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Induction of human gamma interferon by protein A from Staphylococcus aureus
Abstract:
Protein A from Staphylococcus aureus (SpA) has been observed to stimulate the production of human gamma interferon (HuIFN gamma) by peripheral blood mononuclear cells (MNC). Dose-dependent experiments showed donor-to-donor variation in the concentration of SpA required for maximum IFN production although 50 micrograms/ml consistently produced near peak IFN gamma titers for each donor. Kinetic studies revealed that peak IFN gamma production occurred 24 hr after SpA stimulation. Physicochemical and antigenic characterization showed that SpA-induced IFN possessed the characteristics of IFN gamma in that it was inactivated by treatment at pH 2, heating at 56 C and anti-HuIFN gamma serum but not by anti-HuIFN alpha serum. Further studies showed tha maximum IFN gamma production could be achieved by stimulating 5 x 10(6) MNC/ml and IFN gamma could be harvested for 3 successive days by removing IFN gamma-containing supernatant fluids and adding fresh medium to stimulated MNC cultures. Preliminary cell fractionation studies suggest that the mononuclear cell that produces IFN gamma after SpA stimulation is a nonadherent lymphocyte that lacks high affinity receptors for sheep erythrocytes and expresses Fc receptors for IgG. Moreover, unlike other mitogen inducers, SpA appears to be less dependent on the presence of macrophages for IFN gamma production.
Insights
Staphylococcus aureus Protein A (SpA) stimulates human gamma interferon (HuIFNγ) production by peripheral blood mononuclear cells (MNCs). This study characterizes SpA-induced HuIFNγ, identifying lymphocyte subsets responsible for its production.
Area of Science:
- Immunology
- Microbiology
Background:
- Protein A from Staphylococcus aureus (SpA) is known to activate immune cells.
- The induction of human gamma interferon (HuIFNγ) by SpA in peripheral blood mononuclear cells (MNCs) has been observed.
Purpose of the Study:
- To characterize the physicochemical and antigenic properties of SpA-induced HuIFNγ.
- To identify the specific cell types within MNCs responsible for HuIFNγ production upon SpA stimulation.
- To determine optimal conditions for SpA-induced HuIFNγ production.
Main Methods:
- Dose-response and kinetic studies were performed using varying concentrations of SpA and MNCs.
- Physicochemical treatments (pH 2, 56°C) and antiserum neutralization (anti-HuIFNγ, anti-HuIFNα) were used for characterization.
- Cell fractionation techniques were employed to identify the producing cell populations.
Main Results:
- SpA consistently stimulated HuIFNγ production in MNCs, with peak levels at 24 hours post-stimulation.
- SpA-induced IFN exhibited characteristics of HuIFNγ, being inactivated by low pH, heat, and anti-HuIFNγ serum.
- Optimal production was achieved with 5 x 10^6 MNCs/ml, and IFNγ could be harvested for three consecutive days.
- Preliminary studies indicated that nonadherent lymphocytes lacking sheep erythrocyte receptors but expressing Fc receptors for IgG are the primary producers.
- SpA-induced HuIFNγ production showed less dependence on macrophages compared to other mitogens.
Conclusions:
- SpA is an effective stimulator of HuIFNγ production by MNCs.
- The characterized HuIFNγ is biologically and antigenically distinct from HuIFNα.
- SpA-induced HuIFNγ production involves specific lymphocyte subsets and is relatively macrophage-independent.