title: Immunoregulatory effects of phospholipase A2 (PLA2) on the proliferation of human lymphocytes.
abstract: Extracellular phospholipase A2 (PLA2) is a proinflammatory enzyme found especially in the inflammatory exudate to modulate blood flow to areas of antigen stimulation. In this study we found that PLA2 exerted a biphasic effect on the proliferation of phytohemagglutinin (PHA)-stimulated human mononuclear cells (PHA MNC). At low concentrations range from 0.001 to 1 U/ml, PLA2 enhanced the proliferation of PHA MNC (maximal increase was 37.0 +/- 5.67%). Conversely, at concentrations over 10 U/ml, PLA2 markedly suppressed the PHA-induced MNC proliferation (maximal decrease was 88.86 +/- 2.89%). PLA2 was non-toxic to lymphocytes after three days culture, unless the concentration was higher than 100 U/ml. The membrane polarization of PHA-stimulated lymphocytes was also increased by PLA2 at a low concentration. In addition, PLA2 displayed a similar effect on the proliferation of streptokinase-streptodornase (SK/SD) or allogeneic cell stimulated lymphocytes. The change of lymphocyte proliferation by PLA2, was parallel to the change of percentage of helper T cells. Furthermore--a CD4-rich population was proved more susceptible to PLA2 effect than a CD8-rich population. Para-bromophenacyl bromide (pBPB), an irreversible inhibitor of PLA2, abrogated the biphasic effect of PLA2 on PHA MNC proliferation. These results suggest that PLA2 plays a regulatory role on immune reactions by modulating the percentage of helper T cells.
authors.affiliation: Department of Medicine, Veterans General Hospital-Taipei, Taiwan, ROC.
authors.forename: C L
authors.initials: CL
authors.lastname: Yu
authors.forename: C Y
authors.initials: CY
authors.lastname: Tsai
authors.forename: S Y
authors.initials: SY
authors.lastname: Hong
authors.forename: C S
authors.initials: CS
authors.lastname: Lue
authors.forename: C C
authors.initials: CC
authors.lastname: Chiu
authors.forename: B N
authors.initials: BN
authors.lastname: Chiang
authors.forename: S H
authors.initials: SH
authors.lastname: Han
authors.forename: S R
authors.initials: SR
authors.lastname: Wang
mesh_terms: D003851:Deoxyribonucleases / Q000494:pharmacology; D006801:Humans; D007107:Immune System / Q000187:drug effects*; D008213:Lymphocyte Activation / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D010835:Phytohemagglutinins / Q000494:pharmacology; D013300:Streptokinase / Q000494:pharmacology; D016176:T-Lymphocyte Subsets / Q000187:drug effects
chemical_list: D010835:Phytohemagglutinins; D003851:Deoxyribonucleases; D010741:Phospholipases A; D054467:Phospholipases A2; D013300:Streptokinase