Neutrophil function in gram-negative rod bacteremia. The interaction between phagocytic cells, infecting organisms, and humoral factors

Bacterial infections in cynomolgus monkeys given small molecule immunomodulatory antagonists

Opportunistic infections (OIs) during the course of non-clinical toxicity studies can serve as a clinical indicator of immunosuppression. In monkeys, severity may be magnified since the possibility for fecal-oral and cage-to-cage transmission of bacteria exists, reserve capacity is low, and clinical signs of infection are not easily detected until the infectious process is well underway. This review summarizes a case study presented at the HESI-ILSI ITC-Sponsored workshop on Naturally Occurring Infections in Non-human Primates and Immunotoxicity Implications. It gives an overview on the impact of bacterial infections in monkeys on the development and regulatory assessment of three closely-related representative small molecule immunomodulatory (anti-inflammatory) drug candidates all inhibiting the same drug target. The infections, which sometimes progressed to bacteremia and death, originally manifested in the skin, upper respiratory tract, gastrointestinal tract, and less frequently as soft tissue abscesses. Infections were sporadic and not observed in all studies despite coverage of equivalent or higher systemic exposures or longer durations of treatment. To address concerns regarding inconsistency in the presentation and type of findings and their potential relationship to infection, steps were taken to identify causative agents (via culture, microscopy), implement various intervention and treatment regimens (supportive care, antibiotics, drug holiday), demonstrate reversibility of clinical and immune effects, and study major immune components/mechanisms affected (cytokine/stress protein profiling, immune cell phenotyping, and humoral/innate immune cell function tests). Appropriate diagnosis and characterization of the infection was critical to discrimination of these findings as a secondary pharmacologic effect rather than a direct drug-related target organ effect, and also guided clinical protocol design and regulatory acceptance.

Stress doses of hydrocortisone in septic shock: beneficial effects on opsonization-dependent neutrophil functions

OBJECTIVE

To assess the effects of stress doses of hydrocortisone (HC) on clinical parameters and neutrophil functions in patients with septic shock.

DESIGN

Prospective, double-blind, randomized, placebo-controlled study.

SETTING

Intensive care units of a university hospital.

PATIENTS AND PARTICIPANTS

30 adult patients with septic shock.

INTERVENTIONS

Patients were allocated to receive either HC (intravenous bolus of 100 mg preceding a continuous infusion 10 mg/h, n = 15) or placebo (n = 15), respectively. The effects of HC were assessed at baseline and after 24 h.

MEASUREMENTS AND RESULTS

As compared with placebo-treated patients, administration of HC significantly decreased norepinephrine requirements (from 1.5 to 0.8 mg/h; p < 0.001), interleukin-6 serum concentrations (from 388.8 to 88.8 pg/ml; p < 0.02), and the spontaneous release of hydrogen peroxide (H2O2) by neutrophils (-33.0%; p < 0.05). Additionally, HC treatment preserved the autologous plasma-induced amplification of phagocytosis of zymosan particles [factor of opsonin-induced amplification of phagocytosis of unopsonized particles: 1.80 for placebo vs. 1.75 for HC at baseline (not significant between groups) and 0.50 for placebo vs. 1.75 for HC after 24 h of treatment (p < 0.05)]. These effects were paralleled by respective changes in the phagocytosis-associated H2O2 production.

CONCLUSIONS

In patients with septic shock stress doses of HC exert beneficial effects in terms of improvements in hemodynamics, decrease in pro-inflammatory mediators, and oxidative stress without the compromise of opsonization-dependent phagocytic neutrophil functions; thus, HC treatment does not aggravate non-specific immunosuppression but instead improves innate immunity in the early stage of septic shock.

Evaluation of the Scansystem method for detection of bacterially contaminated platelets

BACKGROUND

Platelet (PLT) bacterial contamination occurs in approximately 1 in 2000 PLT units. The College of American Pathologists recommends and AABB requires procedures to detect PLT bacterial contamination. Although two methods, BacT/ALERT (bioMerieux) and Pall BDS (Pall Corporation), have FDA approval for quality control testing, additional methods are in development. One such method was evaluated, the Scansystem (Hemosystem), which has been developed for use on leukoreduced PLT components between 30 and 72 hours after collection.

