Three monoclonal antibodies to antigen presenting cells in the rat with differential influence on cellular interactions

Nerve growth factor and proprotein convertases furin and PC7 in transected sciatic nerves and in nerve segments cultured in conditioned media: their presence in Schwann cells, macrophages, and smooth muscle cells

Synthesis of proteins such as nerve growth factor (NGF) is induced after nerve lesion. The NGF precursor (pro-NGF) requires a posttranslational processing by proprotein convertases to become active. In this report, we re-examine the localization of NGF protein and mRNA in injured nerve and show that the candidate pro-NGF convertases furin and PC 7 colocalize with NGF in non-neuronal cells in nerve. By Northern blot analysis, 1.5-kb and 1.3-kb NGF mRNAs were shown to be increased in distal and immediately proximal nerve segments on days 1, 4, and 14 after lesion; by Western blot analysis, NGF proteins of high molecular weight were detected after injury. In vivo, two phases of NGF immunopositivity were observed, in macrophages and perivascular cells shortly after lesion and in endoneurial cells on day 1 and 4. To identify the cells containing NGF, nerve segments were incubated in serum-containing medium with or without conditioning by white blood cells isolated from the circulation. Both hybridization and immunoreactivity signals for NGF were elevated after incubation of nerve segments for 4 hours in conditioned media, so that cells with NGF immunoreactivity could be identified by antibodies to specific cell markers. In these nerve fragments, Schwann cells, perivascular smooth muscle cells, and macrophages contained NGF immunoreactivity. The concentration of furin and PC7 mRNA also increased in lesioned nerves. By immunocytochemical investigation of nerve explants, furin and PC7 were detected in endoneurial cells, macrophages and perivascular cells and were colocalized with NGF. These in vitro and in vivo findings suggest that both furin and PC7 are associated with NGF in several cell types of the sciatic nerve and, hence, may be implicated in intracellular processing of pro-NGF.

Priming enhances endotoxin-induced thermal hyperalgesia and mechanical allodynia in rats

Central inflammation is an integral component and contributor of the pathology of many debilitating diseases and has been shown to produce spontaneous pain and hyperalgesia. Recently, administration of lipopolysaccharide (LPS) into the lateral ventricle of rats was shown to elicit both thermal hyperalgesia and tactile allodynia [K. Walker, A. Dray, M. Perkins, Hyperalgesia in rats following intracerebroventricular administration of endotoxin: effect of bradykinin B1 and B2 receptor antagonist treatment, Pain 65 (1996) 211-219]. In this study, we have replicated the LPS model with some adaptations and correlated the nociceptive behaviors with an increased expression of activated macrophages in the central nervous system. We also examined the effects of priming on LPS-induced decreases in thermal nociceptive thresholds and mechanical response thresholds following either central or peripheral administration. Intracerebroventricular (i.c.v.) administration of LPS (0.2 microgram/rat) did not alter either thermal (hot plate) or mechanical (von Frey filaments) thresholds compared to baseline values in the first few hours after injection. However, priming rats by pretreating with i.c.v. LPS (0.2 microgram) 24 h prior to testing with i.c.v. LPS (0.2 microgram) produced significant mechanical allodynia and thermal hyperalgesia. The mechanical allodynia had an onset of 80 min after injection and a duration of 5 h. A similar time course was observed for thermal hyperalgesia, although its expression was less pronounced. Immunohistochemical studies indicated an increased expression of activated macrophages in the brain parenchyma of primed rats but not in unprimed rats. Intraperitoneal (i.p., 2 mg/kg) administration of LPS had no significant effect on either thermal or mechanical thresholds in the first few hours after injection; however, priming rats via i.p. (0.2 mg/kg) or i.c.v. (0.2 microgram) LPS produced a reduction in both thermal nociceptive thresholds and mechanical response thresholds in rats given a subsequent i.p. injection of LPS. This study demonstrates that priming is an effective protocol for the induction of central inflammation and increases the duration of these behaviors after i.c. v. administration.

Pathogenesis of cyclosporin A-induced autoimmunity: absence of T-cell reactivity towards syngeneic antigen presenting cells

Cyclosporin A-induced autoimmunity (CsA-AI) is a T-cell mediated inflammatory autoimmune disease of the skin resembling human scleroderma and is often referred to as syngeneic-Graft-versus-Host Disease. Induction of CsA-AI is obtained by total body irradiation in combination with syngeneic bone marrow transplantation (BMT) and subsequent administration of CsA for 4 weeks; about 2 weeks after withdrawal of CsA disease develops. In CsA-AI, irradiation is thought to eliminate peripheral autoregulatory T-cells, whereas CsA interferes with selection in the thymus giving rise to putative autoreactive T-cells. MHC class II-self-peptide complexes have been thought to function as autoantigen(s). Moreover, induction of CsA-AI is used in humans to achieve a Graft-versus-Leukemia effect based on this anti-MHC class II reactivity. In this study we therefore have examined whether T-cells of CsA-AI rats respond to syngeneic dendritic cells (DC). Furthermore we determined the in vitro stimulatory capacity of the presumptive antigen presenting cell (APC) in the target organs, i.e. the keratinocytes. In contrast to keratinocytes of control rats the keratinocytes of CsA-AI rats show in situ a strong reactivity with anti-MHC class II specific monoclonal antibody (mAb) and therefore might induce local T-cell activation. Results reveal that T-cells of CsA-AI rats have no increased response to syngeneic DC. This indicates that MHC class II is not the autoantigen and that the autoantigen(s) are not presented by peripheral APC of control animals. With respect to possible APC in the target organ flow cytometry showed a strong induction of MHC class II and upregulation of MHC class I on keratinocytes of CsA-AI rats. However, these cells were unable to give any stimulatory signal to T-cells of control or diseased animals, indicating that the autoantigen(s) are not presented by keratinocytes of CsA-AI rats and that the MHC induction is probably secondary to the inflammatory reaction in the skin. The nature of the autoantigen(s) therefore remains to be determined.

Expression of CD43 epitopes on NK and T cells

CD43 epitope expression was studied with a panel of monoclonal antibodies (MoAbs) by immunohistochemistry on freeze sections of lymphoid tissues. The MoAb WEN3 stained most cells weakly in the T areas and scattered splenic red pulp cells strongly, whereas the other MoAbs strongly stained the majority of the cells in the T areas but gave variable staining patterns of cells in the non-T areas. Flow cytometry on CD4+ and CD8+ T cells (T4 and T8 cells), freshly isolated NK cells and LAK cells showed distinct staining profiles for each cell type, with epitope expression patterns of T8 cells lying between those of T4 cells and NK/LAK cells. T8 cells were split by one of the MoAbs, the NK cells, but not LAK cells, were split by two other MoAbs.