Effect of extracts of Hemophilus pertussis on leukocyte counts in normal and sensitized mice

Mice, sensitized by intranasal infection with sublethal doses of H. pertussis, were injected intra-abdominally 3 weeks later with extracts of the organism in order to observe their leukocytic response compared with that of normal mice. After injection of an extract prepared by sonic disruption of the organism, a significantly greater increase of the total leukocyte count, particularly of the polymorphonuclear cells occurred in the sensitized animals. A similar, though somewhat lesser, response followed injection of this extract previously freed of agglutinogen by absorption with a specific antibacterial rabbit serum. No significant increase occurred after injection of the extract after heating, after heating and absorption, or after injection of physiological salt solution. Under the conditions of the experiments leukocytosis, chiefly caused by an increase of the polymorphonuclear cells, appeared to be associated with the heat-labile component of the extracts tested.