Does high mobility group 1 protein function as a late mediator for LPS- or TNF-induced shock in galactosamine-sensitized mice?

The role of high mobility group-1 protein (HMG-1) in LPS- and TNF-a-induced lethal shock in galactosamine (GalN)-sensitized mice was investigated. No detectable HMG-1 levels were observed by immunoblotting analysis in plasma from untreated or GalN-sensitized BALB/c mice 5 h after LPS injection, although significant levels of HMG-1 were detected in plasma 6 h after the challenge. All GalN-sensitized BALB/c but not BALB/lpsd mice succumbed by 6 h after LPS injection. When GalN-sensitized mice were injected with TNF-α, the presence of HMG-1 was seen at 5.5 h in plasma of BALB/c mice and at 6 h in BALB/lpsd mice, although almost all GalN-sensitized BALB/c mice died by 6 h after challenge. The time-dependent phenomenon correlated with elevated serum aspartate aminotransferase (AST) levels and the appearance of apoptotic cells in livers. Administration of pooled plasma, equivalent to approximately 200 μg recombinant murine HMG-1, taken from mice on the verge of near death, did not result in induction of lethal shock in GalN-sensitized mice. Taken together with the late appearance of HMG-1 in moribund mice, these data suggest that HMG-1 does not decisively contribute to lethality in the GalN sensitization model.

Induction of autoimmune gastritis by neonatal thymectomy requires autoantibodies and is prevented by anti-FcγR antibodies

The autoantibodies (auto-Abs) that are a hallmark of neonatally thymectomized (NTx) mice with autoimmune gastritis (AIG) have been poorly explored. We investigated their immune significance using B cell-deficient (B(-)) mice and found that B(-) mice are totally resistant to AIG but become susceptible to AIG after receiving bone marrow cells from B(+) mice. This susceptibility is most likely caused by the production of auto-Abs by B cells because B(-) pups also became susceptible to AIG when nourished by an AIG dam producing auto-Abs of the IgG class during the suckling period. NTx B(-) mice receiving purified IgG auto-Abs at this developmental stage similarly developed AIG. Auto-Abs probably act on antigen handling for antigen presentation because the treatment of NTx B(+) mice with anti-FcγR Abs prevented the development of AIG. Auto-Abs are indispensable for AIG development but are not sufficient because auto-Ab treatment did not increase AIG incidence in NTx B(+) mice above the baseline.

Different pathological phenotypes of autoimmune gastritis induced by neonatal thymectomy between BALB/c and (BALB/c x DBA/2) F1 mice: role of eosinophils in hypertrophic autoimmune gastritis

BACKGROUND

A unique pathological feature of murine autoimmune gastritis (AIG) is its pronounced mucosal hypertrophy, which is different from human type A chronic atrophic gastritis with pernicious anemia. The aim of this study was to clarify the mechanism of gastric hypertrophy in murine AIG, especially in relation to inflammatory cells infiltrating the gastric mucosa.

METHODS

Neonatally thymectomized (NTx) BALB/c and (BALB/c x DBA/2) F1 mice with gastritis were examined histologically and serologically. The T-helper (Th1/Th2) immune balance in the spleen was evaluated by intracellular cytokine staining for interferon-gamma and a flow-cytometric beads array for several cytokines. Additionally, NTx AIG BALB/c mice were orally administered an H(2)-blocker to decrease eosinophils.

RESULTS

NTx AIG BALB/c mice exhibited gastritis without stomach hypertrophy at 2 months of age, and developed gastritis with mucous gland hypertrophy accompanied by eosinophil infiltration at 6 months of age. In contrast, NTx AIG (BALB/c x DBA/2) F1 mice displayed gastritis with neither stomach hypertrophy nor eosinophil infiltration even at the age of 6 months. Upregulation of interleukin-4 and granulocyte-macrophage colony-stimulating factor in the spleen was observed in BALB/c mice but not in (BALB/c x DBA/2) F1 mice. Additionally, some NTx AIG BALB/c mice did not show gastric hypertrophy or eosinophil infiltration owing to the administration of an H(2)-blocker.

CONCLUSIONS

There are two different pathological phenotypes of murine AIG, chronic gastritis and hypertrophic gastritis, in NTx AIG BALB/c mice. Furthermore, eosinophil infiltration and the Th2 immune response might play a key role in the phenotypic shift from chronic gastritis to hypertrophic gastritis in these mice.