title: Conditioned medium from activated rat macrophages and the recombinant factors, IL-1 beta and GM-CSF, enhance the accessory activity of dendritic cells.
abstract: Low density lymph node cells (LD-LNC; 5% of total unfractionated LNC) contain 95% of the accessory activity required for responses of T lymphocytes to mitogens. Significantly greater responses to mitogens occur when T lymphocytes are added to LD-LNC that have been exposed overnight to silica, in comparison to responses occurring with LD-LNC incubated without silica. Conditioned medium (CM) from silica-treated LD-LNC is itself able to mediate enhanced responses; i.e., when LD-LNC are exposed overnight to CM alone and mitogen-treated T lymphocytes added the next day. The enhancing activity found in CM from LD-LNC exposed to silica is produced by macrophages; however, their low accessory activity is not enhanced by CM. In contrast, dendritic cells isolated from LD-LNC exposed to silica or to CM show significantly increased accessory activity, but dendritic cells do not produce the enhancing activity found in CM. CM lacks IL-2 activity and does not have any effect on the responses of untreated or mitogen-treated T lymphocytes alone. Thus, macrophages produce the enhancing activity and dendritic cells respond to it. Maximum enhancement of dendritic cell accessory activity requires overnight exposure to CM; once induced, accessory activity is not further modulated after continued incubation in the presence or absence of CM. LD-LNC, adherent peritoneal exudate cells, and adherent thioglycollate-induced peritoneal exudate cells produce enhancing activity after exposure to silica, LPS, and silica plus LPS. After gel filtration of a CM produced by silica plus LPS, enhancing activity shows a broad molecular weight distribution between 20 and 55 kD. IL-1 is present in CM and shows a more narrow molecular weight distribution that falls within the lower molecular weight range for enhancing activity. Silica treatment by itself produces CM containing little IL-1, but abundant enhancing activity; gel filtration of this CM shows that the distribution of enhancing activity is confined more narrowly to the higher molecular weight range, suggesting that IL-1 is one of several factors that enhances the accessory activity of dendritic cells. Recombinant human IL-1 beta does have enhancing activity, but of the other recombinant factors tested only mouse GM-CSF also has enhancing activity. Human IL-1 alpha, tumor necrosis factor alpha, IL-4, rat IL-3 and rat IFN-gamma, as well as L cell-conditioned medium containing M-CSF, lack enhancing activity.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of South Carolina, Columbia.
authors.forename: W E
authors.initials: WE
authors.lastname: Bowers
authors.forename: M S
authors.initials: MS
authors.lastname: Ruhoff
authors.forename: E M
authors.initials: EM
authors.lastname: Goodell
mesh_terms: D000818:Animals; D001685:Biological Factors / Q000302:isolation & purification; D002850:Chromatography, Gel; D003115:Colony-Stimulating Factors / Q000502:physiology*; D003470:Culture Media / Q000032:analysis; D003713:Dendritic Cells / Q000276:immunology*; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000502:physiology*; D007375:Interleukin-1 / Q000502:physiology*; D008262:Macrophage Activation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000494:pharmacology; D012822:Silicon Dioxide / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
chemical_list: D001685:Biological Factors; D003115:Colony-Stimulating Factors; D003470:Culture Media; D006133:Growth Substances; D007375:Interleukin-1; D011994:Recombinant Proteins; D014316:Tritium; D012822:Silicon Dioxide; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013936:Thymidine