HUMAN CUTANEOUS LEISHMANIASIS - ULTRASTRUCTURAL INTERACTIONS BETWEEN THE INFLAMMATORY CELLS AND LEISHMAN BODIES IN THE SKIN-LESIONS

The ultrastructural interactions between the inflammatory infiltrate a nd Leishman bodies (LBs) were described in skin lesions from 16 patien ts with acute cutaneous leishmaniasis. in early stages of the inflamma tion, the cellular infiltrate consisted of both undifferentiated and d ifferentiated (activated) monocytes (M), macrophages (Mc), multinuclea red giant cells (MNGC), plasma cells (PC), lymphocytes (Ly), and fibro blasts (Fi. In late stages, the infiltrate was in the form of tubercul ous granulomas consisted mainly of type I secretory, and type II vesic ular epithelioid cells (ECs), in addition to remnant of some inflammat ory cells seen in the early stages. The two types of ECs were found on ly in six patients. The activated M, Me and MNGC were often parasitize d by LBs. The parasites were enclosed within the host cell digestive v acuoles (DVs), or phagolysosomes, together with skin melanosomes which are known to have lysosomal effect. In the DVs, LBs either survived o r were killed and expelled from the host cell cytoplasm. This study sh owed, for the first time, that the melanosomes were apparently involve d in killing of the LBs possibly by increasing the fatal effects of th e DVs hydrolytic enzymes. Plasma cells were packed with large ''Russel l's bodies'' indicating a high cellular immunoglobulin activity. The l arge, granular lymphocytes were in close contact to the activated M, p ossibly to promote delivery of activation signals. The type I secretor y ECs contained mucin-like granules with electrondense cores. In late stages of inflammation, the type II vesicular ECs contained lysosomal granules, and were found together with the type I ECs in broken-down t uberculous granulomas. The type I secretory ECs were previously though t to produce a mediator, or ''granuloma factor'' which recruits undiff erentiated mononuclear cells to perpetuate the granulomatous process; while the type II vesicular ECs were thought to appear where the granu lomatous process in brought to an end, preceeding the healing by fibro sis.