Experimental design for bioassay of a material inducing strong tachyphylactic effect (anaphylatoxin)

Studies on the mechanism of hypersensitivity phenomena. III. The participation of complement in the formation of anaphylatoxin

The interaction of fresh rat and guinea pig serum with washed preformed immune aggregates has been studied with respect to the loss in hemolytic potency of the serum, diminution of the C'₃; activity, and appearance of anaphylatoxin. It has been found that the formation of anaphylatoxin, as judged by its effect on capillary permeability and smooth muscle contraction, is coincident with or subsequent to the fixation of all the known C' components. Less anaphylatoxin is formed by aggregates formed with excess antigen than those in equivalence ratio combination. C' fixation, as well as anaphylatoxin production, may be inhibited by chelation of the divalent cations, presumably by interfering with the fixation of C'₁, C'₄, and C'₂. Phlorizin suppresses the utilization of C'₃ in immune hemolysis, C' fixation by antigen-antibody aggregates, and the production of anaphylatoxin. The biological activities associated with the fixation of C' are not manifest unless C'₃ participates in this process at 37°C. It is concluded that the formation of anaphylatoxin may be regarded as a product of C' fixation.

QUANTITATIVE EVALUATION OF GUINEA-PIG ANAPHYLAXIS IN VIVO

Two methods for recording bronchoconstrictor responses to antigen injected into sensitized guinea-pigs have been used to show that the dose/response relationship is a normal pharmacological one characterized by a sigmoid curve. Studies of desensitization indicate that the progressive decrease in sensitivity to repeated administrations of the same dose of antigen follows an exponential pattern. It is suggested that this approach might form a basis for reliable quantitative investigations of anaphylactic phenomena.

Complement activation by aluminium and zirconium compounds

The activation of complement by a number of metal compounds, previously found to induce chronic inflammation, was investigated. Results obtained were compared with complement activation by inulin and zymosan. It was shown that complement activation by these metal compounds did not necessarily involve either the classical or the alternative pathways. Some of these compounds were unable to activate complement in the absence of detectable plasminogen. The results obtained indicate a relationship between the ability of these compounds to induce chronic inflammation in the guinea-pig and to activate complement.

Studies on the mechanism of hypersensitivity phenomena. IV. An isometric smooth muscle assay system

An isometric system for the assay of smooth muscle contraction is described. Studies of the nature of the response of this tissue to histamine, anaphylatoxin and specific antigen indicate important differences with respect to length of latent period and the effect of repetitive stimuli. Data are presented on the effect of variation in the calcium concentration on the responsiveness to histamine and antigen.

Regional variability in the responsiveness of guinea-pig small intestine to various stimuli has been studied. Data are presented which indicate that the rate of increase of the response to antigen, and the maximal force of the response to antigen, are temperature dependent. The responses to antigen are not significantly different after prior exposure to acetylcholine, serotonin, histamine, or potassium ions.

Contractions induced by potassium chloride are followed by markedly diminished responses to rat serum anaphylatoxin.

Further data are provided on the parallelism between C′₃ utilization and formation of anaphylatoxin from rat serum.

A quantitative method for the assay of inhibitors of acid gastric secretion in the rat

Assays of inhibitors of gastric secretion are described by a method of recording continuously acid gastric secretion in the rat. A number of doses of inhibitor comprising several assay blocks can be administered in one preparation and complete assays with known fiducial limits performed with only two rats. Assays were carried out with vasopressin against secretion induced by histamine, and with atropine, methanthelinium and atropine methylnitrate against secretion induced by methacholine.