Serum phospholipase A2 correlates with disease activity in rheumatoid arthritis

We previously demonstrated a marked elevation of the proinflammatory enzyme phospholipase A2 (PLA2) in all synovial fluids and some sera of patients with rheumatoid arthritis (RA). Since PLA2 was found to induce inflammatory changes in the skin and joints of experimental animals, we tested whether the serum level of PLA2 correlates with the clinical activity of RA. In the group of 51 patients with classical or definite RA, 13 (25%) had high serum levels of PLA2 (over 2 standard deviations above the normal mean). Comparison of clinical disease activity in patients with high levels of PLA2 with those with normal PLA2 levels showed that patients with high PLA2 levels had a significantly higher joint count, more swollen joints, much higher Landsbury index, lower functional class, lower hemoglobin, lymphopenia and higher erythrocyte sedimentation rate (ESR). To more accurately assess the relationship between the PLA2 level and disease activity in RA, we formulated 2 indices. Clinical index consisted of the Landsbury index, number of swollen joints and duration of morning stiffness. Laboratory index consisted of hemoglobin, absolute number of peripheral blood lymphocytes, platelet count and ESR. Our results showed that both indices correlated strongly with PLA2 activity (p less than 0.0001). The results support the hypothesis that PLA2 plays a pathogenetic role in RA and suggest that serum PLA2 levels may serve as an additional measure of disease activity.

Concordance of endogenous cortisol and phospholipase A2 levels in gram-negative septic shock: a prospective study

Lipocortins, a group of corticosteroid-induced phospholipase-inhibitory proteins, are thought to play a prominent role in the mediation of the anti-inflammatory effects of steroids. The synthesis and release of these proteins may represent a major endogenous mechanism of regulation of extracellular phospholipase A2 (PLA2) activity. Because soluble PLA2 activity has been associated with circulatory collapse in hyperphospholipasemic conditions, such as septic shock and pancreatitis, we examined the relationship between circulating PLA2 activity and adrenocortical function. In a prospective study of 10 episodes of septic shock, serum PLA2 and cortisol levels correlated significantly in all survivors (p less than 0.0001), whereas such a correlation was absent in all nonsurvivors (p less than 0.07). No significant correlation of cortisol and adrenocorticotropic hormone (ACTH), or PLA2 and ACTH, was found in any patient, suggesting that the stimulus for cortisol release arises from outside the hypothalamic-pituitary axis. These data suggest that, in human beings, the regulation of soluble PLA2 activity may be mediated by adrenocortical hormones, perhaps through the intermediary action of lipocortins.

Influence of cationic superoxide generation enhancing protein (SGEP) on phagocytic and intracellular bactericidal activity of human polymorphonuclear cells

Cationic fraction III from the lysosomes of normal human peripheral blood polymorphonuclear cells (PMNs) was found to contain superoxide generation enhancing protein (SGEP). Herein, we report on the influence of partially purified SGEP obtained from fraction III (subfractions III-5 and III-6), on various phagocytic functions of human PMNs. SGEP markedly enhanced intracellular bactericidal activity of human peripheral PMNs. The enhancement was time and dose dependent. It also reduced adhesiveness of the PMNs. SGEP did not influence chemotaxis, phagocytosis or phagocytic index. These findings are compatible with our original observation regarding superoxide generation enhancement properties of SGEP.

Comparative study of phagocytosis and intracellular bactericidal activity of human monocytes and polymorphonuclear cells. Application of fluorochrome and extracellular quenching technique

Simultaneous assessment of the total number of bacteria (TNB) ingested, phagocytosis (Ph), phagocytic index (PI), and intracellular bactericidal activity (ICBA) of human monocytes was done by applying the fluorochrome acridine orange technique. Living bacteria stained orthochromatically green, whereas the dead ones were metachromatically red. The stain of extracellular bacteria was completely quenched by crystal violet counterstain. Using the Hypaque-Ficoll separation method combined with glass adherence, the yield of monocytes was 84 +/- 11%, the purity 90 +/- 8%, and the viability 99 +/- 1%. After 60 min of incubation of monocytes with Staphylococcus aureus, phagocytosis was 94 +/- 4%, PI 10.0 +/- 0.5, ICBA 76 +/- 5%, and TNB ingested 946 +/- 67/100 cells. E. coli B4 was equally ingested by PMNs and monocytes and killed intracellularly more efficiently by the latter type of cells. Over the ratios of bacteria to cells of 5:1 to 20:1, phagocytic activity of monocytes was equal or superior to that of PMNs. Phagocytic and bactericidal activities were enhanced by AB serum, more by the fresh one than by inactivated. Phagocytic activity of monocytes was markedly influenced by temperature of incubation. Room temperature (24 degrees C) significantly suppressed phagocytosis. Contrary to the previous beliefs no significant quantitative differences were found between phagocytic and bactericidal functions of monocytes as compared to polymorphonuclear phagocytes. The acridine orange-crystal violet method is simple, reliable, reproducible, and can be used for assessment of functional capacity of human phagocytes.