STUDY DESIGN AND METHODS

Leukoreduced, single-donor apheresis PLT units (LR-SDPs) were inoculated with 10 bacterial species (low and high inocula) associated with PLT contamination. Bacterial detection was compared with the Scansystem and BacT/ALERT. Testing was initiated (10 replicates performed) when LR-SDPs were experimentally inoculated with bacteria. The Scansystem was evaluated 30 hours later, the shortest manufacturer recommended time after PLT collection.

RESULTS

All replicates were positive with the Scansystem at 30 hours and with the BacT/ALERT, at 9.3 to 24.0 hours after inoculation. The Scansystem detected bacteria in 83 of 200 replicates (42%) at the time of inoculation indicating a potential for earlier application.

CONCLUSIONS

The Scansystem, used to test LR-SDPs 30 hours after bacterial inoculation, detected all 20 replicates with a sensitivity equal to the BacT/ALERT system. Based on use of Scansystem with LR-SDPs 30 hours after collection and the BacT/ALERT being inoculated 24 hours after collection and incubated for an additional 24 hours before being determined to be negative, the Scansystem will potentially provide results at an earlier time point (32 hr) than provided by the BacT/ALERT system (48 hr).

Opsonic activity of a new intravenous immunoglobulin preparation: Pentaglobin compared with sandoglobulin

Standard preparations of immunoglobulin for intravenous use consist predominantly of IgG (greater than 95%). We have compared the ability of a standard preparation (Sandoglobulin) with that of a new preparation (Pentaglobin, containing 12% IgM and 12% IgA) to improve the opsonic activity of antibody-deficient human sera in vitro. Panhypogammaglobulinaemic sera were poorly opsonic for five of six organisms tested, particularly Pseudomonas aeruginosa, Escherichia coli and Streptococcus pneumoniae, but opsonized Staphylococcus aureus almost normally. Both immunoglobulin preparations significantly improved the opsonic activity of the antibody-deficient sera for most organisms. The major difference between the two preparations was the ability of Pentaglobin to supply opsonins for P. aeruginosa, E. coli and Klebsiella pneumoniae, while Sandogloblin was significantly more potent in opsonins for Haemophilus influenzae. Pentaglobin demonstrates significant in vitro opsonic activity, particularly for enterobacteria (coliforms) and P. aeruginosa. Its content of IgM antibodies appears to confer special properties on Pentaglobin not seen with standard preparations of immunoglobulin for intravenous use. Its place in clinical practice remains to be determined but it may have a possible role in augmenting host defence mechanisms in Gram-negative septicaemia.

[Measuring chemiluminescence in phagocytic granulocytes--simultaneously a parameter of their killing function?]

The results of the chemiluminescence activity determined in whole blood samples very often were used to compare the unspecific defense mechanism of polymorphonuclear granulocytes (PMN) against causative organisms to preoperative capable risk parameters in surgery. Our investigations try to compare the results of a bacteria-induced chemiluminescence with those we received from a standardized agar killing plate-test. It could be shown that there is no correlation between the used two test systems. Therefore it is not possible to conclude from the chemiluminescence results especially made out of whole blood samples to the potency of the defense mechanism of PMN granulocytes.

Urinary tract infections and renal papillary necrosis in alcoholism

An enhanced frequency and morbidity of urinary tract infections (UTI) have been observed in association with alcoholism and liver disease. The causes of these phenomena may relate, in part, to the defects in humoral and cellular immune mechanisms that occur in alcoholism. Urinary catheterization is the most common cause of UTI in hospitalized alcoholics. The severity of the sequelae of UTI in alcoholism is demonstrated by the unusually frequent occurrence of renal papillary necrosis (RPN) in conjunction with pyelonephritis in these patients. Indeed, in over 90% of the reported cases of RPN occurring with alcoholism or liver disease, pyelonephritis has been a contributing factor. The proclivity to medullary ischemia and RPN in this patient group may be, at least in part, a result of interstitial renal edema secondary both to infection and the effect of ethanol per se and to renal arterial vasoconstriction that occurs in cirrhosis. The frequency with which death due to sepsis or renal failure occurs in association with UTI in alcoholics obliges the physician to exercise caution in the prevention and treatment of UTI in these patients.

