Immunohistochemistry of skin lesions in leprosy and leprosy reactions

Objectives: 1. To study the immunohistochemistry of leprosy granulomas in the skin biopsy specimens of patients with tuberculoid and lepromatous leprosy, with respect to the presence and arrangement of CD4þ, CD8þ and CD28þT cells, CD 68þ cells and CD1aþ cells. 2. To study the immunohistochemistry findings observed in leprosy reactions. Design: Descriptive study. Skin biopsies in which the clinical and histopathological diagnosis of leprosy was reported between 1.8.2016 to 31.5.2017 in the Government Medical College, Kozhikode, were selected for the study. Immunohistochemistry of the skin lesions in leprosy and leprosy reactions was studied, looking specifically for the distribution of CD4/ CD8/ CD28/ CD68/ CD1a positive cells in leprosy at different scenarios. Results: Twenty-six tuberculoid and 14 lepromatous cases were included in the study. All granulomas irrespective of disease type showed positive staining for CD4 and CD68. Two of the 14 lepromatous leprosy cases (14·3%), and 15/26 (57·7%) tuberculoid specimens manifested moderate to strong CD4 expression. CD28 negativity was documented in four tuberculoid (15·4%) and 10 lepromatous cases (71·4%). Moderate to strong CD4 expression was noted in more than 70% of upgrading T1R while a similar finding was documented in only 20%–50% of other groups. More than 80% of static and upgrading T1R showed CD28 positivity, which was higher than the 30%–50% positivity recorded in other groups. Conclusions: The observations of the current study indicate a role for immunohistochemistry analysis in delineating the complex immunological processes involved in leprosy and leprosy reactions.