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Release of tumor necrosis factor-alpha by human peritoneal macrophages in vivo and in vitro
1Department of Obstetrics and Gynecology, University of California, Los Angeles.
Abstract:
Tumor necrosis factor is a product of activated monocytes, macrophages, and lymphocytes that exerts a variety of effects in the host. Its cytotoxicity toward gametes has been suggested as a mechanism of how activated macrophages may cause subfertility, inasmuch as detectable levels of tumor necrosis factor have been reported in the peritoneal fluid of infertile patients. To further examine this issue we measured tumor necrosis factor activity in peritoneal fluid and its release in vitro from monocytes or peritoneal macrophages of patients undergoing laparoscopy because of either tubal ligation or infertility. Cytolytic activity was determined with a bioassay with sensitized mouse fibrosarcoma cells as target. Significant tumor necrosis factor activity (greater than 5 U/ml) was detected in 38% of the peritoneal fluid samples. A total of 43% of the peritoneal macrophage samples released significant tumor necrosis factor activity in vitro and all samples tested including peripheral monocytes released high levels of activity in the presence of bacterial endotoxin. The activity was released in vitro in a time-dependent manner. Thermal stability characteristics and neutralization with a specific antibody indicated that most of the activity in peritoneal fluid or released in vitro was that of tumor necrosis factor-alpha. Statistical analysis of tumor necrosis factor activity in peritoneal fluid in various diagnostic categories revealed a significantly elevated level in patients with endometriosis, as compared with fertile women. Endometriosis and pelvic adhesions were also significantly more likely to be associated with measurable levels of tumor necrosis factor activity released by peritoneal macrophages in vitro. Overall, because tumor necrosis factor-alpha levels were frequently detectable, it suggests that activation of peritoneal macrophages either by bacterial products or inflammatory conditions can occur in vivo. Moreover, these cells remain competent to release tumor necrosis factor in vitro.
Insights
Tumor necrosis factor-alpha, a key inflammatory cytokine, was frequently detected in infertile patients, particularly those with endometriosis. This suggests activated macrophages contribute to infertility by releasing this factor in the peritoneal cavity.
Area of Science:
- Immunology
- Reproductive Medicine
- Cell Biology
Background:
- Tumor necrosis factor (TNF) is produced by immune cells and can affect host responses.
- Elevated TNF in peritoneal fluid is linked to infertility, potentially via gamete cytotoxicity.
- Activated macrophages are implicated in subfertility mechanisms.
Purpose of the Study:
- To measure TNF activity in peritoneal fluid and its in vitro release from patient monocytes/macrophages.
- To investigate the relationship between TNF levels and infertility, specifically in endometriosis.
- To confirm the identity and characteristics of the detected TNF activity.
Main Methods:
- Collected peritoneal fluid and macrophages from patients undergoing laparoscopy.
- Assayed TNF activity using a bioassay with sensitized mouse fibrosarcoma cells.
- Analyzed TNF-alpha identity via thermal stability and antibody neutralization.
Main Results:
- Significant TNF activity detected in 38% of peritoneal fluid samples.
- 43% of peritoneal macrophages released significant TNF in vitro; all released TNF with endotoxin.
- Elevated peritoneal fluid TNF levels were associated with endometriosis and pelvic adhesions.
Conclusions:
- Peritoneal macrophages are activated in vivo by inflammatory conditions or bacterial products.
- TNF-alpha is frequently detectable in the peritoneal fluid of infertile women, especially those with endometriosis.
- Activated macrophages and TNF-alpha likely play a role in the pathogenesis of infertility.