Escherichia coli in extra-intestinal infections

When Theodor Escherich (1885a, b) first describedEscherichia colihe looked on it as a saprophytic organism. Soon several investigators found that colibacteria could be isolated from intestinal infections and from many infections outside the intestine, like urinary tract infections (UTI), cholecystitis, wound infections, meningitis, septicaemia, pulmonary infections, and many more. Uhlenhuth (1897) showed that coli strains from pathological processes were more pathogenic in animal experiments than strains isolated from the normal intestine. Smith (1927), who examined strains from white scours in calves, showed that spontaneous acapsular mutants could be obtained from certain colibacteria, and that such mutants were less virulent when injected intra-peritoneally into guinea-pigs.

Role of opsonins in clinical response to granulocyte transfusion in granulocytopenic patients

Fifty febrile severely granulocytopenic patients were given four daily transfusions of 2.2 X 10(10) normal donor granulocytes. Twenty-three (46 percent) responded clinically, although both responders and nonresponders were similar in clinical characteristics at the outset. This study examines the relation between serum opsonic activity before initiation of granulocyte administration and clinical response. Opsonic activity to three test organisms (Escherichia coli 286 and ON 2, and Staphylococcus aureus) and to 15 blood stream isolates from 14 patients was measured as serum-dependent uptake of heat-killed 14C-labeled bacteria by normal donor leukopheresis granulocytes in an in vitro assay and compared with results obtained with a standard normal serum in each assay. At a concentration of 8 percent serum, all patient groups were equivalent to standard (90 to 102 percent) for the three test organisms. When rate-limiting concentrations of serum (1 to 2 percent) were employed, opsonic activity remained similar to standard for S. aureus in all patient groups and for the two E. coli strains in responders (82 to 98 percent). In contrast, opsonins for E. coli decreased to 41 to 50 percent of standard in nonresponders (p less than 0.01). When patients with proved infection were separately analyzed, opsonin activity for E. coli 286 and ON 2 was significantly greater in responders than nonresponders (73.6 versus 34.9 percent and 124.8 versus 58.1 percent, respectively for the two strains) (p less than 0.01). Patients with opsonin activity of 50 percent or greater of standard had a greater response rate (73 versus 19 percent and 45 versus 0 percent for the two E. coli strains) (p less than 0.005 and p = 0.08, respectively). Eight of 10 patients with 75 percent or greater of standard for opsonic activity against their own blood stream isolates also responded, whereas zero of four with opsonins less than 75 percent of standard had a favorable outcome. These results indicate that serum opsonic activity may be a determinant of clinical response to granulocyte transfusion in infected granulocytopenic patients and may be predictive of outcome. We conclude that opsonic activity should be assessed in such patients before granulocyte administration and suggest a trial of plasma infusion in opsonin-deficient patients.

