Lysozyme as a measure of cellular dynamics in the lesions of leprosy

The levels and distribution of lysozyme-positive cells and exudate were studied in leprosy lesions through the spectrum, in untreated and treated patients, in relapse and in reactions. Altogether 124 skin biopsies were examined by the immunoperoxidase technique. Monocytes, neutrophil-polymorphs and mast cells were the most conspicuous cells seen. Lysozyme proved to be a useful means of indexing renewal of these cells in the lesions. Peak numbers of monocytes were seen in lesions of active lepromatous leprosy (LL) and of tuberculoid leprosy (TT), at poles of opposite immunological performance. In TT the stimulus for recruitment was delayed hypersensitivity (DH). A decline in DH from TT towards the middle of the spectrum, mid-borderline, was accompanied by a fall in monocyte level. Furthermore, reacting lesions due to enhanced DH also had increased numbers of monocytes. On the other hand reactions associated with immunological deterioration were similar to active lepromatous leprosy (LL) and monocyte influx was raised in response to the stimulus of free multiplication of bacilli in both cases. In TT delayed hypersensitivity acted also to promote the rapid transformation of monocytes to epithelioid and giant cells all of which were strongly positive for lysozyme. This was in contrast to much lower levels in histologically similar macrophage-epithelioid cells of BT granulomas. Lysozyme synthesis was not seen in macrophages after ingestion of M. leprae. Early foamy change was made conspicuous by lysozyme deposited in phagocytic vacuoles, but old foam cells in regressing lepromas were negative. Lysozyme bound to dead extracellular M. leprae but not to viable or intracellular organisms. Dead bacilli or immune complexes appeared to be the stimulus for neutrophil-polymorph recruitment, mainly in reactions.