Immunological implications of necrotic, cellular and vascular changes in leprous neuritis: light and electron microscopy.

Su mmary. The fine structural changes and, to a lesser extent, histochemical and histopathological features of biopsy specimens of nerves from patients with non-lepromatous leprosy ( mainly very early cases) , or lepromatous leprosy (mostly treated cases) , have been studied from the point of view of possible immunological response of the host tissues. Using electronmicro­ scopy and acid phosphatase or B-glucuronidase as markers of lysosomal enzymes , the survival and degradation of Mycobacterium leprae by Schwann cells and macro phages in the nerves is compared, both these cells utilizing the lysosomal machinery for such degradation , the macrophages more strongly , once the individual bacillary space has been breached . Long­ treated lepromatous patients show relatively fewer intact and more degener­ ating bacilli . Both live and killed M. leprae appear to provide antigenic material , and plasma cells as well as activated macrophages harbouring considerable rough ER, probably produce antibodies and lysosomal enzymes. I mpressive , fine structural changes in clinically well-preserved nerves from patients with very early non-lepromatous leprosy, as well as those with overtly tuberculoid and untreated or treated lepromatous leprosy, included the appearance of products of breakdown of nerve fibres, particularly of myelin , vacuolated macro phages among the fibres ; and changes in the intra­ neural blood vessels such as loosening of the endothelial-tight junctions, proliferation of basement membrane and exudation of plasmatous material perivascularly . On the basis of these findings 3 possible non-bacterial antigens producing damage to nerve parenchyma are considered : (i) myelin­ ogenous proteins which are known to evoke allergic neuritis and further