Synthesis of IL-13 by human B lymphocytes: regulation and role in IgE production.
BACKGROUND
Our laboratory has demonstrated previously that human tonsillar B lymphocytes express IL-13 mRNA OBJECTIVE: We sought to investigate IL-13 production by human B cells and the association between B cell-derived IL-13 and IgE secretion.


METHODS
Human B lymphocytes were isolated from tonsils and purified by means of rosetting with sheep RBCs or positive or negative selection with magnetic beads. They were stimulated with anti-CD40 antibodies with or without recombinant IL-4. Total mRNA was extracted, and IL-13 mRNA was measured by means of standard RT-PCR or by means of real-time PCR with commercially available primers. B cells were cultured with or without IL-13 neutralizing antibodies, and C epsilon transcripts and supernatant IgE levels were measured.


RESULTS
IL-13 mRNA was detected in human B lymphocytes stimulated with anti-CD40 antibodies and IL-4 or IL-2 but not in unstimulated B cells. Real-time PCR demonstrated a 10- to 15-fold increase in IL-13 mRNA, maximizing at 36 hours. IL-13 protein was detected from B lymphocytes on day 3 and accumulated through day 7. The synthesis of IL-13 required both CD40 and IL-4 stimulation. The presence of IL-13 was confirmed by means of intracellular staining of cultured B lymphocytes and antigen-stimulated nasal biopsy specimens from atopic individuals. Addition of IL-13 neutralizing antibodies to purified B-cell cultures inhibited IgE production by up to 80% and diminished IgE (C epsilon) transcripts by 50%.


CONCLUSIONS
Human B lymphocytes express IL-13 mRNA after ligation of CD40 and the addition of cytokines. Human B lymphocytes produce significant IL-13, and neutralization of IL-13 impairs IgE synthesis. IL-13 might be an important autocrine growth factor for IgE-producing B lymphocytes.
Hajoui
Oumnia
O
Division of Allergy and Immunology, McGill University Health Center-Montreal Children's Hospital, Montreal, Quebec H2X 2P2, Canada.
Janani
Ramesh
R
Tulic
Meri
M
Joubert
Philippe
P
Ronis
Tova
T
Hamid
Qutayba
Q
Zheng
Huaien
H
Mazer
Bruce D
BD
D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D001706:Biopsy; D019013:CD40 Antigens / Q000276:immunology; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D005786:Gene Expression Regulation; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007073:Immunoglobulin E / Q000378:metabolism*; D018793:Interleukin-13 / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000276:immunology; D008213:Lymphocyte Activation; D009666:Nose / Q000276:immunology; D014066:Palatine Tonsil / Q000166:cytology / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D019013:CD40 Antigens; D018793:Interleukin-13; D012333:RNA, Messenger; D015847:Interleukin-4; D007073:Immunoglobulin E