Polymorphonuclear leukocyte function in bacterial and viral infections

Chemiluminescence (CL) production by polymorphonuclear leukocytes (PMNLs) was examined in 63 patients with bacterial infections and 63 healthy controls. The production was significantly higher in the patients (mean +/- standard error = 134.5 +/- 5.0 X 10(3) cpm) than in the controls (118.9 +/- 2.5 X 10(3) cpm; p less than 0.05). In 38 patients CL values were within the normal range and in 19 patients above. CL production below that of any control occurred in 6 patients: 3 (of 4) with staphylococcal endocarditis, 2 (of 4) with pneumococcal meningitis and 1 with salmonella septicaemia and osteomyelitis. PMNL hexose monophosphate shunt activity as measured by glucose metabolism correlated with CL production. Patients with low CL production more often had large numbers of juvenile and immature myeloid cells in the peripheral blood than patients with normal or high CL values. 3/6 patients with low CL values died, 2/38 with normal and 0/19 with high values. Directed and spontaneous PMNL migration was examined in 39 of the 63 patients with bacterial infections. 13 patients had PMNLs with higher directed and 16 with higher spontaneous migration capacity than their corresponding controls. The remaining patients had PMNLs with lower migration capacity. 2 of the 39 patients died. Each had PMNLs with low migration capacity. CL production by PMNLs was examined in 16 patients with viral infections and 16 healthy controls. The production was significantly lower in the patients (mean +/- standard error = 105.5 +/- 6.6 X 10(3) cpm) than in the controls (129.1 +/- 5.3 X 10(3) cpm; p less than 0.01). 15 patients had lower values than their corresponding controls. The PMNL migration capacity was also lower in the patients. These findings indicate that the majority of patients with bacterial infections have PMNLs with normal or increased function. However, some patients have reduced PMNL function and this reduction may contribute to a fatal outcome of the disease. Patients with viral infections usually have reduced PMNL function.

Phagocytic and bactericidal activity of human neutrophils against two isolates of Group B streptococci Type Ic of differing pathogenicity

The phagocytic and bactericidal activities of normal adult human neutrophils against 2 strains of Group B streptococci Type Ic of differing pathogenicity were examined. Both isolates were phagocytosed by the neutrophils in the presence of normal and homologous immune serum. However, the highly pathogenicity streptococci were killed less readily in the presence of immune serum than were the streptococci of low pathogenicity in the presence of immune or normal serum. This difference in killing ability was not due to a defect in phagocytosis by the neutrophils, but to a defect in bactericidal activity. The highly pathogenic streptococci were not killed in the presence of normal serum, but were readily phagocytosed by the neutrophils, in which they accumulated and eventually caused their destruction. The streptococci of low pathogenicity, however, were killed equally as well in the absence of specific antibody as in its presence. It is suggested that an in vitro assessment of neutrophil function against streptococci of differing pathogenicity for mice may provide a useful method by which the pathogenicity of streptococci for man can be compared.

Immunological aspects to severe bacterial sepsis

In spite of discovery of new antibiotics and regular progress in intensive care, mortality from severe bacterial sepsis remains high. In this review the importance of cellular and humoral immunity in the pathogenesis and the outcome of severe infection is delineated. Immunological evaluation of patients in Intensive Care Units should be performed almost routinely in order to detect "high risk" patients with acquired defect in host-defence mechanisms. For these patients in addition to nutritional care, passive or active immunotherapy will help to restore resistance to bacterial infection.

Hemolysin and K antigens in relation to serotype and hemagglutination type of Escherichia coli isolated from extraintestinal infections

Escherichia coli isolated from cases of bacteremia and from a variety of urinary tract infections were characterized according to serotype (O:H antigenicity), K type (possession of K1, K2, K3, K12, or K13), hemagglutination (HA) type, and production of beta-hemolysin. Results obtained with the bacteremia and urinary tract infection isolates were similar except for more hemolytic isolated from urine than from blood (42 versus 29%) and more K1+ isolates from blood than from urine (50 versus 29%). A close correlation was found between Ha type VI (production of fimbriae which mediate mannose-resistant HA of human and African green monkey erythrocytes) and the production of hemolysin or K1 capsular antigen or both. Most (95 of 98, or 95%) of the HA type VI+ blood isolates and most (146 of 164, or 89%) of the HA type VI+ urine isolates produced hemolysin or K1 or both, in contrast to 22 and 26%, respectively, of those belonging to HA types other than HA type VI. Also, 76% of all hemolytic and 70% of all K1+ isolates belonged to HA type VI. Remarkably few of the HA type VI+ isolates (13%) and even fewer of the HA type VI- isolates (3%) produced both K1 and hemolysin; these belonged mainly to serotypes O16:H6, O18:H7 and O2:H4. Other major serogroups were usually K1+/hemolysin- (O1, O7) or K1-/hemolysin+ (O2, O4, O6). At least 74% (262 of 351) and possibly as many as 83% (293 of 351) of those isolates which produced mannose-resistant HA of human erythrocytes were classified as HA type VI+; 31 isolates produced mannose-resistant HA with all erythrocytes tested. Taking serogroup and serotype into consideration, we conclude that the E. coli fimbrial hemagglutinin(s) responsible for the HA type VI phenotype will prove to be the same as the virulence-associated mannose-resistant adhesins of uropathogenic E. coli which other investigators have characterized as unique fimbrial antigens detectable by mannose-resistant HA of human erythrocytes.

