Interleukin-2 secretion by human B lymphocytes occurs as a late event and requires additional stimulation after CD40 cross-linking.
While Epstein-Barr virus (EBV)-immortalized B cell lines have been shown to secrete interleukin (IL)-2 after stimulation with either teleocidin or phorbol myristate acetate (PMA) and ionomycin, experimental conditions leading to IL-2 production by normal human B cells have not been reported. In the present study we investigated various B cell activating conditions, including--by analogy to EBV-immortalized B lymphocytes--stimulation of B cells that are already proliferating (in cultures with IL-4 and immobilized anti-CD40 monoclonal antibody; the anti-CD40 system). This approach showed that B lymphocytes secreted IL-2 in the culture medium, but only if they were first activated for more than 24 h in the anti-CD40 system before exposure to PMA plus ionomycin. The production rate of IL-2 by B lymphocytes reached a maximum after 6 days of priming in such cultures followed by 48 h of stimulation with PMA plus ionomycin, corresponding to 7% or 15% of that of fresh CD4+ T cells activated, respectively, with phytohemagglutinin plus PMA, or with PMA plus ionomycin for 48 h. This IL-2 production could not be attributed to T cell contamination nor to EBV-infected B cells according to flow cytometric and reverse transcriptase-polymerase chain reaction analysis of cultured B cells. Lower IL-2 expression (detected only as mRNA synthesis) was also induced in the cultured B lymphocytes after incubation with cross-linking anti-IgM antibodies instead of PMA plus ionomycin. The appearance of IL-13 mRNA, but not IL-4 mRNA, was detected under the same stimulation conditions as for IL-2 mRNA. These results show that the production of IL-2 by normal B lymphocytes occurs as a late event relative to their activation and proliferation, and is in this respect subject to regulation different to that found in T lymphocytes.
Kindler
V
V
Department of Medicine, Geneva University Hospital, Switzerland.
Matthes
T
T
Jeannin
P
P
Zubler
R H
RH
D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D001402:B-Lymphocytes / Q000378:metabolism*; D019013:CD40 Antigens; D002478:Cells, Cultured; D004357:Drug Synergism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018793:Interleukin-13 / Q000096:biosynthesis / Q000235:genetics; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000888:Antibodies, Anti-Idiotypic; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D018793:Interleukin-13; D007376:Interleukin-2; D012333:RNA, Messenger; C044203:anti-IgM; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate