Ultrastructural changes in blood vessels of peripheral nerves in leprosy neuropathy. II. Borderline, borderline-lepromatous and lepromatous leprosy patients

Bacterial infections

The organisms that produce bacterial infections of the nervous system in tropical regions are similar to those existing in the rest of the world. However, because of poor socio-economic conditions in the former areas, preventing the implementation of appropriate prophylactic and therapeutic measures, the incidence and course of these diseases may vary. In this paper the neuropathological appearances of the main bacterial diseases are reviewed and the main differences between those occurring in developed and developing countries emphasized. Despite great efforts by governments and communities, tuberculosis still remains a scourge in many countries and leprosy has not been eradicated from earth. Earlier optimism that antibiotics could finally put an end to syphilis have been dashed and the disease still persists. Moreover, the explosion of AIDS not only has produced a recrudescence of many of these diseases, but has also changed their clinical and pathological presentation.

Infectious Neuropathies

Peripheral neuropathies can result from several infective agents, ranging from viruses, especially retroviruses, to parasites and bacilli. Leprosy, which often is considered a disorder of the past, still is common in dome geographic areas, especially in Africa, South America, and Asia. An increasing number of cases of neuropathies occurs in patients who have HIV or Lyme disease. The important point is that all these neuropathies are treatable and often preventable.

Ultrastructural study across the leprosy spectrum

We have carried out a systematic ultrastructural study of the bacilli, the cell-mediated response in the host, and the dermal microvasculature in lepromatous (LL), borderline lepromatous (BL), and borderline tuberculoid (BT) types of active leprosy (eight cases). In the types of least resistance (LL and BL), macrophages with large cytoplasmic processes were observed; in addition, numerous peripheral vacuoles were found in BL. Mast cells were abundant and vascular alterations constant. BT macrophages showed more regular outlines and multivacuolated cytoplasms with plentiful rough endoplasmic reticulum. Giant cells were scarce. Bacilli, both isolated and in globi, were contained within the vacuoles and appeared constantly in macrophages and endothelial and Schwann cells in LL and BL. Conversely, in BT they were found singly, infrequently in the endothelial cells, and not at all in Schwann cells. Forms in the process of destruction or degradation were more common than intact forms, in which the symmetric outline of the membrane could be seen clearly.

Blood-nerve barrier: ultrastructural and endothelial surface charge alterations following nerve crush

Nerve crush results in an enhanced vascular permeability of the endoneurial vessels distal to the lesion. Vascular permeability at the blood-nerve barrier (BNB) to serum proteins is influenced by many factors, including anionic surface charge, endothelial vesicular transcytosis and the presence or absence of fenestrated vessels. Using mice and rats, the present ultrastructural investigation examined the effect of nerve crush (axonotmesis) on: (1) the distribution of endothelial anionic sites and (2) the appearance of fenestrations in endoneurial vessels after 4 and 14 day intervals as demonstrated with cationic probes. Transient anionic fenestrations developed in a minority of mouse endoneurial vessels in 4-day crushed nerves, but were not found in 14-day crushed nerves of mice nor in crushed nerves of rats. The known increase in the permeability of endoneurial vessels in rats and mice was not associated with reduced luminal labelling with cationic ferritin at physiological pH. At pH 2.0 the labelling of glycocalyx moieties (such as sialic acid) with cationic colloidal gold was disrupted in some epi- and endoneurial vessels of 4-day rats, but in a greater proportion after 14 days. The enhanced permeability of the BNB during degeneration and regeneration is related to the formation of anionic fenestrations in endoneurial vessels of mice and to the reduced and uneven distribution of endothelial glycocalyx moieties that are anionic at pH 2.0 in rats.

Asymptomatic nerve hypertrophy in lepromatous leprosy: a clinical, electrophysiological and morphological study

