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The effectiveness of antigen aerosol-induced desensitization has been investigated in guinea-pigs actively sensitized with antigen, alone or incorporated in Freund's adjuvants. Rates of desensitization, and the ability of animals to regain anaphylactic hypersensitivity following intensive desensitization, have been considered in terms of relative rates of antibody production, levels of circulating antibody, and qualitative differences in the antibody produced. A protective component observed during desensitization in adjuvant-treated animals is considered to be a property both of high levels of circulating antibody and of the presence of certain non-specific factors which interfere with the sensitization process. [ABSTRACT FROM AUTHOR]

Passive cutaneous anaphylaxis in the guinea pig has been studied with rabbit antibody to a series of antigens of differing molecular weight. The results indicated that at a given antibody level the weight of antigen needed to elicit a reaction increases with its molecular weight. Previous observations have been confirmed that the amount of antigen needed to elicit a reaction at a high level of antibody is less than that required at a lower level. The results suggest that extremely small amounts of small molecular weight antigens might be sufficient to produce anaphylactic symptoms in highly sensitive individuals. [ABSTRACT FROM AUTHOR]

Reverse passive cutaneous anaphylaxis experiments were performed in guinea pigs with rabbit gamma globulin and human gamma globulin as antigens and horse, sheep or hen sera containing antibodies against these antigens. These antibodies were unable to directly sensitize the guinea-pig skin but when the reverse technique was used, namely, the antigen (gamma globulin) was injected before the antibody, characteristic anaphylactic reactions were obtained. It is concluded that, if a suitable antigen is used, which can be fixed to the host by the reverse technique, sera from species which cannot directly sensitize the guinea pig can nevertheless give typical anaphylactic reactions. [ABSTRACT FROM AUTHOR]

The capacity of denatured proteins to provoke anaphylactic sensitivity and delayed sensitivity in guinea pigs has been investigated. It has been found that heat-denatured proteins are as effective as native proteins in provoking delayed hypersensitivity to either material, in spite of the fact that such denaturation greatly modifies their antigenicity from the point of view of antibody production. Pure delayed hypersensitivity, moreover, occurs regularly in response to extremely minute amounts of a good antigen, whether native or denatured. It is further shown that immunological cross-reactivity can be demonstrated regularly by means of the delayed hypersensitivity reaction in guinea pigs, at a time when no cross-reacting antibodies of conventional type can be found. The significance of these observations in regard to the relationship between delayed hypersensitivity and antibody production is discussed. [ABSTRACT FROM AUTHOR]

Mast cell damage, characterized by loss of granules, occurs when the tissues of sensitized guinea pigs are brought into contact with antigen in vivo or in vitro. Quantitative studies on the mesenteries of passively sensitized guinea pigs show that the mast cell response to antigen is well correlated with the development of anaphylactic shock. After multiple sensitization contact with different antigens caused cumulative, but not complete, disappearance of mast cells. Antigen-antibody interactions, in which antisera were from species which do not sensitize guinea pigs passively for anaphylaxis, did not cause mast cell damage. Reversed passive anaphylaxis and mast cell damage were elicited when the antigen was a suitable γ-globulin, but not an albumin. Antiserum against homologous γ-globulin causes typical anaphylaxis and mast cell degranulation, whereas antiserum against Forssman antigen causes capillary damage without mast cell changes, and antiserum against homologous albumin is ineffective. These findings can be explained by the hypothesis that mast cell damage occurs as a result of antigen-antibody interaction, when one of the reagents is reversibly adsorbed at the mast cell surface, and when they are together capable of activating some process or agent whose further action depends upon the metabolic integrity of the cells. [ABSTRACT FROM AUTHOR]

Using the criteria of generalized anaphylaxis, the Schuhz­Dale test, and mast cell degranulation occurring on contact with antigen in vitro, a study has been made of the ability of antisera, prepared in various species, to sensitize guinea pig tissues passively. Whereas small amounts of guinea pig and rabbit antibodies and rather larger amounts of monkey, dog and human antibodies were effective, antibodies from goat, horse, rat, fowl and a human auto-immune thyroid antiserum were ineffective. These results are in general agreement with those in the literature. Using antibodies labelled with 131I, no gross differences were found between those which sensitized and those which did not, either in respect of uptake on guinea pig mesentery in vitro, or retention in the tissue after uptake in vivo. By means of antigen labelled with 131I it was also shown that the antibody adsorbed on guinea pig mesentery could combine equally well with antigen, whether the antibody came from rabbit (sensitizing) or rat (non-sensitizing). These experiments also indicated that the amount of adsorbed antibody necessary for sensitization is very small. Reversed passive anaphylaxis was studied with a variety of different antigen-antibody systems, using the criteria listed above. It occurred when, but only when, the antigen was a γ-globulin, and when both antigen and antibody globulins came from species whose antibodies were able to sensitize guinea pigs for direct passive anaphylaxis. It is concluded that the explanation of the differences between antibodies or antigens which sensitize guinea pigs passively, and those which do not, is to be found in the nature of the antigen-antibody combination as well as in the manner of ‘fixation’ on the tissues. The possible importance of ability to activate guinea pig complement is discussed. [ABSTRACT FROM AUTHOR]

The histamine forming capacity and histamine content of tuberculin skin reactions have been studied in the rat. An increase in HFC and a concomitant decrease in histamine content occur. Both changes are maximal 12 hours after injection of antigen. The results suggest that histamine may play a role, although a minor one, in the tuberculin reaction of the rat. [ABSTRACT FROM AUTHOR]