The expression of I-A correlates with the uptake of interferon-gamma by macrophages.
The current studies were designed to examine some of the requirements for I-A expression when macrophages (M phi) were treated with interferon-gamma (IFN-gamma). In order to define the minimum time required for IFN-gamma to induce surface expression of I-A antigen on bone marrow-derived M phi, cells were incubated with IFN-gamma for varying lengths of time, washed and thereafter incubated for 72 h before assaying I-A surface expression. Using saturating amounts of IFN-gamma (300 IRU/ml), we found that between 0 and 30 min of IFN-gamma treatment there is a direct correlation between the length of treatment and the level of I-A surface expression. When the steady state level of RNA for the I-A beta gene was assayed, a low level of I-A beta RNA was seen in cells treated for 10 min with saturating amounts of IFN-gamma (300 IRU/ml) while a 30-min or 60-min exposure of cells to the same concentration of IFN-gamma resulted in a steady increase in the level of I-A beta RNA. Similar results were found when we measured the levels of RNA for the tumor necrosis factor and C3 complement genes, both of which are induced by IFN-gamma in M phi. M phi treated with low amounts of IFN-gamma (3 IRU/ml) for 30 min do not express cell surface I-A. Cells incubated continuously for 72 h with 3 IRU/ml of IFN-gamma expressed a level of I-A on the surface equivalent to the level of I-A expressed on cells treated for only 30 min with 300 IRU/ml of IFN-gamma. Based on the observed correlation between either the IFN-gamma concentration or the length of time the cells were exposed to IFN-gamma, or the level of I-A expression on M phi, we conclude that the expression of I-A correlates with the uptake of IFN-gamma.
Celada
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La Jolla Cancer Research Foundation, CA 92037.
Maki
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RA
D000818:Animals; D003176:Complement C3 / Q000235:genetics / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000032:analysis* / Q000235:genetics; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008811:Mice, Inbred DBA; D012335:RNA, Ribosomal / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
D003176:Complement C3; D000949:Histocompatibility Antigens Class II; D012335:RNA, Ribosomal; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma