The ability of the human immunodeficiency virus type 1 (mHV-1) to replicate in primary blood dendritic cells was investigated. Dendritic cells compose <1% of the circulating leukocytes and are nondividing cells. Highly purified preparations of dendritic cells were obtained using recent advances in cell fractionation. The results of these experiments show that dendritic cells, in contrast to monocytes and T cells, support the active replication of all strains of HIV-1 tested, including T-cell tropic and monocyte/macrophage tropic isolates. The dendritic cell cultures supported much more virus production than did cultures of primary unseparated T cells, CD4+ T cells, and adherent as well as nonadherent monocytes.

Cultured human mesothelial cells were exposed to peritoneal dialysis fluids, supernatants from cultures of Staphylococcus aureus and S. epidermidis, and antibiotics. Mesothelial cell monolayer cultures were derived from surgically removed omentum. The cytotoxicity of various agents for the cultured mesothelial cells was measured by a 51 Cr-release assay. All brands of fresh peritoneal dialysis fluids induced a more than 50% 51 Cr-release after 18 h. Morphological changes observed included retraction and shrinking of cells, pyknosis of the nuclei and, finally, detachment of cells over an 18-h period. Neutralization of the acid (pH 5.2–5.5) fluids to pH 7.3 did not abolish the cytotoxicity. In contrast, effluent dialysis fluids were not toxic for mesothelial cells; neither was acid (pH 5.5) culture medium nor culture medium with glucose up to 2%. However, higher glucose concentrations induced increasing 51 Cr-release. Furthermore, filter-sterilized supernatants of S. aureus were cytotoxic for mesothelial cell monolayers in 4/7 (57%) strains of S. aureus tested. In contrast, only 4/29 (14%) strains of S. epidermidis produced cytotoxic exoproducts (p = 0.03). Antibiotics were not found to be cytotoxic, with the possible exception of erythromycin. We conclude that currently available peritoneal dialysis fluids are cytotoxic for mesothelial cells in vitro and that during episodes of peritonitis exoproducts of some bacterial strains may further reduce mesothelial cell viability.

The total cell count and cell differentiation of the overnight peritoneal dialysis effluent (PDE) was analysed in 34 long-term CAPD patients. The mean percentage and yield of mesothelial cells were 3.1% and 0.17 × 106 per PDE. There was a significant lower percentage and yield of mesothelial cells in the PDE of patients with a peritonitis incidence (PI) of more than 2 episodes a year. Independent of dwell time, a positive correlation between the total yield of leucocytes and the yield of mesothelial cells was found. No relation between the amount of phospholipids in the PDE and the yield of mesothelial cells could be shown. Mesothelial cells in the PDE are probably reflecting the turn-over rate of a reactive mesothelium. Whether a low turn-over rate of the mesothelium is causing or is caused by a high PI needs further investigation.

The endogenous peroxidatic activity (PA) pattern of peritoneal macrophages from 24 continuous ambulatory peritoneal dialysis (CAPD) patients and from five healthy women undergoing laparoscopy was studied. In general, the macrophages showed two different PA patterns in vivo: exudate and negative macrophages. However, two of 24 CAPD patients showed resident macrophages, the first described in vivo in man. Since, in general, the examined human peritoneal macrophages are exudate and PA-negative, this suggests, in accordance with the animal model system, that a chronic sterile inflammation exists in the peritoneal cavity of CAPD patients and healthy women undergoing laparoscopy. After 2 hr culture, blood monocytes and peritoneal macrophages transformed into cells with the characteristics of exudate-resident and resident macrophages, so isolation procedures that include short periods of culture can change the developmental stage of human monocytes and macrophages.

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