Effect of IL-4 on peripheral blood lymphocyte proliferation: implication in immunopathogenesis of H. pylori infection.
Interleukin (IL) 4 is a type 2 cytokine which has a negative immunoregulatory role in human infection. IL-4 suppresses the production of interferon-gamma and enhances IL-10 synthesis. However, the effect of IL-4 on proliferative response of lymphocytes remains to be elucidated. We have previously reported an increase in production of IL-4 in subjects with Helicobacter pylori (H. pylori) infection. To evaluate whether the increased IL-4 is responsible for the down-regulation of immune responses in H. pylori infection, we observed the proliferative response of peripheral blood lymphocytes (PBL) co-cultured with phythaemagglutinin (PHA) or H. pylori in the presence and absence of added IL-4. As we have previously shown, PHA and H. pylori may increase PBL proliferation (P < 0.001). An increase in PBL proliferation was observed when PBL were co-cultured with PHA (P < 0.001) or H. pylori (P < 0.001) in the presence of IL-4 compared to that in the absence of IL-4. The optimal dose of IL-4 to give maximal lymphocyte proliferation is 50 pg/ml for the PHA-stimulated group or 100 pg/ml for the H. pylori-stimulated group. The data suggest that the increased IL-4 does not directly contribute to suppressed lymphocyte proliferation in H. pylori infection. Further studies will be required to determine the role of IL-4 in other aspects of down-regulation of immune responses in H. pylori infection.
Fan
X G
XG
Department of Clinical Medicine, St. James's Hospital, Trinity College, Dublin, Ireland.
Yakoob
J
J
Fan
X J
XJ
Keeling
P W
PW
D002478:Cells, Cultured; D004306:Dose-Response Relationship, Immunologic; D016481:Helicobacter Infections / Q000276:immunology* / Q000382:microbiology; D016480:Helicobacter pylori; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*
D007376:Interleukin-2; D015847:Interleukin-4