Pathogenesis of hypotension in septic shock: correlation of circulating phospholipase A2 levels with circulatory collapse

Circulating phospholipase A2 (PLA2) has been recognized as a mediator of circulatory collapse in experimental endotoxic shock. To assess the role of serum PLA2 in septic shock in man, we determined serum PLA2 profiles in a prospective study in 12 patients with septic shock. During the hypotensive phase of sepsis, serum PLA2 levels were consistently elevated as high as 33,428 U/ml (normal range 115 +/- 12 [SE]; n = 101). In all 12 patients, PLA2 levels correlated directly with the magnitude and duration of circulatory collapse (p less than .001), with a progressive fall of serum PLA2 levels during convalescence. In contrast, serum PLA2 levels in patients with cardiogenic shock secondary to myocardial infarction remained low. In pancreatitis, PLA2 levels paralleled fluctuations of serum amylase and lipase, whereas in septic shock without pancreatic involvement, PLA2 changes were discordant with changes in pancreatic enzymes. As well, septic shock serum PLA2 failed to crossreact by radioimmunoassay with antiserum against human pancreatic PLA2. These data are consistent with an extrapancreatic source of intravascular PLA2 release during sepsis. Since endogenous serum PLA2 levels correlate directly with the magnitude of hypotension in both experimental endotoxic shock and clinical septic shock, and since parenteral administration of purified exogenous PLA2 reproduces hypotension in experimental models, we conclude that high levels of intravascular PLA2 may contribute similarly to the circulatory collapse in septic shock in man.

Cryptic cold agglutinin activity of monoclonal macroglobulins

One hundred and twenty sera with monoclonal immunoglobulin M's (IgM's) were tested for cryptic cold agglutinin activity against papain- and neuraminidase-treated adult and cord red blood cells (RBC). Fifteen sera (12.5%) agglutinated papain-treated RBC. Fourteen of these 15 sera also agglutinated neuraminidase-treated RBC. Ten additional sera agglutinated neuraminidase-treated but not papain-treated cells. Three patterns were observed among agglutinators of papain-treated RBC: either predominant agglutination of adult RBC, or of cord RBC or equal reaction, thus resembling I, i and non-Ii patterns of conventional cold agglutinins. We propose to call these patterns, tentatively, Icr (cr for cryptic), icr, and non-Iicr, respectively. Purified monoclonal IgM's retained the above patterns. Eluates from enzyme-treated cells contained monoclonal IgM's. Investigation of neuraminidase-treated RBC has shown that in distinction to T-anti-T system (Thomsen-Friedenreich receptor system), the majority of sera with monoclonal IgM's agglutinated more strongly adult RBC, and some agglutinated more strongly cord RBC. There was no loss of agglutinating activity after repeat freezing and thawing of the sera. Thus, it seems that monoclonal IgM's which react with neuraminidase-treated RBC detect antigenic determinants different from the T antigen. Cryptic CA activity of IgM's should be added to the list of antibody activities of these monoclonal immunoglobulins.

Influence of neutrophil cationic proteins on generation of superoxide by human polymorphonuclear cells during phagocytosis

