Feedback suppression of the immune response in vivo. I. Immune B cells induce antigen-specific suppressor T cells

Stimulated lymphocytes are capable of synthesizing and secreting a variety of lymphokines which can affect the functions of several types of target cells. We report here the existence of a soluble factor released by activated human mononuclear leukocytes which produces a selective inhibition of human pulmonary fibroblast migration. This fibroblast migration inhibitory factor (FIF) was produced by antigen- or mitogen-stimulated human peripheral blood mononuclear leukocytes (PBML) and purified T cells. It inhibited the migration of ⁵¹Cr-labeled fibroblasts in a dose-dependent fashion with optimal effect (65–70% inhibition) obtained at 1:10 dilution and 8–20 hr of incubation. Sephadex G-100 fractionation revealed most activity to be found between 28,000 and 34,000 daltons. FIF was stable at 56 °C for 15 min, but destroyed at 80 °C or at low pH. This factor may play an important role in the modulation of fibrogenesis and healing processes by the immune system.     

Purification and characterization of two distinct dipeptidyl aminopeptidases in soluble fraction from monkey brain and their action on enkephalins

Two distinct dipeptidyl aminopeptidases, which were designated DPP-A and DPP-B, were purified from soluble fraction of monkey brain using Leu-enkephalin as the substrate. The enzymes were purified 187 and 136 fold, respectively. Both enzymes showed the optimum pH in neutral range. Their molecular weights were almost equal and were estimated to be about 100,000. Their Km values with Leu-enkephalin as the substrate were 5.6 X 10(-5) and 1.1 X 10(-5) M, respectively. Among synthesized substrates, the highest affinity of the enzymes was toward arginyl-arginine beta-naphthylamide with the Km values of 6.25 X 10(-5) and 6.41 X 10(-5) M, respectively. Both enzyme activities were inhibited by the metal-chelators DFP and PCMB. Two hundred fifty microM arphamenine A inhibited DPP-A and -B with inhibition of 36.6% and 44.1%, respectively. Beta-endorphin, ACTH, and glucagon inhibited only DPP-B, while beta-lipotropin and angiotensin II inhibited both DPP-A and -B when Leu-enkephalin was used as the substrate.     

The Effects of Cobra Venom Factor,an Inhibitor of the Complement System,on the Sequence of Morphological Events in the Rat Kidney in Experimental Pyelonephritis

Acute experimental pyelonephritis has been produced by a combination of mechanical ureteral obstruction and intravenous injection of E. coli (strain IMRU-54). The effects of administration of cobra venom factor, an inhibitor of the complement system, on the sequence of morphologic events in the kidneys have been studied by light and electron microscopy.Pronounced bacterial colonization and suppression of the infiltration of acute inflammatory cells into the kidney were present in the cobra venom factor treated rats on day 2. In these rats, in which the infiltration of polymorphonuclear leukocytes was inhibited, renal structural damage was significantly reduced. The findings appear to indicate that the polymorphonuclear leukocytes infiltrating into the kidney play some role in damaging the renal parenchymal tissue in the early phase of E. coli induced acute pyelonephritis in rats.