Evaluation of a novel delayed-type hypersensitivity assay toCandida albicansin adult and neonatal rats

Abstract

Delayed-type hypersensitivity (DTH) is a T-cell-mediated immune response that may be used for immunotoxicity testing in non-clinical species. However, in some cases DTH assays using T-dependent antigens may be confounded by the production of antibodies to the antigen. The authors have previously modified a DTH assay, initially validated in the mouse, for use in juvenile rats to assess the effect of immunosuppressive drugs on the developing rat immune system. The assay measures footpad swelling induced by subcutaneous footpad injection of Candida albicans (C. albicans) derived-chitosan in rats previously sensitized with C. albicans. Antibodies to chitosan are not produced in this model. However, considerable inter-animal variability inherent in the footpad swelling assay can make it difficult to precisely quantify the magnitude of the immune response and inhibition by immunosuppressants, particularly if complete suppression is not observed. This report describes the development of an ex vivo assay to assess DTH in rats using interferon (IFN)-g production by splenocytes, obtained from rats sensitized with C. albicans, as the quantifiable measure of the DTH response. Adult and neonatal rats administered dexamethasone (DEX), a known immunosuppressant, exhibited immunosuppression as evidenced by a reduction in ex vivo IFNg production from splenocytes challenged with C. albicans-derived chitosan. Current data indicate that the ex vivo based DTH assay is more sensitive than the conventional footpad swelling assay due to a lower background response and the ability to detect a response as early as post-natal day (PND) 12. The ex vivo based rat DTH assay offers a highly sensitive and quantitative alternative to the footpad swelling assay for the assessment of the immunotoxic potential of drugs. The increased sensitivity of the ex vivo DTH assay may be useful for identifying smaller changes in response to immunotoxic drugs, as well as detecting responses earlier in animal development.

Effect of Staphylococcus aureus Thermostable DNase on Some Immunological Parameters

“…Sensitized T-cells formed as a result of the initial exposure, and, upon secondary challenge with the same antigen, a vigorous response by the sensitized Tcells accompanied with the release of several cytokines and tissue swelling. Because DTH relies on antigen processing by APC and subsequent presentation to T-cells at least 24-72 h are needed for the response to occur, which may take only minutes to manifest [22] . DNase has been shown to increase the production of IL-4 that enhances Th2 immunity by inhibiting Th1 responses through the repression of IL-12 signaling [19].…”

Examination of the Microbial Spectrum in the Etiology of Erythema Nodosum: A Retrospective Descriptive Study

“…When tolerance mechanisms become defective, the commensal form changes into the pathogenic form and expresses its virulence traits [29]. In our literature search, we found no specific documentation on the association of C. albicans with EN, although the delayed-type hypersensitivity reaction to C. albicans is already well known and has been historically used to evaluate the immune competence experimentally in humans [30]. In fact, the essential subject that might be considered in this aspect is whether these microorganisms are among the overlooked etiological factors in EN cases in which there exists a female predominance, especially in patients who fall into the “idiopathic” category.…”

Immunomodulatory and AntiOxidant Potential of Polyherbal Dhatryadi Rasayana in the Form of Churna and Granules

“…On the 14th day, animals were injected subcutaneously with 0.1 mL of 10% SRBCs in NS into the left hind footpad of the rats. A vernier calliper was used to measure the footpad thickness after 4, 8, and 24 h in order to assess the degree of delayed-type hypersensitivity (DTH) reaction in the rats . The change in the thickness of the left hind paw and right hind paw was used as an extent of DTH reaction by the following expression (8) and was expressed as a mean percent increment in thickness/edema: Left foot pad challenged with antigen − Right foot pad control Left foot pad challenged with antigen × 100 …”

“…A vernier calliper was used to measure the footpad thickness after 4, 8, and 24 h in order to assess the degree of delayed-type hypersensitivity (DTH) reaction in the rats. 27 The change in the thickness of the left hind paw and right hind paw was used as an extent of DTH reaction by the following expression (8) and was expressed as a mean percent increment in thickness/edema: …”