The cationic proteins from neutrophil lysosomes have been shown to modulate phagocytic activity of granulocytes. The present study reports the effects of the cationic protein fractions on the generation of O2- by human PMNs during phagocytosis. Human PMNs were reacted with different phagocytic stimuli in the presence and absence of lysosomal cationic proteins and the amount of O2- generated was determined by superoxide dismutase inhibitable reduction of cytochrome c. Total cationic protein extract from neutrophil lysosomes enhanced O2- generated by PMNs during the phagocytosis of IgG-coated latex beads and opsonized zymosan particles. The analysis of the fractions of cationic proteins obtained from a Sephadex G-75 column showed that the O2- generation-enhancing activity was associated with the proteins eluted in fractions III and IV. A protein fraction mainly eluted in void volume inhibited the cytochrome c reduction by O2- formed during phagocytosis. This was due to the presence of superoxide dismutase-like activity since O2- generated by the xanthine-xanthine oxidase system was also inhibited by this fraction. The cationic protein fractions III and IV from the Sephadex G-75 column were further subfractionated. Although the O2(-)-enhancing activity was eluted in the same fractions as chymotrypsin activity, there was no quantitative correlation between the amount of O2- generation and chymotrypsin activity. Moreover, commercial chymotrypsin did not enhance O2- generation. Electrophoretic analysis of the isolated protein fractions suggests that O2- generation enhancing protein (SGEP) is different from lysozyme or chymotrypsin and probably represents previously undescribed protein.

Antinucleic acid autoantibody responses of normal human origin: antigen specificity and idiotypic characteristics compared to patients with systemic lupus erythematosus and patients with monoclonal IgM

One idiotype family 4.6.3 derived from a human hybridoma IgML monoclonal anti-DNA antibody of normal origin is commonly expressed (approximately 85%) in the serum of patients with systemic lupus erythematosus but not in normal controls, where its level appears to fluctuate with clinical disease activity. In contrast, the IgM released by normal cultured lymphocytes in vitro expresses this idiotype family but does not bind DNA. Both idiotype 4.6.3 and anti-DNA antibodies are frequently detectable in the serum of patients with monoclonal IgM but not IgG. Therefore, it is likely that idiotype 4.6.3 reflects the expression of a common germ line immunoglobulin gene family. Some of the IgM molecules encoded by these germ line immunoglobulin genes also bind DNA.

Lymphocytotoxins in vasculitis. Correlation with clinical manifestations and laboratory variables

Twenty-eight of 53 patients with various types of vasculitis were found to have cold reacting lymphocytotoxins (LCT). LCT were cytotoxic to both peripheral blood B and T cells as well as to OKT4 and OKT8 subpopulations. The interaction with the B cells was more pronounced than with the T cells as shown by reactivity with the former at higher serum dilutions than with the latter. Similar results were obtained with eluates from the unseparated lymphocytes and from B or from T cells. Partial purification of LCT demonstrated that they belong to the IgM class. LCT correlated with the level of circulating immune complexes as determined by the fluid phase C1q binding assay, but they did not correlate with the level of immunoglobulins, complement or antinuclear factors. The presence of LCT correlated significantly with the activity but not with the disease duration or the number of involved organs. Correlation of LCT with the activity of vasculitis implies that these cytotoxins may have a pathogenetic role and perhaps may serve as a marker for disease activity.

Purification of a soluble phospholipase A2 from synovial fluid in rheumatoid arthritis

A soluble phospholipase A2 (PLA2) was purified 4,500-fold from human rheumatoid synovial fluid. Preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis yielded two bands of PLA2 activity of molecular weights 15,000 and 17,000 and pl 4.2-5.0. Purified PLA2 had absolute 2-acyl specificity, and hydrolyzed phosphatidylcholine with optimal activity at pH 7.5-8.0 and phosphatidylethanolamine with optimal activity at pH 7.0. Human synovial fluid PLA2 did not cross-react with anti-human pancreatic PLA2, as tested by radioimmunoassay.

Potential therapeutic efficacy of inhibitors of human phospholipase A2 in septic shock

Soluble phospholipase A2 has been implicated in the pathogenesis of local and systemic inflammatory reactions. Elevated levels of circulating phospholipase A2 (PLA2) correlate with the severity of circulatory collapse and pulmonary dysfunction in gram-negative septic shock. Characterization of septic shock serum PLA2 revealed a calcium-dependent enzyme with absolute 2-acyl specificity with a pH optimum of 7.5. We tested a number of therapeutic agents for their ability to inhibit PLA2 from human septic shock serum. Chloroquine, chlorpromazine, dexamethasone base, dexamethasone sodium phosphate, indomethacin, lidocaine, oleic acid, palmitic acid, promethazine, trans-retinoic acid, rutin and dl-alpha-tocopherol were all studied over the range of 10(-2) to 10(-7) M. All agents, with the sole exception of dexamethasone base, inhibited PLA2 activity at concentrations greater than 10(-3) M. PLA2 inhibition by dexamethasone sodium phosphate was factitious, due to the formation of calcium-phosphate complexes. Of the 11 agents studied, chlorpromazine was the most effective, with an IC50 of 7.5 X 10(-5) M, a membrane concentration achievable within its therapeutic range. Inhibition was non-competitive with an apparent Ki of 5 nM. Since serum PLA2 levels correlate with mortality in both experimental endotoxemia and clinical gram-negative septic shock, and chlorpromazine was previously shown to improve survival in these conditions, we postulate that its therapeutic efficacy resides at least in part in its PLA2-inhibitory activity.

