Characterization of a factor from rat serum with blocking activity in the passive cutaneous anaphylactic reaction

Inhibition of in vitro and in vivo mast cell degranulation by Taenia crassiceps metacestodes in vitro incubation products

In vitro released products of T. crassiceps metacestodes (TcIP) harvested from the peritoneal cavity of NMRI mice were tested for inhibitory effects on the in vitro degranulation of peritoneal mast cells (MCs) of normal mice (NMRI) and rats (Wistar) and on the in vivo degranulation of rat (Wistar) skin MCs (PCA-assay). In vitro degranulation was elicited chemically (compound 48/80, polymyxin B or the bee venom peptide, mellitin). In vivo degranulation was triggered immunologically (anaphylactic systems ovalbumin/anti-ovalbumin or Fasciola hepatica crude fluke extract antigen/serum of fluke-infected rats (Wistar]. In vitro degranulation of murine peritoneal MCs or the in vitro histamine release of rat peritoneal MCs normally induced chemically was significantly inhibited when the MCs were preincubated with the TcIP or with serum of T. crassiceps-infected NMRI mice from day 35 post infection and thereafter. In vitro degranulation of peritoneal MCs of infected mice was strongly inhibited beginning on day 10 after infection. Also in vivo degranulation of the IgE-sensitized rat skin MCs was significantly reduced by intradermal injection of the TcIP before (6, 3 and 1 h) antigen challenge and by preinjection (1 h) of serum from infected mice (day 80 p.i.)-The inhibitory effect was also demonstrated after immunoadsorption of mouse serum proteins naturally contaminating the TcIP. Heating (100 degrees C/15 min), even in the presence of 0.25 M HCl, did not suppress the inhibitory activity.

Activation of human complement by rat peritoneal mast cells and its inhibition by a rat serum factor

The effects of normal sera from humans, rats, and guinea pigs on unsensitized rat peritoneal mast cells were studied in vitro. Five to 20% fresh human sera induced mast cell death and substantial histamine release. The factor was heat labile. Neither hereditary C3-deficient sera nor experimentally C1q-depleted sera showed cytotoxicity. The CH50 activity of human serum was decreased to about one half after a 15-min incubation with 2 X 10(6) mast cells/ml at 37 degrees C. The cytotoxic activity and CH50 reduction were completely eliminated by an addition of 10 mM Mg-EGTA to the serum. These data demonstrated that unsensitized rat mast cells served as both the initiator and target of complement activity when human serum was used as a complement source. Requirements of both Ca++ and C1q suggested the activation of the classical pathway of complement. Fresh 5-20% sera from rats and guinea pigs, on the other hand, showed neither cytotoxicity nor CH50 reduction. Furthermore, these sera strongly inhibited the human serum-induced reaction. The latter results indicated the presence of a modulating factor in rat and guinea pig sera, which inhibits mast cell associated complement activation.

Inhibition of histamine release in vitro by a blocking factor from human serum: comparison with the iron binding proteins transferrin and lactoferrin

Recently, we described the presence of a blocking factor (BF) in rat serum, which inhibited the histamine release from rat mast cells in vivo and in vitro. The blocking activity was demonstrated in human serum as well. Qualitative analysis of the purified preparations demonstrated a major component with an apparent molecular weight of 70,000 daltons. In human serum the blocking factor was identified as transferrin (TF) by serological and biochemical methods. BF (DEAE-peak 1) and the iron binding proteins transferrin and lactoferrin (LF) are shown to inhibit the histamine release in vitro. The dose response curves reveal that inhibition by these proteins is dependent on their degree of iron saturation. Furthermore, unlike lactoferrin, the effects of transferrin and BF (DEAE-peak 1) follow the same pattern. Their mechanism of action remains to be elucidated.

Inhibition of histamine release from rat peritoneal mast cells by a factor from human serum--identification as transferrin

Recently, we described the presence of a blocking factor (BF) in rat serum which inhibited the histamine release from rat mast cells in vivo and in vitro. The blocking activity was demonstrated in human serum as well. Purification of the human-BF was carried out in a similar way as previously described for the rodent molecule. Both protein fractions produced a marked suppression of histamine release from rat mast cells and human basophils in a dose-dependent fashion. Qualitative analysis of the purified preparations demonstrated a major component with a molecular weight of 70,000 daltons. In human serum the blocking factor was identified as transferrin by serological and biochemical methods. It is suggested that this molecule may play an important role in regulating histamine release during allergic and inflammatory reactions.

Interaction of monoclonal antibodies with the IgE-receptor on rat mast cells and rat basophilic leukemia (RBL) cells

The close relation between rat mast cells and rat basophilic leukemia (RBL) cells with regard to the presence of receptors for IgE and Fc gamma led us to generate monoclonal antibodies directed against cell surface antigens. Hybridomas were obtained by the fusion of NS1 mouse myeloma cells with murine spleen and lymph node cells. The culture supernatants were assayed by two ELISA techniques: a) for the production of mouse immunoglobulin in general and b) for antibodies directed against surface antigens of RBL cells. For this purpose RBL cells were attached to polyvinyl chloride microtitre plates. Eight hybrids produced antibodies directed against surface antigens on RBL cells. Hybrids were cloned and characterized with regard to their isotype and light chains. All eight clones secreted IgM with K light chains. Immunofluorescence studies performed with RBL cells revealed that all eight antibodies were able to show a specific fluorescence. Furthermore, four of these eight antibodies also showed a specific fluorescence with purified rat mast cells. These four antibodies were analyzed as to their ability of interacting with the IgE-receptor on RBL cells and purified rat mast cells. They reduced the binding rate of radiolabelled rat IgE to RBL and rat mast cells. A mutual inhibition of the passive cutaneous anaphylaxis (PCA) reaction in the rat by either mixing mouse reaginic serum directed against 2,4-dinitrophenol bovine serum albumin (DNP-BSA) or by mixing monoclonal mouse anti-DNP IgE with the monoclonal mouse anti-cell surface (rat basophilic leukemia, rat mast cell) IgM was determined.(ABSTRACT TRUNCATED AT 250 WORDS)