Correlation of the onset of experimental autoimmune encephalomyelitis-like clinical signs with oedema of the spinal cord in tunicamycin-poisoned rats

Concordance and localization of maximal vascular permeability change and fibrin deposition in the central neuraxis of Lewis rats with cell-transferred experimental allergic encephalomyelitis

This study utilized Lewis rats and the cell-transfer form of experimental allergic encephalomyelitis (EAE) to focus on two central nervous system microvascular alterations known to be intimately associated with early clinical neurological signs of the disease, namely increased vascular permeability and deposition of fibrin. The main objective of the work was to define the degree of concordance and the anatomical localization of maximal vascular permeability change and fibrin deposition within the neuraxis of recipient rats during the earliest expression of clinical manifestations of the disease. Recipients were injected with predetermined doses of activated, myelin basic protein (MBP)-reactive syngeneic donor lymphoid cells and killed 6 or 7 days later when they exhibited the first clinical signs of disease. This experimental design allowed assessment of late occurring immune activities of a single population of MBP-reactive effector cells. Increased vascular permeability, expressed as mean extravascular blood equivalents (EVBE), attained maximum change, i.e., 16.04 +/- 5.07, within the lumbosacrococcygeal segment of the spinal cord (LSC). Maximal density of fibrin depositions, i.e., 192 +/- 94 deposits, also occurred within the LSC cord. The concordance of these two histoimmunopathological events, their tight linkage to early clinical signs of disease and the fact that both events attained maximal values within the LSC cord suggest that increased permeability and activation of the coagulation cascade may be prerequisite events for the expression of neurological signs of EAE.

Multiple sclerosis brain immunoglobulins stimulate myelin basic protein degradation in human myelin: a new cause of demyelination

Membrane-bound proteolysis may be implicated in the pathogenesis of demyelinating disorders including multiple sclerosis (MS). We previously found that the extent of myelin basic protein (MBP) degradation by the calcium-activated neutral protease did not differ for isolated human control myelin or MS myelin. Hence we suggested that, if involved in demyelination, the myelin neutral protease must be activated in vivo by an increased availability of free calcium. The postulate was therefore tested that immunoglobulin (Ig) binding to myelin results in activation of the myelin neutral protease, possibly through release of free calcium from calcium-binding sites of myelin. Isolated myelin from the brains of controls and patients with MS were incubated with purified Igs eluted from the brains of patients with MS or controls and degradation of MBP was assessed by quantitative electroimmunoblotting. Such degradation was significantly greater in myelin incubated in the presence of MS Igs than in myelin incubated without added Igs or in the presence of control Igs. Furthermore, the degree of MBP degradation in myelin incubated with control Igs was similar to that observed in myelin incubated without added Igs. Accordingly, it is suggested that Ig in MS brain potentiates myelin breakdown. Moreover activation of membrane-bound proteolysis by Ig binding to myelin appears to represent a hitherto undescribed pathway for demyelination in MS.

Developmental study of myelin basic protein variants in various regions of pig nervous system

A developmental study of myelin basic protein (MBP) variants in eight regions of pig nervous system (NS) was performed using a quantitative electroimmunoblotting procedure. Four major MBP forms with apparent molecular weights of 21.5K, 20.2K, 18.5K, and 17.3K were identified in both the CNS and the PNS and were detected as early as 22 days before birth. Quantification of the most abundant forms, the 21.5K and 18.5K MBPs, revealed characteristic profiles of accumulation of these two variants in different regions of the NS. The ratio of 21.5K:18.5K MBP varied with developmental time as well as with the various NS regions, peaking 20 days postnatally. The 17.3K MBP was observed from embryonic stages to adulthood, as were the 21.5K and 18.5K forms. In contrast, the 20.2K variant appeared most abundant from 10 days before to 22 days after birth and thereafter decreased in intensity so as to be no longer detectable in the brain of a 5-year-old pig. A similar pattern was also observed with an anti-MBP-reacting protein with an apparent molecular weight of 23K. Taken together, these results suggest that in the pig NS, the expression of MBP variants may be regulated both regionally and developmentally.