Studies on the contact sensitization of man with simple chemicals. II. Lymphokine production in allergic contact dermatitis to dinitrochlorobenzene

Contaminants of dinitrochlorobenzene

DNCB (2,4-dinitrochlorobenzene) is used in the treatment of alopecia areata, recalcitrant verrucae, and for evaluating immunocompromised patients. Currently, there is no pharmaceutical grade of DNCB available for clinical use. Recently, no nitrochlorobenzene contamination was found with the use of positive ion detection gas chromatography--mass spectrometry. We examined six commercial sources of DNCB, with the use of negative ion detection gas chromatography--mass spectrometry, for volatile impurities such as nitrochlorobenzene which might remain from the manufacturing process. The use of negative ion detection increases the sensitivity of this technic to benzene rings substituted with electron withdrawing groups like the nitrochlorobenzenes. We found that all sources of DNCB contain various combinations of nitrochlorobenzene, dinitrobenzene, nitrodichlorobenzene, and other isomers of DNCB. Nitrochlorobenzene has been shown to be mutagenic in the Ames test and carcinogenic in animal studies. The presence of nitrochlorobenzene and other contaminants in commercial grades of DNCB raises questions about the continued clinical application of this agent.

The role of mononitrochlorobenzene as a contaminant in dinitrochlorobenzene

Dinitrochlorobenzene (DNCB) has been purported to possess potential mutagenic and carcinogenic hazards. This potential hazard may be due to contamination of DNCB with known carcinogenic precursors, mononitrochlorobenzenes. Three samples of commercially available DNCB were analyzed for the presence of such mononitrochlorobenzenes, which were absent in all samples tested. The implications of product contamination with mutagenic and/or carcinogenic impurities may be important for both in vitro Ames microbial assays and potential carcinogenic exposure in human therapy.

In vitro DNA synthesis in lymphocytes from guinea pigs epicutaneously sensitized with DNCB

Lymph node lymphocytes from guinea pigs sensitized with the hapten homogenized in Freund's complete adjuvant or pretreated with cyclophosphamide shortly before an epicutaneous sensitization are capable of responding in vitro to a larger set of antigenic preparations than the lymphocytes from only epicutaneously sensitized animals. This may be due to a formation of a larger set of antigenic determinants when the hapten was homogenized in Freund's complete adjuvant or to a formation of a larger repertoire of lymphocytes capable of recognizing these determinants as it might be the result of pretreatment with cyclophosphamide. These procedures may also change the proportion of responding cells in the lymphocyte suspensions.

Detection of hapten erythrocyte conjugates in vitro and in vivo

The studies presented demonstrate that immunofluorescent techniques are capable of detecting picryl chloride erythrocyte protein conjugates formed in vitro and in vivo, following infusion of picryl chloride into normal, sensitized and tolerant guinea pigs. These experiments and the finding that picryl erythrocyte stromata prepared in vitro, and in vivo from infused recipients, have the capacity fo sensitize fresh animals, support the view that infused picryl chloride conjugates with the red cell membrane in vivo.

Studies on the contact sensitization of man with simple chemicals. IV. Timing of skin reactivity, lymphokine production, and blastogenesis following rechallenge with dinitrochlorobenzene using an automated microassay

An automated microassay was adapted to the sutdy of specific in vitro lymphocyte transformation to dinitrochlorobenzene (DNCB) erythrocyte complexes (DNCB-antigen). Studies of culture conditions indicated that in flat-bottomed microtiter culture plates, 0.2ml culturese containing 4x105 leukocytes and a total culture time of 4 or 5 days yeild satisfactory results for the relatively low responses seen with specific antigens such as DNCB-antigen. Culture were incubated for 3 hr with tritiated thymidine and harvested with the Multipe Automated Sample Harvester(MASH II). The effect of DNCB rechallenge on in vitro lymphocte transformation was stuided using this automated microassay. DNCB rechallenge boosted the in vitro response to DNON 25 TO 31 MM Hg; four patients (hypercapnic, group II) at a co2 from 54 to57 mm Hg. AH 8165 0.25 mg/kg (one quarter of the dose required for intubation) was given by rapid central venous injection. Haemodynamic responses were similar in the two groups; these were increase in heart rate ranging from 45 to 60 percent, increases in mean arterial pressure of 17-20 pre cent, and increases in cardiac output of 22-32 per cent. The intensity of neuromusclar blockade of the forearm muscles after AH 8165 was similar in the two groups, and there was no significant difference in recovery rates; roup I patients were 80 per cent recovered in 36.6 min, group II patinets in 47.3 min. It was concluded that the activity of AH 8165 was not influenced by moderate changes in respiratory acid-base status.

Studies on the contact sensitization of man with simple chemicals. III. Quantitative relationships between specific lymphocyte transformation, skin sensitivity, and lymphokine activity in response to dinitrochlorobenzene

Dinitrochlorobenzene (DNCB) coupled to peripheral blood erythrocytes or leukocytes forms a particulate complex, DNCB-antigen. The addition of DNCB-antigen induced blastogenesis and DNA synthesis in leukocyte cultures from DNCB-sensitized human subjects and not in leukocyte cultures from nonsensitized controls. In general, sensitized subjects who displayed a higher degree of cutaneous reactivity to DNCB, as manifested by duration and intensity of dermatitis, also showed a greater blastogenic response to DNCB-antigen in vitro. This quantitative correlation, however, was not invariant. Certain soluble factor(s), or lymphokines are released following the addition of DNCB-antigen to leukocyte cultures prepared from some sensitive subjects who were rechallenged one or more times with DNCB. These lymphokines induce blastogenesis in secondary target leukocyte populations from nonsensitized subjects. Extended studies are presented which slow little or no lymphokine activity in peripheral blood leukocyte cultures during a primary immune response, despite high degrees of blastogenic activity in response to DNCB-antigen. Significant lymphokine activity was observed only following additional rechallenge with DNCB. Blastogenesis and skin reactivity specific for DNCB have been shown to develop at about the same time during a primary immune response. This, along with the quantitative correlation shown in this communication, suggests that both processes probably reflect thymic-dependent cellular immunity. The appearance of lymphokine activity following rechallenge with DNCB suggests that DNCB-induced lymphokines may represent an amplifying mechanism of the cellular immune response that involves recruitment of previously uncommitted lymphocytes.