Lectins and anti-T monoclonal antibodies-induced changes of second messengers generating enzymes in human peripheral blood mononuclear cells.
A five min. incubation of peripheral blood mononuclear cells (PBMN) with either phytohaemagglutinin (PHA) or concanavalin A (ConA) resulted in distinct subcellular redistribution patterns of phosphatidylinositol 4,5-bisphosphate phospholipase C [PtdIns(4,5)P2-PLC] and myo-inositol 1,4,5-trisphosphate monophosphatase [Ins(1,4,5)P3-monophosphatase] activities. When compared to control cells, PHA-treated PBMN cells displayed a significant increase of PtdIns(4,5)P2-PLC and Ins(1,4,5)P3-monophosphatase relative specific activities in the nuclear fraction along with an increment (D) in enzyme amount of 6.5% and 7.3%, respectively. Incubation with B66.6, an anti-CD4 monoclonal antibody (Mab) which specifically activates CD4(+)-T cells in the absence of any other stimuli, also induced changes of these activities in the nuclear fraction, thus mimicking the effect of PHA observed in helper T cell subpopulation. No changes were detected after incubation of PBMN cells with the non mitogenic anti-CD4 MAb 101-69, or with an anti-CD3 MAb which activates T cells only in the presence of a second stimulus. On the other hand, after incubation with ConA, PtdIns(4,5)P2-PLC relative specific activity was enhanced in the microsomal fraction while the Ins(1,4,5)P3-monophosphatase activity increased in both nuclear and microsomal fractions and decreased in cytosol. An increment D of 4.6% and 10.9% for PtdIns(4,5)P2-PLC and Ins(1,4,5)P3-monophosphatase, respectively, was measured in the microsomal fraction. Only after three days of incubation with a mitogenic anti-CD2 MAb Lau-2.1.2, the PtdIns(4,5)P2-PLC activity increased in the particulate fraction of PBMN similar to ConA treatment.
Graber
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Laboratorio di Patologia Cellulare, Istituto Cantonale di Patologia, Locarno, Switzerland.
Leoni
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Carrel
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Losa
G A
GA
D000961:Antilymphocyte Serum / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D000072181:Inositol Polyphosphate 5-Phosphatases; D007963:Leukocytes, Mononuclear / Q000201:enzymology* / Q000276:immunology*; D010744:Phosphoric Monoester Hydrolases / Q000097:blood; D010835:Phytohemagglutinins / Q000494:pharmacology; D015290:Second Messenger Systems / Q000276:immunology* / Q000502:physiology*; D013347:Subcellular Fractions / Q000201:enzymology; D013601:T-Lymphocytes / Q000276:immunology; D010738:Type C Phospholipases / Q000097:blood
D000961:Antilymphocyte Serum; D010835:Phytohemagglutinins; D003208:Concanavalin A; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D010738:Type C Phospholipases