Bacteremic infection and malnutrition in patients with solid tumors: investigation of host defense mechanisms

Eighty-five patients with solid tumors without neutropenia were studied in order to determine host characteristics associated with bacteremic infection. Twenty patients without neoplastic disease who had bacteremia served as controls. Bacteremia frequently occurred in patients with tumors of the gastrointestinal and urinary tract, who were over 51 years of age, and had evidence of malnutrition. Peripheral blood lymphocyte dysfunction in vitro was commonly noted in infected patients with cancer. Polymorphonuclear leukocyte (PMNL) dysfunction was common in older bacteremic patients with and without cancer. The PMNL abnormality appeared to be cellular, it was not corrected with use of pooled normal serum, and was manifested by poor uptake of the assay organisms.

Relative opsonic and protective activities of antibodies against K1, O and lipid A antigens of Escherichia coli

The K1 Escherichia coli capsular antigen has been implicated as a virulence factor because of the frequency of isolation of K1 containing strains from certain invasive human infections. In the study of the interaction between K1 strains, normal human polymorphonuclear cells (PMNs) and fresh human serum, we have found varying susceptibility to phagocytosis and killing; thus, the in vitro opsonophagocytic and in vivo protective role of K1, somatic O and core glycolipid antibodies remain unclear. We have therefore examined strains of E. coli with defined susceptibility to phagocytosis by normal PMNs and sera and compared the effect of K1, somatic O and lipid A antibodies in opsonophagocytic tests and mouse protection experiments. K1 E. coli strains demonstrating relative resistance to phagocytosis and killing were effectively opsonized only with specific K1 capsular antisera. Similarly, K1 capsular antisera, but not anti-O or lipid A antisera, also provided protection in mice challenged with a LD100 of K1 E. coli that were "resistant" to phagocytosis. The ability of purified capsular antigens from Neisseria meningitidis group B and K1 "resistant" E. coli to inhibit the phagocytosis of a "sensitive" non-K1 and a K1 E. coli strain of "intermediate" susceptibility to opsonophagocytosis was also investigated. Purified K1 and group B capsular antigens were able to block specific capsular-antibody mediated opsonophagocytosis, yet these capsular antigens failed to inhibit the phagocytosis of non-K1 "sensitive" or K1 "intermediate" E. coli. These studies suggest that K1 antibodies are obligatory for the in vitro and in vivo opsonophagocytosis of "resistant" K1 E. coli and that the K1 antigen must remain in situ on the bacterial surface to exert an anti-phagocytic effect.

Decreased heat-labile opsonic activity and complement levels associated with evidence of C3 breakdown products in infected pleural effusions

Heat-labile opsonic activity was measured simultaneously in serum and pleural fluid of patients with transudates, infectious exudates (with positive or negative bacterial culture) and neoplastic exudates, using two different complement-dependent phagocytic tests: the killing of Staphylococcus aureus Wood 46 variant strain (K50 opsonic titers) and the assessment of ingestion rate of endotoxin-coated paraffin particles (Oil Red 0 uptake test). K50 opsonic titers were lower in culture-positive pleural effusions as compared to culture-negative (P < 0.002) or neoplastic effusions (P < 0.002). These results were corroborated by the Oil Red 0 uptake test. The data obtained with the two assays showed a significant correlation (P < 0.001). The hemolytic activity of complement (CH50) as well as the levels of C3 breakdown product, C3d, were measured in the same sera and pleural fluid samples and in an additional group of patients with pleural effusions of the same etiology. Effusions with positive cultures showed lower CH50 values (P < 0.01) and higher C3d values (P < 0.05) when compared to culture-negative pleural fluids. Finally, evidence for immune complexes in pleural effusions and sera was looked for by determination of Clq binding activity. Levels were higher in culture-positive effusions when compared to culture-negative fluids (P = 0.005).K50 opsonic titers showed a positive correlation with CH50 values (P < 0.001) for all fluids tested. Similarly Clq binding activity correlated with C3d levels in effusions of infectious origin (P = 0.05). Recovery experiments using the various bacterial species isolated from culture-positive pleural effusions showed evidence of complement inactivation upon incubation with pooled sera at concentrations of 10(7)-10(8) microorganisms/ml. These results indicate that one important reason for bacterial persistence in empyema may be decreased opsonization secondary to local consumption of complement.