In order to learn more about early nerve lesions observed in leprosy, we performed a clinical, electrophysiological and morphological study in seven patients with untreated lepromatous leprosy, palpably enlarged radial cutaneous nerve and preserved sensation in the corresponding territory. The conduction velocity of the cutaneous radial nerve, which was decreased in all patients, did not significantly differ from that of a group of patients with lepromatous leprosy, hypertrophy of the radial cutaneous nerve and sensory loss. In contrast, the sensory action potential was significantly lower in patients with sensory loss, which demonstrates that axon loss is more important than demyelination in producing sensory loss. In all patients nerve enlargement was due to thickening of the epineurium and of the perineurium subsequent to inflammatory infiltrates and proliferation of fibroblasts and perineurial cells. In several fascicles, the inflammatory infiltrates and the infected cells infiltrated endoneurial connective tissue septa and blood vessels. Mycobacteria leprae were abundant in perineurial cells, fibroblasts, macrophages, Schwann cells and endothelial cells, and lymphocytic vasculitis present in all cases. The average density of myelinated fibres was 2600 SD 880 fibres/mm2 (control: 7700 fibres/mm2), with marked differences between individual fascicles, versus 420 fibres/mm2 in patients with nerve hypertrophy and sensory loss (range 0-2080 fibres/mm2). Single fibre preparations showed that segmental demyelination predominated in two patients, axonal degeneration in one, while inflammatory infiltrates and proliferation of connective tissue adhering to individual fibres were prominent in the others.(ABSTRACT TRUNCATED AT 250 WORDS)

The pathology of early leprous neuropathy

A qualitative and quantitative study was made of early changes in nerves from 10 patients with tuberculoid or lepromatous type of leprosy. Five nerve biopsies, taken from sites remote from skin lesions, were considered to be unaffected when examined by paraffin histology but showed abnormalities in semi-thin resin sections and by electron microscopy; 5 showed mild to moderate involvement by paraffin histology. Changes in 'unaffected' nerves in both types of leprosy included the presence of subperineurial oedema; occasional evidence of fibre regeneration, sometimes with atypical features; increased numbers of small myelinated fibres, possibly a consequence of axonal atrophy; a few thinly remyelinated fibres, probably due to secondary demyelination, and some loss of unmyelinated axons. In more affected nerves there was variable loss of axons, both myelinated and unmyelinated. Demyelination was not a conspicuous feature; there was evidence of axonal atrophy in some fibres. Similarities in some of the changes observed in tuberculoid and lepromatous types of leprosy suggest a common mechanism of nerve damage, at least in the early stages. The presence of abnormalities in nerves at a distance from skin lesions implies a more diffuse nerve involvement than might have been expected in both types of leprosy.

Mechanisms of pathogenicity in mycobacteria

The purpose of this article is to review current knowledge about the mechanisms of pathogenicity of mycobacteria. The following aspects of the problem are discussed: chemically-defined compounds implicated in the mechanisms of pathogenicity; location in the cell wall of these compounds and their biological activities; mechanisms of intracellular survival of pathogenic mycobacteria as compared to intracellular killing of non-pathogenic mycobacteria; and pathogenesis of mycobacterial infection. The future prospects in the elucidation of the mechanisms of pathogenicity and their possible application for a better control of mycobacterial diseases are briefly discussed.

Altered blood rheology in the pathogenesis of diabetic and other neuropathies

Although a substantial literature confirms the abnormal flow properties of diabetic blood, only in a few papers has the vasculitis of diabetic neuropathy been considered to have a hemorheological cause. It is proposed that the pathogenesis of nerve lesions involves an interaction between the specialized nerve vascular system and focal ischemic lesions resulting from rheologically induced stasis. The proposition is extended into other conditions with abnormal blood rheology such as hypothyroidism, uremia, dysglobulinemia, polyarteritis nodosa, and lepromatous leprosy. It is concluded that the treatment of such polyneuropathies should include an agent which would improve the flow properties of the blood.

The laminate capillary and its wall of multiple basement membranes

Cutaneous telangiectatic vessels from two cases of unilateral dermatomal superficial telangiectasia were shown under electron microscopy to be venular capillaries with thick walls composed of multiple basement membranes. We suggest that this special capillary structure, seen in a variety of telangiectatic and disease states, should be called the 'laminate capillary'.

