Recent evidence in animal models suggests that components of the extracellular matrix (ECM) play a primary role in peripheral nerve degeneration and regeneration.
We investigated the expression of ...several ECM molecules in human sural nerves by immunohistochemistry, Western blot, and reverse transcriptase PCR analysis. To unravel the possible role of these molecules in nerve regeneration, we compared results obtained from nerves with abundant signs of regeneration with those with complete absence of axonal regeneration. The role of some ECM components on neurite extension was further tested in dorsal root ganglion cultures.
We observed that the ECM composition significantly differs in regenerating compared with nonregenerating nerves, independently from their etiologic background. Fibronectin was abundantly expressed in regenerating nerves, whereas vitronectin and fibrin(ogen) prevailed in nonregenerating nerves. Whereas fibronectin is secreted by endoneurial cells, in vivo and vitro studies showed that the source of vitronectin and fibrin(ogen) is the bloodstream.
These data indicate that nerve regeneration is impaired in the presence of breaches in the blood-nerve barrier or impaired extracellular matrix (ECM) degradation that leads to accumulation of plasma vitronectin and fibrin(ogen). The transformation into mature, fibronectin-enriched ECM is necessary for efficient nerve regeneration in humans.
The identification of ricin toxin A‐chain (RTA) epitopes and the molecular context in which they are recognized will allow strategies to be devised that prevent/suppress an anti‐RTA immune response ...in patients treated with RTA‐based immunotoxins. RTA‐specific human T‐cell lines and T‐cell clones were produced by in vitro priming of PBMC. The T‐cell clones used a limited set of Vβ chains (Vβ1, Vβ2 and Vβ8) to recognize RTA epitopes. The use of RTA deletion mutants demonstrated that T‐cell lines and T‐cell clones from three out of four donors responded to RTA epitopes within the domain D124‐Q223, whereas one donor recognized the region I1‐D124. The response to RTA peptides of T‐cell lines and T‐cell clones from two donors allowed the identification of immunogenic segments (D124‐G140 and L161‐T190) recognized in the context of different HLA‐DRB1 alleles (HLA‐DRB1*0801, and HLA‐DRB1*11011 and B1*03011, respectively). The response to L161‐T190 was investigated in greater detail. We found that the HLA‐DRB1*03011 allele presents a minimal epitope represented by the sequence I175‐Y183 of RTA, whereas the HLA‐DRB1*11011 allele presents the minimal epitope M174‐I184. RTA peptides and an I175A RTA point mutant allowed us to identify I175 as a crucial residue for the epitope(s) recognized by the two HLA‐DRB1 alleles. Failure of T‐cell clones to recognize ribosome inactivating proteins (RIPs) showing sequences similar but not identical to RTA further confirmed the role of I175 as a key residue for the epitope recognized in the context of HLA‐DRB1*11011/03011 alleles.
Anti-Purkinje cell antibodies (APCA), believed to be markers of paraneoplastic cerebellar degeneration in females, have been identified in the serum of 3 men with subacute sensory neuronopathies and ...no evidence of tumors 5 years after the onset of the neurological signs. By indirect immunohistochemistry on sections of rat cerebellum and dorsal root ganglia, the patients' IgG bound to the cytoplasms of both Purkinje cells and dorsal root ganglia neurons. By western blot analysis on whole human cerebellum and whole human dorsal root ganglia homogenates, the IgG from 2 patients bound to a 62-kd protein in both homogenates and the IgG from 1 patient bound to a 110-kd protein in the cerebellum homogenate only. Yo autoantibody test was negative in all patients. Our study provides evidence that non-anti-Yo APCA may be associated with subacute sensory neuronopathies and are not necessarily markers of an underlying tumor. The previously described anti-Yo APCA has only occurred in females with cancer.
The molecular mechanisms necessary for remyelination by oligodendrocytes remain unexplored. We previously characterized a myelin basic protein promoter-lacZ (MBP-lacZ) transgene whose expression is ...regulated uniquely during development, and also in pathological situations, suggesting that it may be a useful reporter of molecular mechanisms during remyelination. As a first step toward creating a transgenic mouse model of remyelination, we cultured oligodendrocytes from these transgenic mice and showed that expression of MBP-lacZ appeared in parallel with a marker of oligodendrocyte maturation, galactocerebroside (GC). In addition, basic fibroblast growth factor blocked the expression of both MBP-lacZ and GC in these cells. Therefore, expression of MBP-lacZ reflects not only the developmental stage of oligodendrocytes, but also extrinsic influences on oligodendrocytes. These data suggest that MBP-lacZ may be a useful marker in transgenic mouse models of remyelination.
Evidence has been presented that oolemmal integrins and their ligands on spermatozoa may play a role in gamete interactions leading to fertilization. We previously demonstrated that vitronectin (Vn) ...could be extracted from fresh human spermatozoa and detected in Western blots, and Vn was observed on the surface of living, capacitated sperm by indirect immunofluorescence. In the present experiments, messenger RNA encoding Vn was detected in human testis poly (A+) RNA using Northern analysis, and Vn was localized within the acrosomal region of ejaculated sperm by immunoperoxidase and immunofluorescence staining. During the acrosome reaction, induced in capacitated spermatozoa by lonomycin, Vn was released into the medium in a calcium-dependent manner. Vn appears to be a specific product of intratesticular spermatozoa that is secreted during the acrosome reaction. These findings suggest that Vn is positioned to play a strategic role in gamete interactions leading to fertilization.
We describe three patients with chronic progressive polyneuropathy associated with IgA monoclonal gammopathy. Two patients had a prominent sensory neuropathy and one had a prominent motor neuropathy. ...Sural nerve biopsies showed axonal degeneration in all cases. In immunocytochemical studies patients' IgG immunostained axons. By Western immunoblot a band of IgG reactivity with an axonal protein of 66 kDa was found. No band of IgA and IgM were found. We suggest the possibility that the IgA monoclonal protein may act as a stimulating factor of preexisting B cell clones eliciting an immune reaction against nerve antigens.
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