Abstract Human polymorphonuclear neutrophils, monocytes, and lymphocytes were studied for their ability to synthesize Paf-acether when stimulated with the ionophore A 23187 (Io) or with specific secretagogues. When stimulated with Io, neutrophils produced 100 +/- 8.5 pmol Paf-acether 1 X 10(6) cells (mean +/- 1 SD, n = 5); monocytes were less efficient (44 +/- 3.3 pmol Paf-acether/1 X 10(6) cells), whereas lymphocytes were practically unable to form this mediator (1.0 +/- 0.4 pmol Paf-acether/1 X 10(6) cells). Neutrophils and monocytes released in the extracellular medium 49 and 37% of Paf-acether that they formed, respectively. We attempted to correlate the amount of Paf-acether produced by the various cell types with that of its precursors, 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine and 1-O-alkyl-sn-glycero-3-phosphocholine (2-lyso Paf-acether). In the three cell types, the amount of 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine was sufficient to ensure the formation of 2-lyso Paf-acether and consequently that of Paf-acether. The quantity of 2-lyso Paf-acether formed appeared to be the limiting factor only in the case of the neutrophils. These cells increased their synthesis of Paf-acether in the presence of exogenous 2-lyso Paf-acether. To investigate the failure of lymphocytes to produce the mediator, the acetylating step of Paf-acether formation was studied, and we found a very weak activity (0.5 +/- 0.1 nmol Paf-acether/10 min/mg protein) in this cell type as opposed to monocytes (4.0 +/- 2.3 nmol Paf-acether/10 min/mg protein) and neutrophils (17.8 +/- 5.3 nmol Paf-acether/10 min/mg protein). These activities were doubled in Io-stimulated cells. Thus, the modulation of acetyl-transferase activity appears to be a key step in the regulation of Paf-acether biosynthesis. Also, the availability of 2-lyso Paf-acether could regulate Paf-acether synthesis in human neutrophils.
Cyclomunine, a cyclic peptide extracted from Fusarium equisiti, inhibits responses of human lymphocytes to mitogens, soluble antigens and allogeneic cells and the proliferation of lymphoblastoid cell lines. Cyclomunine has little effect on small lymphocytes but acts rather on lymphoblasts. It has no effect on fibroblasts and myeloid cells. Cyclomunine partially inhibits the generation of suppressor cells induced by Con A and the generation of cytotoxic T cells in a mixed lymphocyte culture and totally inhibits the in vitro synthesis of Ig by PBL. Cyclomunine merits consideration as a new in vitro anti-lymphoblastic agent.
Abstract. Hepatitis B virus (HBV) DNA sequences have been detected in leucocytes from HBV‐infected individuals. The aim of this study was to assess the specificity of HBV for a special leucocyte subset in nine healthy chronic HBV carriers, nine HBs antigen‐positive patients with chronic active hepatitis, 16 HBs antigen‐negative haemophiliacs with HBc and/or HBs antibodies, and 10 patients with HBV‐related systemic necrotizing vasculitis. HBV‐DNA sequences were found by Southern blot hybridization in the leucocytes of 15 out of the 44 (34%) patients. The prevalence was not significantly different between the four groups. HBV‐DNA was found in the CD4+ cells (9/11) as well as in the CD8+ cells (4/11), B cells (4/12) and monocytes (2/12). In conclusion, leucocytes, and particularly CD4+ lymphocytes, are frequently infected by HBV in patients with HBV serum markers.