Suppression of chemotactic activity of human polymorphonuclears by monoclonal IgMs with and without biological activity

The influence of monoclonal IgMs on migration of human polymorphonuclears was studied at various temperatures by the use of 19 sera with monoclonal IgMs from patients with macroglobulinemia of Waldenstrom (MW) without obvious biological activity, 29 sera with monoclonal IgM cold agglutinins (18 with anti-I and 11 with anti-i IgMs) and 3 sera with monoclonal IgM rheumatoid factor (RF). Under-agarose migration method and modified Boyden chamber method with double filters and 51Cr-PMNs were used. In under-agarose method, chemotactic differentials for controls, MW, anti-I, and anti-i groups were, respectively, 57 +/- 8 mm, 39 +/- 9 mm, 44 +/- 14 mm, and 32 +/- 16 mm at 37 degrees C and 47 +/- 18 mm, 22 +/- 11 mm, 17 +/- 9 mm, and 15 +/- 12 mm at 24 degrees C. All three sera with IgM RF inhibited chemotaxis. The differences between all groups and controls were significant at p less than 0.01. Random migration was inhibited at 24 degrees C (p less than 0.01) but not at 37 degrees C. Inhibitory concentrations of IgM in the sera tested were equal or less than 0.5 mg/ml. Thirteen sera were tested by the modified Boyden chamber method. At 37 degrees C 8 of 13 sera and at 24 degrees C 11 of 13 sera inhibited significantly chemotaxis at a concentration of IgM of 1 mg/ml. The lowest inhibitory concentration of IgM was 25 micrograms/ml. Eleven chromatographically pure IgMs were tested in the under-agarose assay. At concentrations of 0.4-3.7 mg/ml, eight IgMs inhibited chemotactic differential at 37 degrees C and nine inhibited it at 24 degrees C. At concentrations of 0.6-2.0 mg/ml, all seven pure IgMs tested by the Boyden chamber method significantly inhibited chemotaxis at 24 degrees C and 37 degrees C. Some IgMs inhibited chemotaxis at concentrations as low as 25 micrograms/ml. Ten IgM CA were eluted from the red blood cells. Eluates inhibited strongly chemotaxis at 24 degrees C and 37 degrees C. Heat inactivation did not alter inhibitory activity of IgM, however pepsin digestion or reduction and alkylation of purified IgMs did abolish their inhibitory activity. Inhibition of chemotaxis was not related to the light chain type, the titre, or the thermoamplitude of cold agglutination. However, monoclonal IgMs with anti-i cold agglutinin activity were stronger inhibitors than anti-I. Since 75% of IgMs tested inhibited chemotaxis at 37 degrees C, it is possible that monoclonal IgMs, especially those with anti-i cold agglutinin activity, inhibit PMN migration in vivo.

Influence of plasma proteins on activity of proinflammatory enzyme phospholipase A2

The influence of plasma proteins on quantitation of the proinflammatory enzyme phospholipase A2 (PLA2) from rheumatoid synovial fluid was studied using two different assays. Human and bovine serum albumins increased the rate of PLA2 hydrolysis of membrane-associated phospholipid substrates. In contrast, albumin profoundly inhibited the PLA2 hydrolysis of synthetic phospholipids in micellar dispersion. Other plasma proteins (alpha, beta and gamma-globulins) had minimal effect on PLA2 activity in either assay system. Since the presence of albumin may compromise estimation of PLA2 and of phospholipase-inhibitory proteins, the appropriate selection of assay conditions is obligatory for the accurate quantitation of their respective activities.

