Dendritic epidermal (gamma)/(delta) T cells (DETC) activated in vivo proliferate in vitro in response to Mycobacterium leprae antigens

• Published in: International journal of dermatology 2000-08, Vol.39 (8), p.603
• Main Authors: Kaminski, Marek J, Mroczkowski, Tomasz F, Krotoski, Wojeiech A
• Format: Article
• Language: English
• ISSN: 0011-9059; 1365-4632

BACKGROUND: gamma/delta T-cell receptor (TCR)+ dendritic epidermal T cells (DETC) are part of a primitive defense system in the skin; they are capable of responding only to a limited number of antigens. The aim of the present study was to test whether DETC can proliferate in vitro in response to antigens of Mycobacterium leprae. METHODS: DETC were obtained from CBA mouse ear skin by trypsinization and Histopaque gradient centrifugation. The resulting epidermal cell suspension contained up to 20% DETC, as analyzed by the fluorescence activated cell sorter (FACS) after staining with anti-Thy-1 or anti-gamma/delta TCR monoclonal antibodies (mAbs). The freshly isolated cells, or DETC cultured up to 4 weeks with interleukin-2 (IL-2), were exposed in vitro for up to 6 days to varying doses of the following M. leprae antigens: (1) integral (live) M. leprae bacilli; (2) Dharmendra antigen; and (3) PGL-1 (phenolic glycolipid of M. leprae). The DETC response was assessed by tritiated thymidine (3H-TdR) incorporation. RESULTS: The freshly isolated DETC, or DETC cultured up to 4 weeks with IL-2, did not respond significantly to any of the M. leprae antigens, although at the same time they were able to respond vigorously to concanavalin A (Con A), as positive control. If, however, DETC were isolated from skin, painted 7 days before with croton oil (10 microL/cm2 to cause irritant dermatitis, they were able to respond to all M. leprae antigens by a 3-4-fold incrase in the 3H-TdR uptake. The most effective stimulator was a 1 : 1 mixture of Dharmendra and PGL-1 (0. 01 microg/mL), which was as effective as 10-fold higher doses of either antigen alone. Cell counts confirmed that increased DNA synthesis was associated with cell proliferation. Experiments employing alpha/beta-TCR CBA murine spleen cells and epidermal cell suspension treated with anti-gamma/delta or antialpha/beta mAbs + C' proved that only the gamma/delta DETC were the responder cells to M. leprae antigens. CONCLUSIONS: The results suggest that activation of DETC in vivo may make them responsive to M. leprae antigens. A significant increase in the number of class II major histocompatibility complex (MHC) positive, nondendritic cells was observed in the croton oil-treated epidermis. We hypothesize that croson oil-induced upregulation of class II MHC expression, which endows epidermal cells with antigen-presenting capabilities, might be an important factor in vivo in delivering an immunogenic signal to resident