Immunohistological analysis of in situ expression of mycobacterial antigens in skin lesions of leprosy patients across the histopathological spectrum. Association of Mycobacterial lipoarabinomannan (LAM) and Mycobacterium leprae phenolic glycolipid-I (PGL-I) with leprosy reactions.

The presence of mycobacterial antigens in leprosy skin lesions was studied by immunohistological methods using monoclonal antibodies (MAbs) to Mycobacterium leprae-specific phenolic glycolipid I (PGL-I) and to cross-reactive mycobacterial antigens of 36 kd, 65 kd, and lipoarabinomannan (LAM). The staining patterns with MAb to 36 kd and 65 kd were heterogeneous and were also seen in the lesions of other skin diseases. The in situ staining of PGL-I and LAM was seen only in leprosy. Both antigens were abundantly present in infiltrating macrophages in the lesions of untreated multibacillary (MB) patients, whereas only PGL-I was occasionally seen in scattered macrophages in untreated paucibacillary lesions. During treatment, clearance of PGL-I from granulomas in MB lesions occurred before that of LAM, although the former persisted in scattered macrophages in some treated patients. This persistence of PGL-I in the lesions paralleled high serum anti-PGL-I antibody titers but was not indicative for the presence of viable bacilli in the lesions. Interestingly, we also observed a differential expression pattern of PGL-I and LAM in the lesions of MB patients with reactions during the course of the disease as compared with those without reactions. In conclusion, the in situ expression pattern of PGL-I and LAM in MB patients may assist in early diagnosis of reactions versus relapse.

Type 1- and type 2-like lesional skin-derived Mycobacterium leprae-responsive T cell clones are characterized by coexpression of IFN-gamma/TNF-alpha and IL-4/IL-5/IL-13, respectively.

In an earlier study, we generated a large number of Mycobacterium leprae-responsive and M. leprae-nonresponsive T cell clones (TCC) from the lesional skin of immunologic unstable borderline leprosy patients. In that study, we divided TCC into type 1- and type 2-like on the basis of their IFN-gamma and IL-4 expression. To explore whether other cytokines are coproduced along with IFN-gamma and IL-4, we investigated the secretion of a panel of other cytokines (TNF-alpha, IL-5, IL-6, IL-10, and IL-13) by a large number of these TCC. Upon analysis of 139 M. leprae-responsive TCC, we observed a positive correlation in the coproduction of IFN-gamma/TNF-alpha (r = 0.81), and in that of IL-4/IL-5 (r = 0.83), IL-4/IL-13 (r = 0.80), and IL-5/IL-13 (r = 0.82). Polarized type 1-like TCC produced dominantly IFN-gamma/TNF-alpha, and polarized type 2-like TCC predominantly IL-4/IL-5/IL-13. Most type 0-like TCC produced both sets of cytokines. In contrast, type 1- and type 2-like subsets of M. leprae-nonresponsive TCC (n = 58) did not show the same coexpression of these cytokines. Furthermore, when the differential expression of a broad panel of cytokines by individual M. leprae-responsive TCC is considered, it appeared that additional phenotypes could be recognized. These results suggested that distinct isotypes of type 1- and type 2-like T cells, based on the secretion of a panel of cytokines, may reflect M. leprae-specific characteristics.

Reversal reaction in borderline leprosy is associated with a polarized shift to type 1-like Mycobacterium leprae T cell reactivity in lesional skin: a follow-up study.

Borderline leprosy patients often undergo acute changes in immune reactivity that manifest as reversal reaction (RR) in the course of the disease. RR is associated with an exacerbated local delayed-type cellular immune response to Mycobacterium leprae and is responsible for severe tissue damage. We investigated whether RR episodes are associated with a change in T cell subsets in the lesional skin with regard to their cytokine secretion profiles. M. leprae-responsive T cell lines and thereafter T cell clones (TCC) were generated from the lesional skin of seven untreated borderline leprosy patients (with or without RR) and again from three of these patients experiencing RR during treatment. The phenotypes of the M. leprae-responsive TCC were either CD4+, CD8+, CD4-/CD8+/TCR gammadelta+, or CD4-/CD8-/TCR gammadelta+, although most of them were CD4+. Regardless of the clinical status of the untreated patients, a major subset of the M. leprae-responsive TCC was type 0-like and produced both IFN-gamma and IL-4. Interestingly, in all three patients who experienced a (re)occurrence of RR during treatment after the first analysis, a clear shift to polarized IFN-gamma production by the M. leprae-responsive TCC (type 1-like) was observed. This shift in T cell subsets was also reflected in the observed decrease in serum IgG and IgM levels of the same patients during RR. These finding indicate that CD4+ M. leprae-responsive T cells with a polarized type 1-like phenotype might be responsible for the immune-mediated tissue damage occurring during RR.