Host and Bacterial Factors Involved in the Innate Ability of Mouse Macrophages To Eliminate Internalized UnopsonizedEscherichia coli

Abstract

In an effort to better understand genetic and cellular factors that influence innate immunity, we examined host and bacterial factors involved in the nonopsonic phagocytosis and killing of Escherichia coli K-12 by mouse macrophages. Unelicited (resident) peritoneal macrophages from five different mouse strains, BALB/c, C57BL/6, CD-1, C3H/HeJ, and C3H/HeN, were employed. Additional macrophage populations were obtained from CD-1 mice (bone marrow-derived macrophages). Also, for BALB/c and C57BL/6 mice, peritoneal macrophages elicited with either thioglycolate or proteose peptone, bone marrow-derived macrophages, and macrophage-like cell lines derived from the two strains were employed. Two E. coli K-12 strains that differed specifically in their abilities to produce type 1 pili containing the adhesive protein FimH were examined. The parameters used to assess macrophage bacteriocidal activity were (i) the killing of internalized (gentamicinprotected) E. coli during the approximately 4-h assay and (ii) the initial rate at which internalized E. coli were eliminated. Data on these parameters allowed the following conclusions: (i) unelicited or proteose peptoneelicited peritoneal macrophages were significantly better at eliminating internalized bacteria than thioglycolate-elicited peritoneal macrophages, bone marrow-derived macrophages, or macrophage cell lines; (ii) the host genetic background had no significant effect upon the ability of unelicited peritoneal macrophages to kill E. coli (even though the mouse strains differ widely in their in vivo susceptibilities to bacterial infection); and (iii) the FimH phenotype had no significant effect upon E. coli survival once the bacterium was inside a macrophage. Additionally, there was no correlation between the bacteriocidal effectiveness of a macrophage population and the number of bacteria bound per macrophage. However, macrophage populations that were the least bacteriocidal tended to bind higher ratios of FimH ؉ to FimH ؊ E. coli. The effect of gamma interferon, fetal calf serum, and the recombination proficiency of E. coli were examined as factors predicted to influence intracellular bacterial killing. These had no effect upon the rate of E. coli elimination by unelicited peritoneal macrophages.

Role of the phagosomal redox-sensitive TRP channel TRPM2 in regulating bactericidal activity of macrophages

“…Bactericidal activity of macrophage was analyzed by performing a colonyforming unit (CFU) assay as described previously (Hamrick et al, 2000). Pseudomonas aeruginosa strain 103 (PA) and Staphylococcus aureus strain USA 300 (SA) were grown in tryptic soy broth for 14 h at 37°C, and bacteria concentrations were determined by serial dilutions and counting CFUs.…”

Association between macrophage activation and function of micro-encapsulated rat islets

“…For transplantation experiments, total islet volume was at least 10 µl, which is approximately equal to the endocrine volume of the normal rat pancreas [19]. grown capsules, from peripheral blood, or (proteose-peptone elicited) peritoneal macrophages [29]. This was done by comparing the number of iNOS-positive macrophages obtained from the in vitro-system with those collected in vivo on capsules directly fixed after being flushed from the peritoneal cavity.…”

Synaptotagmin XI Regulates Phagocytosis and Cytokine Secretion in Macrophages

“…Infections were carried out according to the protocol outlined by Hamrick et al (41). Bacteria were added in 20 ml PBS, and plates were centrifuged at 1000 3 g for 1 min.…”