The supernatant fluid of axenically grown E. histolytica inhibits chemotaxis, chemokinesis and random mobility of human mononuclear phagocytes (MP) as measured in Boyden chambers. Human polymorphonuclear phagocytes (PMN) locomotion is apparently unaffected. The factor was found in comparable amounts in the supernatant fluid of axenic cultures of four E. histolytica strains that differed in their human pathogenicity and virulence, as well as in two entamoebas non-pathogenic for man. This dialysable and thermolabile MP-locomotion inhibiting entamoeba product (EP) can be absorbed out by incubation with MP, but not with lymphocytes, while partial absorption was observed using PMN. The MP-locomotion inhibitory effect of this EP was cancelled by inhibiting protein synthesis in the MP by means of cycloheximide. In vivo, this EP caused a delay in MP migration in Rebuck skin windows. The molecular weight of this EP lies between 478 and 765 by gel-sieve chromatography. Our results suggest a direct effect upon the cytoskeletal and locomotive apparatus of the MP. This MP-locomotion inhibiting EP could contribute to the paucity of the inflammatory reaction observed in the advanced stages of invasive amoebiasis and consequently also to the lack of scar tissue formation upon healing of amoebic lesions.
The bactericidal capacity of mononuclear and polymorphonuclear phagocytes obtained from normal newborn infants and from healthy adults was evaluated in vitro, using two group B beta-hemolytic streptococci (GBBHS) serotypes (GBBHS-Ia-SS-615/28 and GBBHS-III-SS-620/50) and uniform opsonic conditions. No intertype differences in bacteriolysis of these two serotypes were observed among leukocytes from newborns or adults. As group, only polymorphonuclear phagocytes from newborns disclosed a significantly lower mean bactericidal capacity than their adult cellular counterpart, and only with respect to GBBHS-III-SS-620/50. On the other hand, 4 or 16 polymorphonuclear samples from newborns tested revealed significantly low bactericidal capacities against both GBBHS serotypes, and an additional sample revealed a bactericidal capacity against GBBHS-III-SS-620/50 alone. Interstrain variations in the intrinsic bactericidal capacity of polymorphonuclear phagocytes from newborns against GBBHS-III may exist, as suggested by a single observation made by using four clinical isolates of GBBHS-III. Such deviant phagocytic capacities of polymorphonuclear phagocytes from newborns may constitute an additional selective risk factor in the genesis of GBBHS sepsis of the newborn.
SummaryUnder-agarose random migration, chemokinesis and chemotaxis of monocytes from 36 patients with Down's syndrome were compared to those of monocytes from 42 healthy, age-matched control children. Random migration of monocytes from patients with Down's syndrome was comparable to that of controls. In contrast, chemotaxis of monocytes from patients with Down's syndrome was significantly decreased (P < 0.001) when com~ared to that of controis, even though chemokinesis was significantly increased (P < 0.001). Age, sex, and physical development of patients with Down's syndrome or of control children included in this study had no apparent effect upon monocyte mobility. Abbreviations CS, control serum DS, Down's syndrome MP, mononuclear phagocytes ZAS, zymosan-activated serum Increased susceptibility to infection in patients with DS (22,28) may reflect several abnormalities in host defense mechanisms involving humoral and cellular immune responses (2, 17) and the inflammatory-phagocytic process (13,15,27). No defect can be singled out as the most important one, hence the definition of the immunodeficiency of DS as a complex sum of several immunologic faults of variable intensity that can change with age (4). Cellmediated immunity in DS is predominantly impaired at its effector site (34): depressed in vitro lymphocyte responses, anergy or weak delayed type hypersensitivity skin reactions and decrease in circulating T cells have been reported in patients with DS (16,17), although lymphocytosis with high counts of T and B cells may be found in older, institutionalized patients (34).MP and lymphocytes constitute the bulk of the inflammatory cells in delayed hypersensitivity reactions, MP playing a crucial role in phagocytosis as well (5). Accumulation of mononuclear cells at such inflammatory sites depends largely on their response to chemotactic signals. Poor mobilization of these cells may contribute to the weakness of delayed hypersensitivity and other inflammatory reactions in DS (6). We measured random migration, chemokinesis (enhancement of random migration) and chemotaxis (directional migration) of MP from patients with DS and compared them to those of healthy age-matched children. We employed the agarose-plate method (21), which is less expensive, simpler, and more reproducible than the Boyden chamber method, even though the relative sensitivity of the two assays is still somewhat controversial (14,19). Only MP of a mononuclear leukocytes population seem to contribute to the migration pattern using the agarose device (21). MATERIALS AND METHODSPatients and controls. Thirty-six home-cared patients with DS (Trisomy 21: 14 females, 22 males, 6 months to 7 years of age) were studied. None of the patients had leukemia, suffered of overt infection or took any medication within 2 wk of the study. Fortytwo healthy children (15 females, 27 males, 6 months to 7 years of age) undergoing elective orthopaedic surgery, and matched as closely as possible with the patients for similar age and sex were used as controls. Differe...
Unlike normal (i.e., non-activated) human eosinophils that are unable to destroy virulent Entamoeba histolytica even in the presence of antibodies and complement, activated eosinophils effectively destroy the parasite in vitro without the help of opsonins, yet increase this capacity with their assistance. Many activated eosinophils succumb in the process as well, probably victims of toxic products released by dying amoebae. Human activated eosinophils thus behave more like activated macrophages than like neutrophil polymorphonuclear leucocytes that are notoriously incompetent in dealing with virulent amoebae. As a regular constituent of early inflammatory reactions, and notwithstanding the absence of blood and tissue eosinophilia in invasive amoebiasis, the activated eosinophil may play a role in the defence against E. histolytica.
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