Cellular infiltrate in situ and response kinetics of human intradermal and epicutaneous tuberculin reactions

Monoclonal antibodies used in the avidin-biotin-peroxidase complex (ABC) method and a histochemical azo-dye method for acid α-naphthyl acetate esterase (ANAE) were used to identify T lymphocytes and their functional subpopulations, B cells, and mononuclear phagocytes in tuberculin-test reactions. At 6 and 24 hr up to 52% of all dermal inflammatory cells in situ were T6+, whereas at 72 hr no T6+ cells were observed in the dermis. This suggests that in the initial phases of tuberculin reactions the epidermal Langerhans cells are mobilized to the perivascular spaces in the dermis. At 6, 24, and 48 hr T3+ T lymphocytes usually formed the main inflammatory cell type in situ. The high proportion of Ia+ T lymphocytes and the variations in the local proportion and numbers of T4+ and T8+ cells suggest that T cells play an active role in the generation of a positive tuberculin reaction. At 72 hr T-pattern ANAE+ lymphocytes accounted for 64 ± 9 and 35 ± 10% of all cells in situ in epicutaneous and intradermal tuberculin reactions, respectively ( P < 0.05). The corresponding values for M-pattern ANAE+ macrophages were 27 ± 9 and 53 ± 10% ( P < 0.10). This indicates that the recruitment of mononuclear phagocytes is delayed if tuberculin is applied epicutaneously rather than injected intradermally.