Gastritis, or inflammation of the stomach lining, can be acute or chronic. Histologically, acute gastritis is characterized by the infiltration of neutrophils into the superficial layers of the gastric mucosa. Chronic gastritis, on the other hand, involves the presence of lymphocytes and plasma cells in the deeper layers. Additionally, there may be a loss of the normal gastric gland architecture and the presence of intestinal metaplasia, where the gastric epithelium transforms into an intestinal-type epithelium.