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Kinetics of primary and booster-specific and total IgE responses to distinct antigenic stimuli were studied in two inbred rat strains, Brown­Norway (BN) and Lewis. and one outbred, Sprague­Dawley (SD). The rats were immunized three or four times at intervals varying between 15 and 22 days by subcutaneous injections of 10 μg ovalbumin, keyhole limpet haemocyanin (KLH) or bovine serum albumin (BSA) mixed with 10 mg aluminium hydroxide gel. IgE anti- bodies were measured in sera by PCA titres. High responses were obtained in BN rats (PCA titres about 10,000 after booster) and low responses in Lewis and SD rats. Positive booster responses were obtained in the three strains. Peritoneal mast cells collected from the three strains after immunization could degranulate on in vitro addition of specific antigen. In contrast, BN mast cells were bad receptors while Lewis and SD mast cells were good receptors for in vitro passive sensitization by mouse IgE antibodies. Total serum IgE was assayed by an in vitro competitive inhibition bioassay (CIB). The values before immunization were higher in BN (1–4 μg/ml) than in Lewis (<0.25 μg/ml) or SD rats (0.6 μg/ml). After immunization, a striking in- crease could be observed in BN rats (up to 170 μg/ml). There was no parallel between total IgE and IgE anti- body levels at different times after immunization. [ABSTRACT FROM AUTHOR]

Possibility of inhibition of an efficient in vitro IgE-sensitization system was studied. The sensitization of mouse peritoneal mast cells with an anti-ovalbumin IgE-rich fraction of serum, as tested by ovalbumin-induced degranulation, was inhibited by previous incubation with antisera of another or of no specificity. Fractionation and other experiments showed that the inhibiting activity correlated with IgE content, IgG 1 did not seem to have an effect. Sensitization was also inhibited by rat myeloma IgE, 50 ng giving a 50 per cent inhibition. Plots of the logarithms of rat and mouse IgE concentration vs their inhibitory effect on sensitization gave two parallel linear curves, indicating that mouse and rat IgE compete for the same receptor sites. It was thus possible to use this system as a sensitive bioassay for both mouse and rat IgE levels and, by comparing inhibition by mouse IgE to that by a known rat IgE standard, to obtain not only relative data but absolute mouse IgB levels. This, and also a better discrimination of IgB doses, was the major advantage of this bioassay in relation to the equally sensitive anti-IgE degranulation tests. [ABSTRACT FROM AUTHOR]

Mouse and rat IgE fix firmly to the peritoneal mast cells from the other species, sensitizing them for anaphylactic reaction. Sensitization with IgE can be demonstrated by inducing degranulation either with specific antigens or with corresponding anti-IgE. Sensitization of rat mast cells by mouse IgE antibodies is more easily obtained than that of mouse mast cells by rat IgE antibodies, In this case, anti-IgE-induced degranulation is higher than antigen-induced degranulation, Heterologous sensitization by IgE is time requiring and temperature-dependent. Its kinetics depend upon IgE concentration. Cross-reactions between IgE from one species and anti-IgE from another species have been observed: anti-IgE for one species is able to neutralize PCA reaginic activity of sera from the other species; anti-rat IgE induces degranulation of mouse actively sensitized mast cells. The results suggest strongly that there exists a structural and functional similarity between the IgE molecules from the two species. [ABSTRACT FROM AUTHOR]

Immunochemical identification of a distinct immunoglobulin class associated with mouse reaginic antibody and designated IgE has been performed. An antiserum against mouse reaginic antibody was prepared in rats by immunization with homologous peritoneal mast cells sensitized with mouse reaginic antibody. This antiserum, after adequate absorption, recognized only one component existing in mouse serum or fractions of serum containing reaginic antibody. This component was not any of the already known γ1, γ2, IgA or IgM immunoglobulins; its immunoglobulin nature was indicated by its antigen-binding capacity in radioimmunodiffusion analysis. Fractionation experiments (zone electrophoresis, gel filtration on Sephadex G-200) showed that there was a strict association between reaginic anaphylactic activity and IgE immunoglobulin. Molecular weight of IgE was found to be about 200,000. In biological tests, anti IgE neutralized anaphylactic activity attributed to reaginic antibody, but not that attributed to γ1-antibody. Anti-IgE degranulates normal and sensitized mouse peritoneal mast cells, and rat peritoneal mast cells after they have been sensitized by mouse reaginic antibody. [ABSTRACT FROM AUTHOR]

In vitro degranulation of mouse peritoneal mast cells and release of histamine were induced by the addition at 37° of anti-mouse serum or antimouse γ-globulin rabbit antibody. The release of histamine does not depend upon complement, and seems to be due to the reaction of the antibody with the homologous γ-globulin present on the surface of the mast cells. [ABSTRACT FROM AUTHOR]

The time course of production in the mouse circulation, after different schemes of immunization, of reagin-like and γ1 antibodies, as measured by the ability of the antisera to induce thermolabile long-latence and thermostable short-latence PCA reactions, has been studied. γ1 antibody was obtained in all schemes of immunization and its amount in antiserum increased with time. Reagin-like antibody appeared on the 7th day after immunization with sufficient dose of ovalbumin and adjuvant, and on later days with less efficient antigens such as DNP-BSA and DNP-BGG. Maximal amounts of the reagin-like antibody were reached in the early days after immunization and its presence in the circulation had a somewhat transient character; however, it persisted in the circulation for periods of more than 60 days, on occasion. The time course of antigen-induced histamine release from washed peritoneal mast cells of the immunized mice was also studied. A correlation was observed between the histamine release and the production of reagin-like antibody. It is suggested that the antigen-induced histamine release from washed peritoneal mast cells may be taken as an indication of the production of reagin-like antibody. Some quantitative aspects of the PCA and histamine release reactions were also studied. PCA reactions were affected similarly by varying either dilution or volume of the antiserum intradermally injected. Histamine release from peritoneal mast cells did not seem to be affected specifically by excess of antigen. [ABSTRACT FROM AUTHOR]