THE EFFICIENT BOVINE INSULIN PRESENTATION CAPACITY OF BONE-MARROW-DERIVED MACROPHAGES ACTIVATED BY GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR CORRELATES WITH A HIGH-LEVEL OF INTRACELLULAR REDUCING THIOLS

Bone marrow-derived macrophages (BMMPHI) were shown before to function as antigen-presenting cells.We show here, that the antigen presentation capacity of BMMPHI depends on the nature of the antigen and is differently regulated by the lymphokines interferon-gamma (IFN-gamma) and granulocyte/macrophage-colony-stimulating factor (GM-CSF). When bovine insulin (BI) was employed as antigen, only BMMPHI treated with GM-CSF (GM-CSF-MPHI) were efficient presenters, but when presentation of the antigens ovalbumin and conalbumin was tested, IFN-gamma-pulsed BMMPHI (IFN-gamma-MPHI) proved superior to GM-CSF-MPHI. The lack of efficient BI presentation function of IFN-gamma-MPHI was only obvious, when native BI was used as antigen. Preprocessed BI was presented by IFN-gamma-MPHI with drastically higher efficiency than by GM-CSF-MPHI. Because processing of insulin depends on reduction of disulfide bonds, we analyzed the content of intracellular reducing thiols within IFN-gamma-MPHI, GM-CSF-MPHI, and untreated BMMPHI. Only after stimulation with GM-CSF did the amount of reduced glutathione and cysteine strongly increase, while IFN-gamma did not efficiently augment the intracellular content of both thiols. These findings suggest that the lymphokines IFN-gamma and GM-CSF differently interfere with the processing capacity of BMMPHI by differently regulating the intracellular concentration of the thiols reduced glutathione and cysteine. A high level of these thiols induced by GM-CSF correlates with a prominent capacity to present the antigen bovine insulin.