Masahiko Murata

Topographic study ofHelicobacter pylori and HLA-DR antigen expression on gastric epithelium

Helicobacter pylori and HLA-DR antigen expression on gastric epithelium, identified by an indirect immunoperoxidase staining method using monoclonal antibodies againstH. pylori and HLA-DR antigens, were studied topographically. Fitty-nine biopsy specimens from 41 patients who had neither gastric cancer nor peptic ulcers were examined.H. pylori was observed predominantly over or on the surface epithelium, while HLA-DR antigens were frequently expressed on the epithelium of the isthmus region. These observations led to the conclusion that there was no direct topographic association betweenH. pylori and epithelial HLA-DR expression. However, the frequency of HLA-DR expression inH. pylori-positive (28/29) specimens was significantly higher than that inH. pylori-negative (18/30) specimens (P<0.01). Furthermore, a greater number ofH. pylori was associated with a stronger expression of HLA-DR antigens (P<0.001). We conclude thatH. pylori is indirectly related to HLA-DR expression on gastric epithelium.H. pylori is the first microbial agent that has been suggested to be associated with epithelial HLA-DR expression in the human gastrointestinal tract.

Effects of Protein Meals on the Urinary Excretion of Various Plasma Proteins in Healthy Subjects

To examine whether hemodynamic changes in response to acute protein loadings with different protein sources cause increases in urinary excretion of plasma proteins in healthy subjects, urinary excretions of various plasma proteins with various molecular radii and isoelectric points, namely albumin (Alb), IgG, IgG4, ceruloplasmin (CRL), and α2-macroglobulin (A2), were measured in healthy subjects after ingestion of a beef meal or of a tuna fish meal. Significant increases in urinary excretions of the negatively charged IgG4 and CRL and of the neutrally charged IgG were found in parallel with enhanced creatinine clearances after each protein ingestion. These renal responses returned to basal levels 9 h after the test. This finding suggests that in healthy subjects, the increase in glomerular filtration rate after acute protein loading caused selective enhancement of urinary excretions of plasma proteins with a molecular radius of approximately 55 Å (the radius of IgG, IgG4, and CRL), irrespective of the charge barrier of the glomerulus. The increases in these three plasma proteins may be induced by leakage via the shunt pathway in the glomerulus, as proposed earlier (see text). In contrast, increases in urinary excretions of A2 and Alb were not found. The former finding may be explained by the possibility that A2 would not pass through this pathway, since the molecular radius of A2 (88 Å) is larger than that of IgG, although the latter finding may be partially explained by preferential renal tubular reabsorption of Alb.