Strong associations of H. pylori with some autoimmune diseases such as immune thrombocytopenia have been found; but most other autoimmune disease studies have revealed conflicting data. The chronic survival of H. pylori in humans is possible because of an overall downregulation of the body's immune response. In addition to this overall effect on the immune system, there are clinical and epidemiological data suggestive of H. pylori infection having a protective role in some autoimmune diseases.
Martin J. Blaser describes in the article that I attach, in addition to the canonical correlations between HP and pathology, this different way of looking at this subject: "Absence of an immunologic response to H. pylori: an important contributor to atopic and allergic disorders? The hygiene hypothesis "
Coadaptation of Helicobacter pylori and humans: ancient history, modern implications
I want to add that there are reports on mice and humans, where H. pylori infection causes the generation of ectopic Germinal Centers which can contribute to the generation of pathogenic autoantibodies. However, additional genetic predisposition would be necessary for an autoimmune phenotype development.