S100A8 and vitamin B12 deficiency: Typical diseases chiefly rely on this mechanism, including cross reaction between CagA antibody and vascular wall inducing atherosclerosis; H. pylori and gastric H+K+ATPase cross antigen contributes to vitamin B12 deficiency; arteriosclerosis of fundus for autoimmune reaction induces central serous choroidal retinopathy (CSR); and cross-antigen reactivity between spermatogenesis related proteins, sperm motility related proteins and H. pylori contributes to hypomotility of sperm (Figure 4).