The Protective Effects of Helicobacter pylori Infection on Allergic Asthma

Abstract

As an ancient Gram-negative bacterium, <i>Helicobacter pylori</i> has settled in human stomach. Eradicating <i>H. pylori</i> increases the morbidities of asthma and other allergic diseases. Therefore, <i>H. pylori</i> might play a protective role against asthma. The “disappearing microbiota” hypothesis suggests that the absence of certain types of the ancestral microbiota could change the development of immunology, metabolism, and cognitive ability in our early life, contributing to the development of some diseases. And the Hygiene Hypothesis links early environmental and microbial exposure to the prevalence of atopic allergies and asthma. Exposure to the environment and microbes can influence the growing immune system and protect subsequent immune-mediated diseases. <i>H. pylori</i> can inhibit allergic asthma by regulating the ratio of helper T cells 1/2 (Th1/Th2), Th17/regulatory T cells (Tregs), etc. <i>H. pylori</i> can also target dendritic cells to promote immune tolerance and enhance the protective effect on allergic asthma, and this effect relies on highly suppressed Tregs. The remote regulation of lung immune function by <i>H. pylori</i> is consistent with the gut-lung axis theory. Perhaps, <i>H. pylori</i> also protects against asthma by altering levels of stomach hormones, affecting the autonomic nervous system and lowering the expression of heat shock protein 70. Therapeutic products from <i>H. pylori</i> may be used to prevent and treat asthma. This paper reviews the possible protective influence of <i>H. pylori</i> on allergic asthma and the possible application of <i>H. pylori</i> in treating asthma.