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At least 397 records · Page 22Linked to original sources
PubMed1977

Dimeric immunoglobulin E serves as a unit signal for mast cell degranulation.

Rat immunoglobulin E (IgE) was treated with a crosslinking reagent, dimethyl suberimidate, and fractionated by gel filtration into monomers, dimers, trimers, and higher polymers. The fractions retained substantial ability to bind specifically to mast cells. About one-third of the cell-bound dimers appeared to bind bivalently. The fractions were assayed in vivo by passive cutaneous anaphylaxis in rats, and for histamine or serotonin release in vitro using normal or tumor mouse mast cells. The monomers showed no activity, while the dimers and higher polymers gave excellent and approximately equivalent responses. We conclude that IgE that has been crosslinked to form dimers prior to the addition to mast cells can serve as a unit signal for triggering IgE-mediated exocytosis.

Animals↗
PubMed1983

Pharmacological modulation of IgE-dependent mast cell degranulation in experimental autoimmune uveoretinitis.

Immediate hypersensitivity phenomena have been shown previously to occur at the beginning of experimental autoimmune uveoretinitis (EAU) induced in Lewis rats by immunization with purified S-antigen from bovine retina. The onset time and severity of the disease were modified by modulating the mast cell (MC) function. Drugs blocking the release of mediators from MC, disodium cromoglycate and ketotifen, given as eyedrops, slightly delayed the onset and decreased the severity of inflammation. Compound 48/80, a drug effective in depleting MC of their inflammatory mediators, delayed significantly the onset, decreased and sometimes suppressed EAU, when given by the subconjunctival or intraperitoneal routes. No modification of the IgG and the IgE circulating anti-S-antibody level was demonstrated in both types of treatment, whereas in vitro reagin-dependent degranulation of peritoneal MC in the presence of the antigen was decreased in both cases. Identification of MC-bound reagins as IgE was strongly suggested by the blocking effect of anti-IgE antibodies on MC degranulation. These data confirm the link between MC activation and the onset and severity of EAU.

Animals↗
PubMed1983

Facilitation of phospholipase A2 activity by mastoparans, a new class of mast cell degranulating peptides from wasp venom.

The effect of mastoparan, Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-LeuNH2, and related peptides on the release of arachidonic acid from egg yolk lecithin liposomes, rat peritoneal mast cells, and cultured human fibroblasts was studied. In unsonicated liposomes, labeled with 1-stearoyl-2[1-14C]arachidonyl-sn-glycero-3-phosphocholine, 5 X 10(-5) M mastoparan caused a 12-, 15-, and 50-fold increase in the production of arachidonic acid catalyzed by phospholipase A2 from bee venom, eastern diamondback rattlesnake and porcine pancreas, respectively. The stimulant effect of mastoparan and related peptides was dose-dependent and further enhanced by sonication of liposomes. In contrast, melittin, while stimulating the production of arachidonic acid by phospholipase from bee venom, was inactive with the rattlesnake and pancreatic enzymes. Melittin was also only weakly active with liposomes containing stearic acid in place of arachidonic acid. Like melittin, mastoparans stimulated phospholipase activity in tissue homogenates and caused a dose-dependent release of arachidonic acid from rat peritoneal mast cells and cultured human fibroblasts prelabeled with [14C]arachidonic acid. The heptapeptide fragments mastoparan 1-7 and mastoparan 8-14, and succinylated mastoparan were ineffective. The results suggest that mastoparan and related peptides in insect venoms act, at least in part, by stimulating phospholipase activity.

Amino Acid Sequence↗