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Delayed skin hypersensitivity to specific antigen was enhanced when the antigen was given intradermally with Vibrio cholerae neuraminidase in sensitive subjects. No enhancement of skin test response was seen when inactivated enzyme was used. Neuraminidase exhibited no effect on negative skin-test response in non-sensitive recipients and no re!w1ion at the site of this enzyme was observed in any instance, suggesting that the enhancement effect is immunological in nature. [ABSTRACT FROM AUTHOR]

Chickens of four inbred lines were tested for the development of delayed hypersensitivity to mycobacterial antigens. It was found that WA and WB lines failed to develop tuberculin hypersensitivity. On the other hand, IB line was a strong responder, while the response of CB line was intermediate. [ABSTRACT FROM AUTHOR]

In order to determine the relationship between the level of circulating reaginic (IgE) antibody and degree of cutaneous hypersensitivity, rats producing different titres of reaginic antibody were assessed for skin test reactivity by means of the active cutaneous anaphylaxis test. Skin reaction diameters of ovalbumin-sensitive rats were similar whether they were producing low or markedly elevated levels of ovalbumin reagins. In rats infected with Nippostrongylus brasiliensis, skin test reactivity to N. brasiliensis antigen was demonstrable before reagin became detectable in the circulation. It increased to maximum shortly after the appearance of circulating reagin, and thereafter showed no significant increase commensurate with the further rise in reagin titre. The results show that in the rat there is no direct quantitative relationship between the size of skin test reactions and the level of specific circulating reaginic antibody. [ABSTRACT FROM AUTHOR]

Contact sensitivity was produced in mice by applying an alcoholic solution of picryl chloride or 2-phenyl-4-ethoxymethylene oxazotone (oxazolone) to the abdominal wall. It was assessed by painting the ear with the contact sensitizing agent dissolved in olive oil and measuring the increase in ear thickness 24 hours later. Contact sensitivity to picryl chloride was depressed by pre-treatment with the sulphonic acid derivative of picric acid. Complete depression was obtained when either two large doses or multiple small doses were given and in the former case this complete depression was still present 6 weeks after the last injection of the sulphonic acid. Similar pre-treatment with oxazolone depressed contact sensitivity to oxazolone in some but not all mice. Pre-treatment with the folic acid antagonist amethopterin before and during sensitization almost completely abolished contact sensitivity, while a single larger dose given 48 hours before sensitization only had a small effect. Mice whose immune response to picryl chloride had been depressed by pretreatment with sulphonic acid and methotrexate were used to study restoration of immune competence by normal lymphoid cells. No restoration was observed when unirradiated recipients were used. However, a mixture of lymph node and bone marrow cells and, to a lesser extent thymus and bone marrow cells, restored immune competence to picryl chloride in irradiated recipients. It was concluded that irradiation favoured the restoration of immune competence by normal lymphoid cells and that a mixture of lymph node and possibly thymus cells with bone marrow cells was able to cause restoration. [ABSTRACT FROM AUTHOR]

A preliminary experiment showed that the injection of bovine γ-globulin into guinea-pigs with delayed hypersensitivity to bovine γ-globulin reduced the 24-hour skin reactions to bovine γ-globulin and (to a lesser extent) PPD. The peritoneal exudate cells from the desensitized donors had a reduced ability to transfer delayed hypersensitivity to bovine γ-globulin but a normal ability to transfer delayed hypersensitivity to PPD. Likewise, it was possible to diminish the passive transfer of delayed hypersensitivity to bovine γ-globulin by peritoneal exudate cells, by exposure of the ceils to bovine γ-globulin in vitro. The recipients were tested immediately after cell transfer. This in vitro desensitization was specific, in that the transfer of delayed hypersensitivity to PPD was unaffected. Exposure of cells in vitro to hypotonic conditions and antibody to guinea-pig γ-globulin did not prevent the passive transfer of delayed hypersensitivity. [ABSTRACT FROM AUTHOR]

The effect of total body irradiation on the development of delayed hypersensitivity and on the febrile response to specific antigen has been studied in guinea-pigs with the following results: 200 R. whole body irradiation in guinea-pigs, while suppressing circulating antibody response, did not prevent the development of delayed hypersensitivity. Irradiated and non-irradiated hypersensitive animals had an equal febrile response to systemic challenge with specific antigen. Serum from antigen-challenged, irradiated, hypersensitive animals contained a pyrogenic factor of the endogenous serum type capable of producing fever in normal recipients. These results support the conclusion that production of circulating specific antibody is not essential either for development of delayed hypersensitivity or for the febrile response of the hypersensitive animal to specific antigen. [ABSTRACT FROM AUTHOR]

Some assumptions underlying the attribution of a high discriminatory capacity to anaphylactic tests have been investigated in model systems, using two tests of the anaphylactic response—the Dale-Schultze reaction and the measurement of histamine released from chopped lung. It has been demonstrated that there may be no response to challenge with a second antigen after desensitization to the first even though the tissues can be shown to be sensitized to the second antigen, i.e. there is a possibility of the occurrence of ‘false’ negative results. The potentiality of response to the second antigen appears to depend partly on the proportion it formed of the sensitizing mixture and partly on the absolute dose used in sensitization. It has been confirmed that desensitization is a graded phenomenon related to dose of antigen and it is shown that it is reversible with time. These factors are likely to complicate the performance and/or interpretation of experiments with tissue extracts and constitute a source of potential false positive results. These factors are of less importance with the histamine-release test than with the Dale-Schultz test. For the Dale-Schultz reaction the ileum proved to be a more satisfactory test tissue than the uterus. In general, there was no significant difference in discriminatory capacity between the histamine-release test and the Dale-Schultz test, but there were more sources of error in the performance of the Dale-Schultz test, while the histamine-release test though more laborious to do gave results which were more amenable to statistical analysis. It is concluded that with careful experimental design the tests could possibly be of use in some investigations of antigen mixtures provided that the sources of false positive results were recognized and due precautions taken. [ABSTRACT FROM AUTHOR]

The sensitivity of two anaphylactic tests, the Dale-Schultz reaction and the measurement of histamine released from chopped lung, have been investigated and compared in model systems. Both tests proved to be highly sensitive in animals sensitized to a single antigen, the Dale-Schultz test being more sensitive on occasion, but less consistent than histamine-release from the lung. In general, the sensitivity to a particular antigen was decreased if more than one antigen was used for sensitization. [ABSTRACT FROM AUTHOR]

The use of human leucocytes for in vitro studies of histamine release is reviewed. Several theoretical aspects and applications of the in vitro procedure are discussed. These include sensitivity of the cells to antigen as a reflection of disease severity, in vitro assays of reagin and the effect of parenteral immunization on the activity of human reaginic and blocking antibodies. [ABSTRACT FROM AUTHOR]