Histopathology of Delayed-Onset Hypersensitivities in Contact-Sensitive Guinea Pigs

Abstract

We have studied the specificity of macroscopic responses and the corresponding cellular infiltrates in Giemsa-stained, glycol methacrylate embedded tissue sections of delayed skin reactions elicited by contact sensitizers, homologous and heterologous hapten-protein conjugates, and tuberculin (PPD) in guinea pigs. The animals were sensitized with contact sensitizers emulsified in Freund’s complete adjuvant and tested at 19 days and, after repeated contact testing with homologous sensitizer, at 48 days after sensitization. At both times, all delayed reactions contained numerous mononuclear cells. The reactions elicited by contact sensitizer or hapten-protein conjugate also contained significant numbers of basophils which were lacking in PPD reactions. Contact reactions were highly specific macroscopically and microscopically while reactions elicited by conjugates displayed considerable macroscopic and microscopic cross-reactivity. The greater cross-reactivity of conjugate-elicited reactions compared to contact reactions may reflect differences in mechanism of initiation or mediation of these two reactions.

Modulation of expression of delayed hypersensitivity by mycobacterial antigen 85 fibronectin-binding proteins

“…PPD and DNP-ovalbumin elicited no immediate or Arthus reactions of edema and erythema at 1 to 4 h and elicited typical erythematous DH reactions which were maximal at 24 h. hsp65 (100 ng) elicited no Arthus reactions in any animal and typical DH responses in 18 of 22 animals tested. These reactions were histologically similar to those elicited by PPD and displayed intense deep and superficial dermal mononuclear cell infiltrates and superficial dermal basophil infiltrates (17). In contrast, 100-ng doses of purified Ag85A(B), Ag85B(T), or Ag85C(T) elicited no immediate or Arthus reactions and only minimal delayed reactions (Table 2) lacking significant cellular infiltrates at injection sites.…”

“…PPD was purchased (RT52; Statens Seruminstitut). Preparation and purification of 2,4-dinitrophenyl (DNP)11-ovalbumin have been previously described (17). Purified plasma FN was purchased (New York Blood Center, New York, N.Y.).…”

“…), 400 ± 50 g at the time of sensitization, were injected in multiple sites with a total of 1 ml of Freund's complete adjuvant containing 1 mg of 1-thiocyano-2,4-dinitrobenzene (ICN Biomedicals, Costa Mesa, Calif.) and 1 mg of heat-killed mixed strains of human M. tuberculosis (Ministry of Food, Fisheries and Agriculture, Weybridge, United Kingdom) and were boosted by topical application of 1-thiocyano-2,4-dinitrobenzene multiple times (17). This sensitization protocol yields highly sensitized animals with typical DH responses to intracutaneously injected PPD and DNP-ovalbumin as judged by kinetics and histologic appearance (17). Skin tests on guinea pigs were performed by intracutaneous injection of test materials dissolved in 0.1 ml of sterile PBS.…”

“…DH reactions greater than 9 mm2 are considered significant. Punch biopsies (4 mm) of skin reactions were taken from ketamine-anesthetized animals, fixed in glutaraldehyde, embedded, and treated with Giemsa stain (17). Coded sections were evaluated independently by two observers (K.M.…”

“…and H.P.G.) for deep and superficial dermal cellular infiltrates (17). Deep dermal infiltrates were evaluated qualitatively on a scale of 0 to 4 (0, no infiltrate; 1, minimal infiltrate; 2, moderate infiltrate; 3, heavy infiltrate; 4, very heavy infiltrate and microabscesses).…”