title: Mast cells retain their responsiveness upon continuous and repetitive exposure to antigen.
abstract: To assess the effects of prolonged and repetitive exposure of antigen on mast cells (MC) we utilized our co-culture system in which rat peritoneal MC are kept viable and functionally active on 3T3 fibroblasts. MC were presensitized with IgE anti-dinitrophenyl-human serum albumin (anti-DNP-HSA), activated with the relevant antigen (DNP-HSA) (69.4% histamine release) and incubated for 7 days in medium alone or medium containing the antigen with or without Ca2+ ions. During the prolonged incubation MC released only small amounts of histamine (20-26 ng/plate/day) under all the different culture conditions. Moreover, these MC were not activated after each medium replacement with fresh antigen. When activated MC cultured in medium containing antigen and Ca2+ were presensitized prior to a second challenge performed on days 1, 2, 5 and 7, they released 35-45% histamine but were still partially desensitized compared to initially challenged MC. Immunofluorescence studies demonstrated that the MC unresponsiveness to a second challenge could be partially attributed to lack of membrane-associated IgE antibodies. Repetitive activation (four times) of MC at daily intervals did not abrogate their releasing capacity although the intracellular histamine content was diminished. When repetitive activation was performed 2 and 4 hr after the first challenge, a more intense MC refractoriness was observed (release of 17.3% and 21.1% histamine respectively versus 67.7%). It is suggested that MC activation occurs even after continuous exposure to antigen and that MC can respond to repetitive immunological stimulation.
authors.affiliation: Department of Medicine, Hadassah University Hospital, Jerusalem, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Shalit
authors.forename: D
authors.initials: D
authors.lastname: Pickholz
authors.forename: F
authors.initials: F
authors.lastname: Levi-Shaffer
mesh_terms: D000818:Animals; D000941:Antigens / Q000008:administration & dosage*; D002478:Cells, Cultured; D004140:Dinitrophenols / Q000008:administration & dosage / Q000276:immunology; D006636:Histamine Release / Q000276:immunology*; D008407:Mast Cells / Q000276:immunology*; D010529:Peritoneal Cavity / Q000166:cytology; D051381:Rats; D012709:Serum Albumin / Q000008:administration & dosage / Q000276:immunology
chemical_list: D000941:Antigens; D004140:Dinitrophenols; D012709:Serum Albumin; C058064:dinitrophenyl-human serum albumin conjugate