Reproducibility of histology in leprosy lesions.

The variability of three commonly used histological parameters in leprosy histology was examined within and between lesions on individual patients by taking two biopsies, either from opposing edges of the same lesion or from the edge of two separate lesions. There was little variation in granuloma fraction (GF), bacterial index (BI), or histological classification on the Ridley-Jopling scale between biopsies from opposing edges of the same lesion, but there was considerable variation in the GF between biopsies from the edge of different lesions. A lesser degree of variation was seen in the BI between different lesions, and there was little difference in histological classification between established lesions. Thus, it appears that local factors influence the size of the leprosy granuloma, but its histological composition and bacterial load are determined systemically.

Cytochemical reactions of human leprosy bacilli and mycobacteria: ultrastructural implications.

Leprosy bacilli harvested from freshly biopsied tissue from cases of lepromatous, borderline and histoid leprosy were, in conjunction with Mycobacterium lepraemurium and representative mycobacteria, examined cytochemically with and without their pyridine-extractable acid-fastness. Unlike the mycobacteria, unextracted leprosy bacilli failed to give a positive response to the periodic acid Schiff test or to take up Sudan black B, toluidine blue O, alkaline methylene blue or safranin O. Once their acid-fastness was removed with pyridine, leprosy bacilli were stained by all of the foregoing dyes except Sudan black B, under this condition they remained gram positive. While permanent loss of acid-fastness from leprosy bacilli always resulted in a loss of acid hematein-fixing material (Smith-Dietrich-Baker tests), the reverse was not true. Mild aqueous saponification, bromination, or sequential treatment with lipase and phospholipase D resulted in a loss of acid hematein-positivity but not acid-fastness. After pyridine extraction, bromination, or aqueous saponification, true mycobacteria lost neither their acid hematein-positivity nor their acid-fastness. The acid hematein-positive material and the acid-fastness of both leprosy bacilli and mycobacteria were lost after treatment with alkaline ethanol. These cytochemical findings are discussed in the light of what is known of the ultrastructure of leprosy bacilli and mycobacteria, and of the occurrence of a dl-3, 4-dihydroxyphenylalanine oxidase in leprosy bacilli but not in mycobacteria. An effort is made to explain the rather unique cytochemical properties of leprosy bacilli. Since pyridine-extractable acid-fastness (and acid hematein-positivity) serve to distinguish human leprosy bacilli from M. lepraemurium, one or the other, or both, are suggested as bases for differentiating these two organisms in animal experiments designed to show the in vivo propagation of human leprosy bacilli.

Elimination of the acid fastness but not the gram positivity of leprosy bacilli after extraction with pyridine.

Bacilli from a number of tissues excised from cases of lepromatous and borderline leprosy, unlike mycobacteria, were found to lose their acid-fastness after treatment with pyridine.