Studies on Pasteurella multocida. III. In vitro assay for cell-mediated immunity.

Peripheral blood lymphocytes (PBL) from turkeys immunized against fowl cholera with a bacterin or a live avirulent vaccine (strain CS-148) were cultured in vitro with various antigenic preparations from Pasteurella multocida (strain P-1059). The degree of lymphocyte stimulation (blastogenesis) was quantitated by measurement of the uptake of (3H) thymidine. Higher stimulation indices were obtained with immune lymphocytes rather than nonimmune lymphocytes. Stimulation was specific since PBL from turkeys immunized against P. multocida failed to react with Escherichia coli or Mycoplasma synoviae antigens. These differences were statistically significant as analyzed with the student's t-test. The lymphocyte transformation assay was emphasized as a convenient and useful in vitro indicator of cell-mediated immunity that should help define the role of cell-mediated immunity in P. multocida infections of turkeys.