Lansoprazole increases serum IgG and IgM in H. pylori-infected patients

Proton-pump inhibitors have been reported to influence the human immune system, we therefore evaluated the effect of lansoprazole, a proton-pump inhibitor, on humoral immunity. Patients with gastric ulcer received lansoprazole 30 mg/day for 8 weeks, and serum immunoglobulins were evaluated before and upon completion of the treatment. There were 79 patients with gastric ulcer; 51 were H. pylori-infected and 28 were H. pylori-uninfected. Eighteen patients positive for H. pylori were receiving at least one non-steroidal anti-inflammatory drug, and 12 patients negative for H. pylori received one non-steroidal anti-inflammatory drug. H. pylori-infected patients showed significant increases in serum immunoglobulins G and M 8 weeks after the start of lansoprazole treatment (P<0.001 for IgG and P<0.01 for IgM), but uninfected patients did not. Even when H. pylori-infected patients receiving a non-steroidal anti-inflammatory drug or low-dose aspirin were analyzed separately, these increases were seen (P<0.001 for IgG and P<0.005 for IgM). Lansoprazole elevated serum levels of immunoglobulins G and M in gastric ulcer patients with H. pylori infection, particularly in those receiving non-steroidal anti-inflammatory drugs. Deducing from these observations, lansoprazole might alter the Th1 shift in the immune response induced by H. pylori infection.