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Published on: April 29, 2015
Secretion of bioactive interleukin 1 by rat testicular macrophages in vitro
R Hayes1, S A Chalmers, D J Nikolic-Paterson
1Institute of Reproduction and Development, Monash University, Clayton, Victoria, Australia.
Insights
Testicular macrophages secrete significantly less interleukin-1 (IL-1) than peritoneal macrophages when exposed to lipopolysaccharide (LPS). This suggests an altered immune response capacity within the testis.
Area of Science:
- Immunology
- Reproductive Biology
- Cell Biology
Background:
- Macrophages are key immune cells involved in inflammation.
- Testicular macrophages reside within the testes and play a role in immune surveillance.
- Peritoneal macrophages are found in the abdominal cavity and are well-characterized immune cells.
Purpose of the Study:
- To compare the pro-inflammatory cytokine interleukin-1 (IL-1) secretion capacity of testicular macrophages versus peritoneal macrophages in response to bacterial lipopolysaccharide (LPS).
- To investigate the potential for altered immune responses within the testis.
Main Methods:
- Isolation of testicular and peritoneal macrophages from adult male rats.
- In vitro culture of macrophages with or without LPS stimulation.
- Measurement of bioactive IL-1 production using a thymocyte proliferation bioassay.
- Confirmation of IL-1 production using a human recombinant IL-1 receptor antagonist.
Main Results:
- Testicular macrophages secreted only 2.8% of the IL-1 produced by peritoneal macrophages under identical LPS stimulation.
- Bioactive IL-1 production was confirmed, and an endogenous inhibitor did not account for the observed differences.
- Testosterone did not affect IL-1 production in peritoneal cells.
Conclusions:
- Testicular macrophages exhibit a markedly reduced capacity to secrete bioactive IL-1 compared to peritoneal macrophages.
- These findings support the concept of an intrinsically altered immune response profile within the testicular microenvironment.
Abstract:
The relative capacities for testicular macrophages and resident peritoneal macrophages to secrete the pro-inflammatory cytokine, interleukin 1 (LL-1), in response to stimulation by bacterial lipopolysaccharide (LPS), were compared in vitro. Macrophages were isolated from adult male rat testicular interstitial cells or peritoneal lavage by adherence to glass coverslips or plastic culture dishes. The macrophages were immediately cultured, with or without a maximal dose of LPS (1 mu g/ml), over 24 hours at 32 degrees Celsius. Bioactive LL-1 production was measured by a sensitive thymocyte proliferation bioassay, employing recombinant human LL-1 beta as the reference standard. In comparison with the peritoneal macrophages, testicular macrophages displayed only a very small response to LPS, producing 2.8% of the amount of LL-1 per cell secreted by peritoneal macrophages cultured under identical conditions. Production of authentic LL-1 was confirmed by inhibition of the bioassay response in the presence of human recombinant LL-1 receptor antagonist. A small molecular mass (<10 kDa based on ultrafiltration) inhibitor of LL-1 bioactivity was also present in the medium collected from both cultures, but this inhibitory activity did not account for the differences in activity observed. In cultures of total peritoneal cells under similar conditions, addition of testosterone (10-1,000 ng/ml) did not affect LL-1 production in response to LPS. These data indicate that testicular macrophages have a reduced ability to secrete bioactive IL-1, and they provide further evidence for an altered capacity for immune responses within the testis.