Significance of lymphocytes and blood vessel changes for edema formation in polyradiculoneuritis

Human sural nerve biopsies of eight cases with acute, subacute and chronic polyradiculoneuritis were studied by means of immunohistochemistry to characterize the inflammatory infiltrates. In addition, the structural changes of the endoneurial blood vessels were examined by electron microscopy, since both factors are likely to contribute to disturbances of the blood-nerve barrier. By use of six monoclonal antibodies, it was shown that the inflammatory infiltrates in cases with more acute polyradiculoneuritis are predominantly recruited by Leu 3a- and Leu 4-positive T lymphocytes. In more chronic polyradiculoneuritis beside of few Leu 3a-positive and Leu 4-positive T lymphocytes also B cells occurred. Leu M3-positive macrophages were detected in all cases with fluoride myelin degeneration. Since immunoreactivity for antigens of the HLA-D-locus (Leu-HLA-DR and Leu 10) were present on the infiltrating mononuclear cells, it can be postulated that they represent active and immunocompetent cells. Ultrastructurally, the amount of pinocytotic vesicles in the endothelial cells of the endoneurial blood vessels was increased. Moreover, a prominent folding of the luminal and abluminal surface of vascular endothelial cells and diminution of the intercellular tight junctions were observed. These findings appear suitable to explain the increased leakage of serum proteins across the blood-nerve barrier in polyradiculoneuritis sharing general features of cell-mediated immunity.

The leakage of serum proteins across the blood-nerve barrier in hereditary and inflammatory neuropathies. An immunohistochemical and morphometric study

The leakage of eight different serum proteins and immunoglobulins across the blood-nerve barrier (BNB) was studied by means of the peroxidase-antiperoxidase method in hereditary and inflammatory neuropathies and graded semiquantitatively with respect to endoneurial staining intensity and distribution. These data were compared with the degree of alterations of the myelinated nerve fibre population evaluated by morphometric analysis. Our series of 18 human sural nerve biopsies included seven hereditary neuropathies (three HMSN I, two HMSN II, two tomaculous neuropathies), nine inflammatory neuropathies (seven polyneuritis, two hypertrophic neuritis) and two normal controls. In HMSN II and in tomaculous neuropathy there was no enhanced endoneurial staining for serum proteins despite of a severe nerve fibre loss, whereas in HMSN I a rise of serum proteins of small and moderate molecular size like albumin and IgG was demonstrated in the endoneurial space indicating an impaired BNB function. Qualitative changes of the BNB with leakage also of high molecular weight proteins were observed in polyneuritis and hypertrophic neuritis, irrespective of the degree of nerve fibre changes. Our results show that fibre loss and alteration of the BNB are not correlated. The unselective leakage of serum proteins through the BNB appears to be a characteristic change in inflammatory neuropathies leading to proteinous edema. With regard to the subperineurial accentuation of the endoneurial edema it will be discussed that the vascular diffusion barrier is more fragile than the perineurial diffusion barrier.

On the occurrence of the fenestrated vessels in Wallerian degeneration of the peripheral nerve

Ultrastructural studies were made on the distal segments of the mouse phrenic nerve after crush injury. In the control, endoneurium contained only unfenestrated capillaries. In the experiment, from day 2 to day 6, endoneurial capillaries occasionally showed fenestrations with the attenuation of its cytoplasm. At this stage, axonal degeneration and myelin breakdown became evident showing early stage of Wallerian degeneration. In addition, detachment of the neighboring endothelial cells concomitant with the invasion of macrophage was also observed. These findings were previously unobserved changes of the endoneurial endothelium in Wallerian degeneration. The significance of the early occurrence of fenestrae was discussed briefly.

Ultrastructural and histophysiological studies on the blood-nerve barrier and perineurial barrier in leprosy neuropathy

Onset and nature of ultrastructural changes in endoneurial vasa nervorum during the pathogenesis of leprosy neuropathy and possibly associated alterations in the "blood-nerve barrier" were investigated, together with perineurial barrier functioning, in mice infected 20-28 months previously with Mycobacterium leprae and in (ageing) non-infected mice. Barriers were tested by i.v. administration of markers (Trypan blue and ferritin) 1-4 days before killing the mice. Twenty-eight months after infection, histopathology of sciatic nerves was comparable to that seen in sensory nerves in clinically early human (borderline-) lepromatous leprosy. Schwann cells and endoneurial macrophages were bacillated, endothelia of endoneurial vessels not, and the perineurium rarely. Many infected mice and all (ageing) controls possessed ultrastructurally and functionally normal endoneurial vessels. Their continuous endothelium with close junctions had prevented marker passage, even when surrounding endoneurial tissue cells were quite heavily bacillated. The perineurium was also normal. By contrast, in infected mice showing hind limb paralysis serious histopathologic involvement and large globi of bacilli intrafascicularly in sciatic nerves, endoneurial blood vessels were abnormal. Open endothelial junctions, extreme attenuation, fenestrations, and luminal protrusions were all features comparable to neural microangiopathy encountered in leprosy patients (Boddingius 1977a, b). The "blood-nerve barrier" clearly had become defective allowing excessive exudation of Trypan blue and ferritin, via four pathways from the vessel lumen, deep into surrounding endoneurial tissues but halted by a normal perineurial barrier. Markers in such "blue" nerves were not found in bacillated or non-bacillated Schwann cells, thus denying significant phagocytotic and lysosomal activities of Schwann cells at this stage of neuropathy. Possible implications of barrier performances for anti-leprosy drug treatment of patients are discussed.

