Histology DNCB

According to most authors, and our studies, a 0.1% primary non-toxic solution of DNCB in acetone causes no macroscopically visible reaction and no histological alterations on the flank and the nipple of guinea pigs. 

The primary toxic reaction of DNCB has been histologically examined by various authors. Among others ... 

In all of our experiments we used, for the patch test, a solution of 0.1 DNCB in acetone. In the macroscopic and histological examinations of unsensitized guinea pigs this solution does not give any positive reaction but merely a temporary in-... 

It seemed also (de Weck and Brun, 1957) that the course of the reaction was slightly modified by the acanthosis. After 24 hours the lesions on the acanthotic nipples were clearly less significant. Nonetheless, the histological differences observed between the reactions on the flanks and nipples with or without acanthosis do not permit us to affirm that acanthosis plays a protective role against the triggering of an eczematous reaction in animals sensitized with DNCB. . . . But we should keep in mind that under certain conditions, acanthosis can have a protective effect relative to the primary toxic reaction (see p. 8). 

We then re-examined the histological preparations of the 70 guinea pigs sensitized to DNCB and tested in the usual manner we found no small subcorneal vesicles either on the flank or on the nipple. Hence, these small vesicles are rare in the eczema of the adult guinea pig. On the other hand, we have seen them rather frequently in new-born sensitized guinea pigs. (Fig. 15). 

After a single application of 0.1% DNCB in acetone, the histological examination of the nipple and the flank of unsensiti ed new-born guinea pigs, does not reveal anything in particular. 

Appearance of Histological Eczematous Reactions During Sensitization 25 Table 4. Appearance of histological eczematous reactions during sensitization DNCB)... 

Macher and Sennlaub (1963) also observed on 2 guinea pigs sensitized with DNCB typical histological pictures of eczema, whereas the macroscopic examination was completely negative. 

We then wondered if there would be a histological difference between the 2 tests, since, as we have seen, the infiltrate with the CA test in guinea pigs sensitized only to CA, is largely composed of eosinophils while the infiltrate of the test with DNCB in guinea pigs sensitized only to DNCB is composed largely of small round cells (lymphocytes). 

Macroscopically, Hitch (1953) reported no difference among guinea pigs sensitized with DNCB, some of which were treated by corticosteroids. Under histological examination the reaction of the treated guinea pigs appears weaker however, this difference is not significant. 

Macroscopically, the irradiated flank gives practically no responses, whereas the non-irradiated flank gives a positive reaction, as usual, to DNCB. Histological examination confirms the macroscopic observation (Maggiora, Lozeron, 1962). 

After 100 days, macroscopic and histological examinations prove that guinea pigs sensitized on the neck are still sensitive to tests (0.1% DNCB in acetone) on the flank. There is no spontaneous disappearance nor clear decrease in the degree of sensitization (Fig. 32). 

After 40 daily applications there is a slight desensitization, that is, the tests which are positive after 24 hours become negative after 48 hours, while they remain clearly positive in the control guinea pigs (guinea pigs sensitized to DNCB after 40 days of no treatment). Histological examination discloses no difference. 

The resemblance of the eczematous reactions of the guinea pig and man in the histological examination has also been remarked by several authors Bloch and Steiner-Wourlisch (1930) with primine eczema, Brunsting and Bailey (1935) with ragweed, Baer, Rosenthal and Sims (1956), Grimmer and Spier (1961) with DNCB etc. 

In our clinic, de Weck and Brun (1956) observed, by means of passive transfer of donor animals sensitized with picryl chloride (according to Chase s method by injection of Freund s adjuvant), a histological picture in the receiver animals showing dermal but no epidermal lesions. Grimmer and Spier (1961) however, succeeded in transfering sensitivity to DNCB from animals sensitized to DNCB (by epicutaneous application). This was confirmed by a histological examination which showed both dermal and epidermal lesions. Nevertheless, their method of sensitization was different from the one used by de Weck and Brun. 

Grimmer (1961) pointed out that if sensitization is carried out through the lymph nodes or the spleen, only a dermal reaction is obtained. Recently this has also been emphasized by Klaschka (1966). The histological picture is different according to the means of sensitization (DNCB) solely dermal lesions (sensitization by intravenous and intraperitoneal injections) or combined dermal and epidermal lesions (epicutaneous applications or intra-cutaneous injections). 

Groth, O. Studies on contact skin reactions and normal skin of passively sensitized guinea-pigs. 1. A histological study of test lesions in recipients after passive transfer of dinitro-chlorobenzene (DNCB) hypersensitivity with lymphoid cells. Acta Soc. Med. upsalien. 68, 193—214 (1963). 

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