Contact sensitivity to DNCB in normal and cell-mediated-immunity deficient chickens: in vivo detection and correlation with lymphocyte transformation and graft-versus-host reaction.

Optimum conditions for the contact sensitivity (CS) test using 2,4-dinitrochlorobenzene (DNCB) were sensitization with 0.25 ml of a DNCB solution (10 mg/ml) and challenge with one-tenth of this dose two weeks later. This produced reaction in terms of skin thickness which could be easily observed and measured. The cutaneous hypersensitivity developed slowly, reaching its maximum manifestation after 24 h of challenge and gradually declining thereafter. The development of a skin reaction was typical of delayed type hypersensitivity and was characterized histopathologically by congestion, oedema, mononuclear and heterophilic cell infiltration in the dermal layer and lymphocytic perivascular cuffing. The efficiency of the CS test was compared with that of the lymphocyte transformation (LT) test and graft-versus-host (GvH) reaction for monitoring cell-mediated immunity (CMI) in normal and CMI deficient chickens. CMI deficient chickens were prepared by neonatal thymectomy and inoculation of antithymocyte serum. The CMI response of deficient chickens was significantly less (p less than 0.01) as determined by all three tests. The percentage decrease in response to mount GvH, CS and LT was 88.9, 58.3 and 74.6, respectively. All the tests were found to be equally effective in assessing CMI response in chickens as determined by comparing the means of their performances.