Delayed reaction to DNP conjugate prepared in vitro from the extract of homologous epidermis could be clearly detected on intradermal injection in guinea pigs sensitized by epicutaneous application of DNCB and intradermal injection of Freund’s complete adjuvant to the previously applied area, but not to DNP guinea pig serum. The animals developed the most intense delayed reaction to DNP conjugate prepared from the subcellular small granule fraction of homologous epidermis. There was significant difference in the reactivity of this conjugate and DNP-soluble fraction of the epidermis. The animals also showed positive reactions to DNP conjugates prepared from the extracts of homologous heart, liver, kidney and heterologous (human) epidermis. This finding is explainable by cross-reactivity which exists between these conjugates and DNCB conjugated in vivo to autologous epidermis.
The distribution of immune deposits in the skin of reversed passive Arthus reaction was investigated using horseradish peroxidase (HRP) as antigen. Free and non‐reacted HRP, after leaking from small vessels, spreads widely in connective tissue, in epidermis, and in hair follicles in a diffuse and homogeneous pattern. When a specific antibody is administered, HRP appears as granular deposits, which can be considered to be immune deposits, and they adhere to the tissues. When sufficient amounts of antibody is intracutaneously administered, these granular deposits are seen at the wall of venules or in the vicinity of the venules, but when a small amount of antibody is injected, the deposits are seen widely in the connective tissue and are apt to be accumulated at the basement membrane of the dermo‐epidermal junction and of hair follicles. Free HRP passes the basement membrane easily, but the immune complexes are considered unable to pass it and are deposited under it.
The number of DNP group-bearing lymphocytes in the regional lymph node, thoracic duct and peripheral blood was determined at various time intervals after painting normal guinea pigs with DNCB by the immunofluorescent method using anti-DNP antibody. The incidence of such cells in the regional node was maximal at 12 hours whereas in the thoracic duct and peripheral blood the maximum incidence was found at 0.1-2 hours after painting. Unreacted DNCB was demonstrated in both the thoracic lymph duct and the blood at least for 12 or 24 hours respectively following exposure to DNCB. The authors therefore suggest that DNCB reacts directly in vivo with the lymphocyte cell membrane of guinea pig following epicutaneous application of the chemical.
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