Related Experiment Videos
Fibroblast stimulation in schistosomiasis. V. Egg granuloma macrophages spontaneously secrete a
Abstract:
Isolated intact egg granulomas from the liver of Schistosoma mansoni-infected mice have been previously shown to elaborate factors in vitro that can stimulate fibroblasts for biological functions that are of potential importance in the pathogenesis of hepatic fibrosis in schistosomiasis. We report here that cell cultures obtained from monodispersed granuloma cell suspensions, and specifically enriched for macrophages (95% to 100%) spontaneously elaborated fibroblast proliferation-stimulating activity in vitro. These cells possessed functional and phenotyptic characteristics of activated macrophages. In contrast, control peritoneal macrophages from uninfected mice lacked such phenotypic characteristics, and did not spontaneously elaborate fibrogenic activity in vitro. The granuloma macrophage activity was present, pre-formed within the isolated cells, and was continuously elaborated during 72 hr of incubation. By gel infiltration chromatography (Sephacryl S-200 sf), fibroblast-stimulating activity was identified in two pooled fractions, one with estimated molecular radius (Mr) of 46 kd to 57 kd and the other with Mr of 10 kd to 16 kd. Preparative isoelectric focusing in granular gel of crude macrophage culture supernatants identified peak activity in fractions with pI approximately 5. Two different serine esterase inhibitors had no effect on the ability of crude granuloma macrophage supernatants to stimulate fibroblast proliferation. Whereas crude and chromatographed fractions of granuloma macrophage supernatant were active for fibroblasts, they had minimal or no interleukin 1 (IL 1) activity when tested in a thymocyte proliferation assay. In contrast, resident peritoneal macrophages from the same infected mice spontaneously secreted substantial IL 1 and fibroblast-stimulating activity in vitro. We conclude that egg granuloma macrophages are activated in vivo to secrete fibrogenic molecules functionally distinct from IL 1, which might contribute to the pathogenesis of hepatic fibrosis in schistosomiasis.
Insights
Activated macrophages within Schistosoma mansoni granulomas secrete factors that stimulate fibroblast proliferation. These fibrogenic molecules are distinct from interleukin-1 and may drive hepatic fibrosis in schistosomiasis.
Area of Science:
- Immunology
- Pathology
- Parasitology
Background:
- Schistosoma mansoni infection causes hepatic fibrosis.
- Granulomas in infected livers release factors stimulating fibroblasts.
- The specific cells and molecules involved are not fully understood.
Purpose of the Study:
- To investigate the role of macrophages within Schistosoma mansoni granulomas in hepatic fibrosis.
- To characterize the fibroblast-stimulating activity produced by these macrophages.
- To determine if this activity is related to interleukin-1.
Main Methods:
- Isolation and culture of granuloma macrophages from infected mice.
- Assay of fibroblast proliferation-stimulating activity in macrophage supernatants.
- Gel filtration chromatography and isoelectric focusing to characterize the active molecules.
- Testing for interleukin-1 activity using a thymocyte proliferation assay.
Main Results:
- Activated macrophages from granulomas spontaneously produced fibroblast proliferation-stimulating activity.
- This activity was characterized by two molecular weight fractions (46-57 kDa and 10-16 kDa) and a pI of approximately 5.
- The activity was not inhibited by serine esterase inhibitors.
- Granuloma macrophage supernatants showed minimal interleukin-1 activity, unlike peritoneal macrophages.
Conclusions:
- Egg granuloma macrophages are activated in vivo during Schistosoma mansoni infection.
- These activated macrophages secrete fibrogenic molecules distinct from interleukin-1.
- These distinct molecules likely contribute to the pathogenesis of hepatic fibrosis in schistosomiasis.