Demonstration of opsonizing antibodies to Francisella tularensis by leukocyte chemiluminescence

Abstract

Individuals (23) were vaccinated with a viable attenuated strain of F. tularensis, and blood was collected at various time intervals during 4 wk. To demonstrate opsonizing antibodies, a mixture of serum and vaccine bacteria was incubated, whereafter the chemiluminescent response of polymorphonuclear (PMN) leukocytes to this mixture was recorded. No opsonizing antibodies against F. tularensis were found in sera obtained before vaccination. Eleven days after vaccination, sera from 9 individuals, and 21 days after vaccination, sera from all 23 individuals contained antibodies. Antibodies were demonstrated earlier with the chemiluminescent technique than with the agglutination reaction. Heat treatment (56.degree. C, 30 min) or removal of complement component C3 from immune serum reduced the chemiluminescent response of the leukocytes. A high chemiluminescent response of the leukocytes was induced by immunoglobulin IgG and IgM-enriched fractions of immune serum in the presence of complement. In the absence of complement, the IgG fraction induced a low chemiluminescent response; the IgM fraction induced no response at all.