A sequential, prospective analysis of immunologic abnormalities and infection following severe thermal injury

A sequential, prospective analysis of humoral and cellular immune function was performed on 20 burn patients with injuries involving >/=45% total body surface area. Infected patients had significantly worse neutrophil bactericidal activity against Staphylococcus aureus 502A than did noninfected patients. Chemotaxis of neutrophils correlated poorly with infection although chemotaxis was frequently abnormal. The opsonic index of serum was depressed early after the burn but returned to nearly normal values by the fourth to the fourteenth postburn day. There was no difference between infected and noninfected patients. Serum levels of IgG, properdin and C3, while initially low, remained within the normal range after the ninth postburn day in both groups. Factor B levels rose rapidly during the first three weeks after injury to more than double normal levels in many patients. Suggestive evidence for consumption of opsonic protein occurred with five of 19 episodes of bacteremia. The responsiveness of isolated lymphocytes to PHA was normal. However, patients' sera were shown to significantly inhibit the responsiveness of normal lymphocytes to PHA. Analysis of immunologic profiles for individual patients indicates that abnormalities of neutrophil function are the most important acquired defect predisposing patients to the development of bacteremia following major thermal injury; abnormalities of opsonic action play a secondary but important role.

Phagocytic resistance of Escherichia coli K-1 isolates and relationship to virulence

Blood culture isolates from 133 episodes of Escherichia coli bacteremia were typed for K-1 capsular antigen by immunodiffusion, utilizing equine antiserum raised against meningococcal group B polysaccharide. Twenty-six percent (34 of 133) of these isolates were positive for K-1 antigen. These 133 strains, 34 K-1 and 99 non-K-1, were tested for susceptibility to phagocytosis. K-1 strains were found to be more resistant to clearance (27%) than non-K-1 strains (71%) when tested in an in vitro opsonophagocytic/killing assay containing normal human granulocytes and plasma. Additional studies demonstrated that resistance was due to decreased phagocytosis rather than diminished intraleukocytic killing. K-1 strains obtained from stool showed a similar degree of resistance to phagocytosis when compared with K-1 blood isolates. A comparison of clinical data on non-neonatal patients with E. coli K-1 and non-K-1 bacteremia showed no significant differences in mortality for these two groups. The incidence of shock for patients bacteremic with K-1 strains (74%) was significantly greater than that for patients bacteremic with non-K-1 strains (33%). These differences are attributed to the increased resistance to phagocytosis observed for K-1 versus non-K-1 E. coli isolates.

In vitro evaluation of opsonic and cellular granulocyte function by luminol-dependent chemiluminescence: utility in patients with severe neutropenia and cellular deficiency states

