Granulocyte infiltration was studied in 88 biopsies of antrum mucosa from patients with B-gastritis. Evidence of IgA-, IgG- and IgM-antibodies as well as of lysozyme in the mucosa was demonstrated by immunohistochemical methods. Helicobacter pylori (Hp) is coated by antibodies and a significant correlation between extent of opsonisation and number of plasma cells in the connective tissue of the lamina propria could be stated. Thus, the infiltration of plasma cells is a specific immune response against Hp. In the depths of gastric pits the antibody-coating of bacteria is faint. Instead, lysozyme and lactoferrin are produced there. By means of a Cross-sectional study a model is developed which characterizes B-gastritis as a dynamic process. Lagging behind, the inflammation follows the motile bacteria resulting in a patchy distribution of inflamed areas in the mucosa. At the peak of these local inflammation-waves the production of antibodies and lysozyme is intensified. Coating the bacteria with IgG and IgM results in complement activation liberating chemotaxin C5a. Consequently, there is a massive granulocyte infiltration leading to local reduction or eradication of Hp.