Intracellular location of Mycobacterium leprae in macrophages of normal and immune-deficient mice and effect of rifampin

Soon after more than 10(6) Mycobacterium leprae, freshly harvested from armadillo liver or harvested and 60CO irradiated, were inoculated into the hind footpads of either normal or thymectomized and irradiated (T900R) mice, the organisms were found to reside within phagosomes of polymorphonuclear and mononuclear cells. On the other hand, 7 and 8 months after 10(4) freshly harvested M. leprae were inoculated into the footpads of normal or T900R mice and the organisms had multiplied to their maximum in the normal mice, many organisms, largely intact by electron-microscopic criteria, were found to reside free in the cytoplasm of the footpad macrophages, whereas damaged organisms were contained within phagosomes. After 11 months, many intact organisms were found to lie free in the cytoplasm of the macrophages of T900R mice, whereas only damaged intraphagosomal M. leprae cells were observed in the macrophages of normal mice. Finally, a remarkably large proportion of damaged extraphagosomal M. leprae was found in T900R mice administered rifampin for 2 days in a bactericidal dosage. It appears that M. leprae multiplies free in the cytoplasm of the footpad macrophages of infected mice, whereas the M. leprae cells resident within the phagosomes of the macrophages are dead. As the result of treatment with rifampin, the organisms appeared to have been killed in their extraphagosomal location, only afterwards being incorporated into phagosomes. However, the intracellular site in which M. leprae is killed in the course of an effective immune response remains unclear.

Pathology and pathogenesis of predilective sites of nerve damage in leprous neuritis. Nerves in the arm and the face

A very brief review of the literature on the clinicopathological aspects of leprosy is given; mainly through references. The salient features of the two main types of leprosy--tuberculoid and lepromatous--are presented in a Table. The surgical and pathological findings are briefly described and the pathogenesis of involvement of the facial nerve (a motor nerve) is discussed. On the basis of (i) the severe histopathologic changes (degeneration) of the most distal part of the zygomatic branch of the facial nerve (innervating the orbicularis oculi), with sparing of the roots of all branches and the trunk of the nerve; (ii) the concurrent loss of cutaneous sensations in the territory of the maxillary division of the trigeminal nerve (the region of the zygoma and the lower eyelid); and (iii) the close approximation or even anastomoses occurring between the ultimate branches of these two nerves, it is postulated that paralysis of orbicularis oculi occurs secondarily to the sensory nerve damage, i.e. due to spread of infection from the sensory branches of the trigeminal to the motor branches of the facial nerve. The surgical and pathological findings of the nerves in the arm, especially the ulnar and the median and their branches are described, in tuberculoid and lepromatous leprosy. The forms of nerve degeneration, the occasional axon regeneration, and the role of the Schwann cell in harbouring the bacilli, are illustrated. The lysosomal enzyme activity in the Schwann cells of nerve fibres, particularly of unmyelinated fibres which preferentially phagocytose the M. leprae, and their role, albeit not very successful, in degrading the bacilli and controlling the infection, are also stressed, through light and electronmicrographs. The constellation of secondary factors of the terrain operating to produce further damage to primarily diseased nerves, is discussed. These factors include indirect compression from unyielding fibroosseous tissues, minor traumata, stretching of the nerves, and their exposure to lower temperatures in subcutaneous tissues.

The Hoffmann reflex of the soleus muscle. A study in leprosy

The H reflex of the soleus muscle was used to investigate the monosynaptic reflex arc of two groups of leprosy patients compared with a similar group of normal subjects. The H reflex recordings show two abnormalities: (1) An increase in the latency of the reflex without difference between lepromatous and borderline patients. (2) A decrease of the Hmax:Mmax amplitude ratio more pronounced in the lepromatous group. The discrepancy between these results and the commonly described preservation of the deep tendon reflexes in leprosy is discussed and the hypothesis that leprosy neuropathy would affect all nerve trunks related to blood vessel changes in suggested.