Inflammatory effect of intradermal administration of soluble phospholipase A2 in rabbits

Extracellular phospholipase A2 (PLA2) has been found in association with inflamed sites in experimental animals and in humans. The tissue effects of soluble PLA2 have not been defined. We studied the development of inflammatory changes in rabbit skin subsequent to intradermal injection of active and inactivated venom and pancreatic PLA2, over a broad concentration range. PLA2, at concentrations encountered in human disease, caused acute inflammatory changes characterized grossly by erythema and induration, and histologically by inflammatory cell infiltration, vascular and tissue damage, and abscess formation. Extracellular PLA2 may be considered as one of the pathogenic factors in inflammatory reaction.

Persistent cold agglutinins in AIDS and related disorders

Eighty-one homosexual patients positive for HTLV-III antibody, including 19 with AIDS, 20 with chronic lymphadenopathy syndrome, 10 with AIDS-related complex (ARC) and 32 symptom-free individuals were assessed for the presence of cold agglutinins (CA). In 12 cases, CA were found; 4, 4, 2 and 2, respectively, in each of the above mentioned groups. Seven anti-I, 4 anti-i and 1 anti-Gd CA were identified. In 11 of 12 patients, CA were persistent. There were no differences between CA-negative and CA-positive patients with regard to the presence of other antibodies, anemia, frequency of intercurrent infections or development of lymphoproliferative neoplasia. It can be concluded that persistent synthesis of CA may be associated with the HTLV-III infection.

Phospholipase A2 activity in sera and synovial fluids in rheumatoid arthritis and osteoarthritis. Its possible role as a proinflammatory enzyme

Phospholipase A2 (PLA2) activity was found in the sera and synovial fluids (SF) in rheumatoid arthritis (RA) and osteoarthritis (OA). PLA2 activity in RA SF was 6158 +/- 549 (SEM) U/ml (n = 48) and in RA sera 554 +/- 175 U/ml (normal sera-115 +/- 12 U/ml). In OA SF PLA2 activity was 5069 +/- 542 U/ml (n = 28), and in OA sera 268 +/- 55 U/ml. There was no significant difference between SF PLA2 activity in RA and OA. PLA2 activity in SF did not correlate with muramidase (lysozyme), beta-glucuronidase, total protein or white cell count, which were all significantly higher in RA SF than OA. A positive correlation between PLA2 in SF and matched sera was found in both RA and OA. It may be concluded that significant elevation of extracellular PLA2 occurs in both RA and OA, especially in the SF. The fact that high PLA2 did not correlate with other enzymes such as lysozyme and beta-glucuronidase, which are usually high in RA and low in OA SF, may mean that the handling of PLA2 in the joint space is different from other enzymes.

The effect of chemotherapeutic agents on chemotaxis and random migration of human leukocytes

Chemotherapeutic agents (CTAs) used for treatment of neoplastic and other diseases may influence defense mechanisms of the patient, altering various humoral and cellular immunologic functions. Herein we report the influence of 16 CTAs on random migration and chemotaxis of human polymorphonuclear cells (PMNCs), using two methods, under-agarose migration and double-filter Boyden chambers with 51Cr-PMNCs. Random migration was inhibited by vinblastine only (P less than .01). BCNU and daunorubicin inhibited random migration only when used in high concentrations. In under-agarose migration, only BCNU and vinblastine inhibited chemotaxis (P less than .01) in therapeutic concentrations. Inhibition was also observed when higher concentrations of vincristine were tested. In the Boyden method, marked inhibition of chemotaxis (P less than .01) was caused by BCNU, vinblastine, vincristine, daunorubicin, and doxorubicin. Inhibition of chemotaxis could not be reversed by washing the cells after preincubation. CTAs per se did not have chemoattractant activity. This study shows that some chemotherapeutic agents inhibit random and directed migration of human PMNCs. It also supports the evidence that Boyden chamber method may detect chemotactic abnormalities that escape recognition by the under-agarose migration method. Suppression of locomotion of PMNCs should be taken into consideration in patients treated with CTAs.

Characterization of extracellular phospholipase A2 in rheumatoid synovial fluid

Phospholipase A2 (PLA2) activity has now been identified in rheumatoid synovial fluids. This PLA2 is a calcium-requiring protein of MW 11,000 with a neutral pH optimum. Its activity was inhibited by high concentrations of Mg2+, and by the active site-directed histidine reagent p-bromophenacyl bromide. Ionic and nonionic detergents, or the sulfhydryl reagent dithiothreitol caused loss of enzyme activity. Synovial fluid PLA2 did not interact with sulphated mucopolysaccharides such as heparin or chondroitin sulphate. Release and sequestration of PLA2 in the joint space may contribute to the characteristic rheumatoid inflammatory changes.

