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Human fetal islet response to interferon gamma
B Ruhland1, L Walker, C M Peterson
1Sansum Medical Research Foundation, Santa Barbara, CA 93105.
Insights
Interferon gamma exposure increases immune markers on human fetal islets, potentially linking to diabetes development. This immune response affects insulin secretion and islet cell function.
Area of Science:
- Immunology
- Endocrinology
- Developmental Biology
Background:
- Human fetal islets are crucial for insulin production.
- Understanding islet immune responses is key to diabetes research.
- Interferon gamma (IFN) is a cytokine with immunomodulatory effects.
Purpose of the Study:
- To investigate the effect of IFN on human fetal islet cells.
- To assess changes in major histocompatibility complex (MHC) expression.
- To evaluate the impact on insulin secretion and immune cell response.
Main Methods:
- In vitro exposure of human fetal islets to Interferon Gamma (IFN).
- Flow cytometry to analyze MHC class I (HLA-ABC) and class II (HLA-DR) expression.
- Quantification of insulin content and secretion.
- Assessment of autologous mixed islet lymphocyte response.
Main Results:
- IFN significantly upregulated both MHC class I and class II expression on fetal islets.
- A small percentage of IFN-exposed islet cells expressed HLA-DR and contained insulin.
- IFN-exposed DR-positive cells had lower insulin content but retained stimulated secretion capacity.
- Autologous splenocytes showed increased proliferation in response to IFN-treated islet cells.
Conclusions:
- IFN exposure alters human fetal islet immunophenotype and function.
- These IFN-induced changes may contribute to immune-mediated processes in diabetes.
- Pharmacological induction of IFN in fetal islets could initiate pathways predisposing to diabetes.
Abstract:
Investigation was made of the ability of human fetal islets to express major histocompatibility complex class I and class II gene products after in vitro exposure to 1,000 U/ml Interferon Gamma (IFN) for 48 hours as well as the effect of such exposure on insulin secretion and autologous mixed islet lymphocyte response. Flow cytometry analysis revealed that the mean fluorescence activity of both HLA-ABC (class I) and HLA-DR (class II) was significantly (p < 0.01) increased vs the control after IFN incubation. (class I: Control = 125 +/- 35 SD, IFN = 995 +/- 418 S.D.; class II: Control = 70 +/- 30 SD, IFN = 300 +/- 74 S.D.). Cells containing surface expression of DR and intracellular insulin by flow cytometry following depletion of phagocytic cells were also quantified and increased from 0 to 0.67 percent following exposure to IFN. Autologous splenocytes responded to cells previously incubated with IFN with a three fold increase in 3H-thymidine uptake. Interferon gamma exposed, DR positive insulin containing cells contained one third the insulin of DR negative insulin containing cells (2.1 +/- 1.5 vs 6.6 +/- 3.4 microU/cell) but were nevertheless capable of stimulated insulin secretion. Thus, pharmacologic events leading to increased fetal pancreatic interferon concentrations initiate both immune and nonimmune processes that may predispose susceptible individuals to diabetes.