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

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 DETC in the skin.

Lepromin responses in recipients of a candidate antileprosy bacterin vaccine (WHO-IMMLEP Mycobacterium leprae killed preparation) in the USA.

BACKGROUND: Identification of the nine-banded armadillo as a potential source of massive numbers of Mycobacterium leprae led to the development of a candidate bacterin vaccine for possible immunoprophylaxis. METHODS: Volunteers were from a leprosy-hypoendemic, nonBCG-using area (USA). They had been vaccinated intradermally 3 years earlier with a candidate antileprosy bacterin vaccine of irradiated and autoclaved Mycobacterium leprae obtained from experimental nine-banded armadillos. They were tested for dermal responsiveness to standard lepromin A. RESULTS: Values for induration and erythema appeared slightly greater for the vaccinated group; however, the differences were not statistically significant, indicating no appreciable 'anamnestic' effect on either Fernandez (early) or Mitsuda (late) reactions after 3 years. CONCLUSIONS: Because previous studies had demonstrated that administration of this bacterin produced no humoral changes, it now appears less probable that laboratory methods will be of much help in assessing even possible effectiveness of such vaccination.

Lepromin skin testing in the classification of Hansen's disease in the United States.

Hansen's disease, or leprosy, although a relatively uncommon disease in the United States, continues to be important because of its implications--physical, psychological, and social--for the patient. Prognosis and treatment of the disease are based largely on clinical classification, which ranges from the multibacillary "lepromatous" to the paucibacillary "tuberculoid" forms, depending on the patient's specific immune capabilities. Traditionally, skin testing with lepromins--suspensions of the etiologic agent of Hansen's disease, Mycobacterium leprae--have been used as adjuncts to clinical parameters for classification in endemic areas. However, these have not been systematically studied in the United States. This report describes the results obtained from skin testing 38 volunteers (22 patients and 16 uninfected persons) with standard lepromin preparations. These results support the adjunctive value of lepromins for clinically classifying Hansen's disease in our "hypoendemic" population.

Preliminary study of a Mycobacterium leprae bacterin vaccine in a human volunteer population in a nonendemic area.

Seventeen volunteers who had never resided in areas with significant transmission of leprosy (Hansen's disease) were inoculated intradermally with 1.5 X 10(8) killed, purified armadillo-derived Mycobacterium leprae in a standardized preparation being tested for possible vaccine use. The peak of local skin responses, consisting of induration with or without ulceration similar to the post-lepromin Mitsuda reaction, occurred between the 21st and 28th days after injection. The maximum mean induration diameter was 17.2 mm, the minimum, 6.1 mm. Sera tested with the ELISA technique revealed no humoral response to either the sonicated bacilli, M. leprae-specific phenolic glycolipid I antigen, or three semi-synthetic analogues reactive with lepromatous patients' sera. The dose of M. leprae inoculated appeared to be safe and without unacceptable reactions at the injection site. One volunteer developed a generalized skin rash parallel to the local reaction, but the relationship of the former to the inoculation was unclear.