Influence of Escherichia coli lipopolysaccharide on histamine-forming capacity and antibody formation in lymphoid tissues.

Mice were injected intraperitoneally with 50 mug of Escherichia coli lipopolysaccharide (LPS). The spleen tissue exhibited increased histamine-forming capacity (HFC) 4 hr later. When this increased HFC was produced within 12 hr after intraperitoneal injection of sheep red blood cells (SRBC), there was an enhanced anti-SRBC antibody response in the spleen. In mice experiencing an increased spleen HFC at 36 hr after injection of SRBC, there was a significant decrease in the number of antibody-producing cells. The injection of histidine decarboxylase inhibitors simultaneously with the LPS greatly reduced the stimulation of HFC and also the adjuvant activity of the LPS.