Importance of the neural predilection of Mycobacterium leprae in leprosy

It is suggested that continuous leakage of bacilli into the circulation from a primary focus of intraneural infection may simultaneously initiate bacillary dissemination and the suppression of cell-mediated immunity. Both these features are essential for the development of lepromatous leprosy. Nerve involvement in leprosy, previously thought of as a diagnostic feature of the disease and as a complication of therapy, may represent an essential phase in the cycle of infection and reinfection by Mycobacterium leprae.

Fenestrated blood vessels in human skeletal muscle

In a fine structural study of 32 skeletal muscle biopsies, rare examples of fenestrated blood vessels (FV) were found in three cases. In view of similar observations reported in a case of Duchenne muscular dystrophy, it is suggested that FV albeit rare may occur in skeletal muscle at least under pathologic conditions. These aberrant FV may be derived from adjacent dermis and/or epineurium which are known to contain occasional FV. Alternatively, the occurrence of fenestrae may reflect a nonspecific alteration in pre-existing continuous endothelium. The significance, if any, of their presence in skeletal muscle is unknown.

Surface markers on lymphocytes and cells of the mononuclear phagocyte series in skin sections in leprosy

E, EA and EAC rosetting techniques and Ig fluorescence were used in a study of receptor sites in cryostat sections of lesions through the spectrum of leprosy, and for comparison in some other mycobacterial and granulomatous lesions. Anti-C3, and trypsin were used as blocking agents. Lymphocytes in borderline lepromatous leprosy produced EA adherence and IgG fluorescence indicating B type cells. Lymphocytes in tuberculoid leprosy produced neither E or EA adherence and no fluorescence; these cells were presumed to be T cells. EAC and EA adherence was more marked in areas of macrophage infiltration, where there were few lymphocytes, than over the lympocytes themselves. Two distinct patterns emerged: (i) EA binding together with IgG fluorescence was seen in active lepromatous leprosy and could be localised to the surface of individual macrophages, and (ii) EAC binding together with IgM fluorescence was seen in the granuloma of tuberculoid leprosy and sarcoidosis, but could not be definitely related to cell surface; rather it was diffusely spread over the whole granuloma; EAC adherence was diminished by anti-C3 serum. Trypsin removed EA binding completely, but only diminished EAC adherence. It is suggested that the EA pattern indicates immunoglobulin receptors on macrophage and lymphocyte surfaces: and that the EAC binding (which is stronger than EA) involves C3 and IgM receptors at extracellular sites as well as C3 receptor sites on epithelioid cell surfaces. EA and EAC binding were enhanced in borderline tuberculoid leprosy in reaction and erythema nodosum leprosum, suggesting that immunoglobulin and complement receptor sites increase in number with enhanced hypersensitivity.

Ultrastructural changes in blood vessels of peripheral nerves in leprosy neuropathy. I. Tuberculoid and borderline-tuberculoid leprosy patients

Radial or superficial peroneal nerve biopsies of 6 patients with tuberculoid or borderline-tuberculoid leprosy and 6 control nerve biopsies were examined by electron microscopy. Endoneurial blood vessels showed histopathology in all the leprosy patients. Changes, in particular, involved the basement membrane in postcapillary venules and venules. Multilayered parellel basement membranes, with collagen and ground substance, formed a thick coat ("hyaline zone") around the vessels. It is suggested that the zone inhibits passage of nutrients and metabolites and, thus, contributes to or is the main cause of the local destruction of (unmyelinated) nerve fibres and the lack of nerve fibre regeneration observed in this type of leprosy. The perivascular zone, presumably, is produced by pericytes in response to defects in the "blood-nerve barrier" of endoneurial vessels. In granulomata of leprosy skin lesions, a perivascular zone was not present. The endothelium of endoneurial vessels, in affected nerves, generally was normal. Occasionally, however, gaps and fenestrations were seen and there were histological indications that leakage of blood plasma had occurred through the gaps and through the basement membrane of the endothelium. Occlusion of endoneurial vessels was found only in the oldest patient and the degeneration of nerve fibres generally observed thus is considered not to be caused by ischaemia. Histopathology in epi-and perineurial vessels was definitely less pronounced than in endoneurial vessels.