Actively phagocytizing polymorphonuclear leukocytes (PMN) emit light or chemiluminescence (CL) which has been shown to be linked to the oxidative activity of the PMN. The measurement of CL has been demonstrated to be a useful tool for the in vitro assessment of intracellular and opsonophagocytic function of PMN. We have increased the sensitivity of the CL measurement by the addition of luminol to the in vitro reaction of PMN, bacteria, and serum. The presence of luminol, which can be oxidized to emit light, amplifies the detection of CL and PMN cellular activity. This amplification effectively reduces the number of PMN that are necessary for assessment of PMN function from 1 x 10(7) to as low as 2 x 10(4) PMN/assay and permits the evaluation of PMN function in severely neutropenic patients (100 PMN/mm3) in whom cellular PMN function has been heretofore extremely difficult to assess by other methodology. When this luminol-dependent CL method was used, three of eight neutropenic leukemic patients with gram-negative septicemia were found to have deficient opsonic activity and/or increased or depressed cellular oxidative activity. Because the initial slope of CL is dependent on the amount of serum and heat-labile factors, this method can also be used effectively as a simple technique for the analysis of specific rates of opsonophagocytosis of various microorganisms. Additionally, this method can detect the cellular PMN abnormalities of chronic granulomatous disease and myeloperoxidase deficiency. The luminol-dependent CL method is a simple, sensitive, reproducible technique that provides useful information about PMN metabolic activity, particularly in studies in which the number of PMN is limited.

Intracellular lambda light chain inclusions in chronic lymphocytic leukaemia

A case of chronic lymphocytic leukaemia (CLL) with intracytoplasmic crystalline inclusions in peripheral blood lymphocytes is presented. The inclusions were identified as crystals of lambda (lambda) light chain and were present in bone marrow derived (B-cells) lymphocytes. The occurrence of light chain crystals in CLL may reflect a more primitive defect in immunoglobulin (Ig) synthesis, intracellular transport or secretion than has previously been reported.

Phagocytosis. Clinical disorders of recognition and ingestion

Tentative conclusions concerning the role of recognition and ingestion of microorganisms by phagocytes in host defense and the consequences of disorders of phagocytosis can be derived by correlating a) knowledge about recognition and ingestion derived from studies in vitro, b) investigations of the clearance of particulate matter from the circulation of animals and man, and c) analyses of the behavior of phagocytes in patients susceptible to recurrent pyogenic infections. Deficiency of the major serum recognition-conferring (immunoglobulins and complement proteins that deposit a fragment of C3 on microbes) prevents the optimal clearance of virulent encapsulated pathogens by fixed mononuclear phagocytes. Confrontation of phagocytes with particulate matter appearing in pathologic states (viruses, immune complexes, damaged erythrocytes in sickle cell anemia and other hemoglobinopathies) diverts them from their normal task of clearing opsonized encapsulated microorganisms. Corticosteroids impair the phagocytic capacity by an unknown mechanism. Major impediments to progress in this field are inadequate assays for phagocytosis and the difficulty in measuring phagocytosis in the intact organism.

Correlation between the susceptibility of E. coli to phagocytosis and their ability to invade HeLa cells in vitro

The susceptibility of several strains of E. coli to phagocytic killing by polymorphonuclear lencocytes and the ability of the same strains to invade HeLa cells were studied. It was found that only the strains resistant to killing by leucocytes were able to penetrate and multiply within HeLa cells.

Quantitative granulocyte chemiluminescence in the rapid detection of impaired opsonization of Escherichia coli

Previous work has demonstrated that 40% of clinically isolated Escherichia coli are resistant to in vitro killing by normal human polymorphonuclear granulocytes (PMN) due to ineffective opsonophagocytosis. Using these E. coli isolates, we have demonstrated the usefulness of measuring the chemiluminescence (CL) of granulocytes undergoing phagocytosis in detecting this impaired opsonization. CL correlated well with several other methods to assess PMN function including in vitro killing assays, postphagocytic O2 consumption, and morphological phagocytic indexes. Of the available methods to assess granulocyte function, CL is the most rapid and simple and would appear to be a potentially useful screening method to determine possible opsonic deficiencies of human PMNs and serum. Impaired opsonization to these resistant E. coli isolates was demonstrable in several different donors and could be reversed by type-specific rabbit antibody to the particular resistant isolate. Bacterial levels of superoxide dismutase and catalase, enzymes which have been implicated as possible virulence factors in some microorganisms, did not correlate with resistance in these E. coli isolates. However, heat denaturation of these isolates reversed this resistance and would suggest heat-labile antigenic determinants present in E. coli as possible resistance factors.