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In vivo neutrophil emigration in response to interleukin-1 and tumor necrosis factor-alpha
1Department of Pathology, School of Medicine, University of New Mexico, Albuquerque.
Abstract:
The migration of polymorphonuclear leukocytes (PMN) in response to recombinant interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF), C5a, and f-met-leu-phe-lys (FMLPL) in vivo was studied using a mouse subcutaneous sponge implantation model. In this model sponges were implanted in C3H/OUJ mice, and 2 days later they were injected with the test sample. After varying times, sponges were removed and digested with collagenase, and total cell counts and differentials were enumerated. IL-1 was found to stimulate a significant influx of PMN, which peaked at 6 hr and declined to near baseline levels by 24 hr. This response was dose-dependent, with the greatest response observed when 5 units of IL-1 were injected. When the IL-1 concentration was increased to 10 U, the total number of PMN migrating into the sponge was decreased, compared with that observed with 5 U of IL-1. The overall number of PMN migrating into the sponge 6 hr after injecting 5 U of IL-1 averaged 269% of the number of PMN migrating randomly into the sponge. No difference in the total number of macrophages or lymphocytes in control or IL-1-injected sponges was observed in this time frame. Heat treatment of the IL-1 at 90 degrees C for 30 min ablated the response. Similar studies with TNF and C5a showed that both of these agents also stimulated an influx of PMN that peaked 6 hr postinjection. In contrast, FMLPL did not stimulate a PMN response. When IL-1 and TNF were injected simultaneously, an additive response was observed. These data indicate that IL-1, TNF, and C5a can all stimulate a PMN response in vivo and support the hypothesis that these substances are actively involved in the mobilization of PMN to inflammatory sites in vivo.
Insights
Interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF), and C5a stimulate polymorphonuclear leukocyte (PMN) migration in vivo. These inflammatory mediators are crucial for mobilizing PMNs to sites of inflammation.
Area of Science:
- Immunology
- Inflammation Research
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMNs) are critical immune cells involved in inflammatory responses.
- Understanding the in vivo regulation of PMN migration is essential for developing anti-inflammatory therapies.
Purpose of the Study:
- To investigate the in vivo effects of interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF), C5a, and f-met-leu-phe-lys (FMLPL) on PMN migration.
- To elucidate the role of these mediators in inflammatory site mobilization.
Main Methods:
- A mouse subcutaneous sponge implantation model was utilized.
- Sponges were implanted, injected with test samples (IL-1, TNF, C5a, FMLPL), and retrieved at various time points.
- Cellular content, including PMNs, macrophages, and lymphocytes, was analyzed after collagenase digestion.
Main Results:
- IL-1 significantly stimulated PMN influx, peaking at 6 hours in a dose-dependent manner (optimal at 5 units).
- TNF and C5a also induced PMN migration, with peak responses at 6 hours postinjection.
- FMLPL did not elicit a PMN response, while simultaneous IL-1 and TNF injection showed an additive effect. Heat-inactivated IL-1 lost its stimulatory capacity.
Conclusions:
- IL-1, TNF, and C5a are potent stimulators of in vivo PMN migration.
- These findings support the hypothesis that IL-1, TNF, and C5a actively contribute to PMN mobilization at inflammatory sites.