestion on maintaining usual concentrations of serum proteins.

In vivo metabolism of complement. I. Metabolism of the third component (C'3) in acquired hemolytic anemia.

The in vivo metabolism of purified third component of complement labeled with (125)-iodine (C'3-(125)I) was studied in normal subjects and in patients with acquired hemolytic anemias. 27 such studies were performed; in addition, three studies were performed using C'3i, the biologically inactive reaction product of C'3. In normal subjects the mean fractional catabolic rate of C'3 was 2.12%/hr and the normal range (defined throughout as the mean +/- 2 SD) was from 1.56 to 2.68. The mean percentage of C'3 that was intravascular was 66.6% and the normal range was from 51 to 83. The C'3 synthesis rate averaged 1.16 mg/kg per hr with a normal range of from 0.90 to 1.42. The mean serum concentration of C'3 was 1.43 mg/ml with a normal range of from 1.00 to 1.87. The fractional catabolic rate and synthesis rate of C'3 were at the upper limit of normal or were increased above normal in patients who had warm antibody autoimmune hemolytic anemia with complement on their erythrocytes and in patients with paroxysmal nocturnal hemoglobinuria studied during periods of active hemolysis. An increased C'3 synthesis rate was also found in one patient who was hematologically normal but had an active peptic ulcer and elevated serum concentration of C'3.A normal fractional catabolic rate and C'3 synthesis rate were found in patients with autoimmune hemolytic anemia associated with alpha-methyldopa administration, atypical cold antibody autoimmune hemolytic anemia, and in paroxysmal nocturnal hemoglobinuria during an asymptomatic interval. The three studies with C'3i-(125)I revealed a very rapid removal of the labeled protein from the plasma with less than 10% remaining after 2 hr and with a corresponding increase in urinary excretion rate of the label. The fractional catabolic rate of C'3i averaged 37%/hr. The findings are consistent with the previously elucidated in vitro reaction mechanism of C'3 and strengthen the concept that serum complement participates in immune reactions in vivo.

Experimental production of lethal Escherichia coli bacteremia of pelvic origin.

To reproduce the syndrome of overwhelming Escherichia coli bacteremia and shock after pelvic instrumentation, a model was developed by feeding E. coli via drinking water to coliform-free rabbits, injecting nitrogen mustard intravenously, and inserting a temperature probe into the rectum. The temperature probe was inserted to mimic pelvic instrumentation of patients and to detect fever. Rabbits fed invasive serotypes of E. coli all suffered overwhelming bacteremia with high fever and fatal vascular collapse secondary to invasion of pelvic veins as the granulocyte count approached zero. In the absence of granulocytopenia, the rectal temperature probe produced an intensive inflammation with numerous polymorphonuclears and bacteremia did not develop. In the absence of rectal probing, granulocytopenic rabbits developed high fever without bacteremia. This model resembles human bacteremic shock with respect to the endogenous source of the bacteria, the high frequency of bacteremia due to E. coli and other enteric bacilli, the importance of pelvic instrumentation, and the associated immune disturbances such as granulocytopenia.