Fulminant gangrene in transient cold agglutinemia associated with Escherichia coli infection

Fulminant gangrene of the fingers, toes and nose developed in a 57-year-old woman with Escherichia coli pneumonia. Cryoglobulinemia was noted, and the cryoglobulin was identified as IgM-IgG with anti-I cold agglutinin activity. The cold agglutinins possessed potent lymphocytotoxic and monocytotoxic activity and weaker granulocytotoxic activity. Treatment with plasmapheresis, steroids and antibiotics led to complete clinical recovery, although amputation of several toes was necessary. The patient died 1 1/2 years later; the main findings at autopsy were chronic and acute pyelonephritis and acute bacterial endocarditis. This seems to be the first case of IgM-IgG cold agglutinemia occurring during the course of E. coli infection and the third case of fulminant gangrene complicating transient cold agglutinemia.

Lymphocytotoxic activity of monoclonal immunoglobulins in plasmalymphocytic diseases

95 of 1,019 (9.3%) sera with monoclonal immunoglobulins (MIg) were found to have cold-reacting lymphocytotoxins (LCT). There was no difference in the prevalence of LCT in multiple myeloma, macroglobulinemia, cancer, lymphoma or benign monoclonal gammopathy. Prevalence of LCT was similar in various classes and types of MIg with the exception of the IgG/lambda group in which LCT were more common than in IgG/K (p = 0.013). IgMs had the most potent whereas IgAs had the weakest LCT activity. MIg were purified from 61 LCT-positive sera. 25 pure MIg (41%) had LCT activity. In the rest, LCT activity resided in other fractions. 64 sera with LCT were tested against B and T cells; 56% were equally cytotoxic to B and T cells, 39% killed more B cells and 5% killed more T cells. 18 purified lymphocytotoxic MIg killed both B and T cells. When serial dilutions of sera, and of purified MIg were tested, in all but one instance the reactivity with the T cells weakened more than that with the B cells. Lymphocytotoxins absorbed to and eluted from the peripheral blood lymphocytes or separately from B or from T cells retained LCT activity against B and T lymphocytes. It may be concluded that about one tenth of sera with M components have lymphocytotoxic activity and that in about 40% of these positive sera, this activity is related to the monoclonal immunoglobulins. LCT react with both B and T cells. Antilymphocyte activity of MIgs may play a role in immunoregulatory abnormalities in plasmalymphocytic diseases.

Modulation of phagocytosis and intracellular bactericidal activity of polymorphonuclear and mononuclear cells by cationic proteins from human granulocytes: alternative pathway of phagocytic enhancement

Cationic lysosomal proteins from human polymorphonuclears (PMN) were isolated by column chromatography and divided into five fractions. On acrylamide gel electrophoresis, fraction I had four bands slower than lysozyme (LZM) mobility; fraction II had five or six bands slower than LZM; fraction III had at least seven bands slower and two bands faster than LZM; fraction IV contained LZM, two bands faster and a few faint bands slower than LZM; fraction V was composed of almost pure LZM. Partial characterization of the fractions showed presence of neutral protease in fractions I-IV, chymotrypsin in fraction III, lysozyme in fractions IV and V, and phospholipase A2 mainly in fractions II and III. Modulatory activity of fractions I-V were tested at concentrations up to 50 micrograms/ml. Enhancement of phagocytosis of Staphylococcus aureus was observed by fractions I, IV, and V, whereas phagocytic index was enhanced by all but the fraction II. Intracellular bactericidal activity (ICBA) was markedly enhanced by fractions I, II, and V. Addition of DNA or cytochalasine B inhibited or abolished phagocytosis-enhancing activity of cationic fractions. Their influence on ICBA was much less pronounced. Fraction III enhanced phagocytic index and phagocytosis of E. coli, whereas fractions I and II enhanced intracellular bactericidal activity against this bacteria. Enhancement of phagocytic activity of monocytes has also been observed. The data suggest that some cationic lysosomal fractions from human PMNs enhance phagocytosis and phagocytic index by human PMNs and monocytes and intracellular bactericidal activity of human PMNs. This alternative pathway of phagocytic enhancement is unrelated to the previously described enhancers of phagocytosis and may play a role in defense mechanisms against infection.