Lymphocyte subsets in bronchoalveolar lavage after exposure to Actinobacillus pleuropneumoniae in pigs previously immunized orally or by aerosol

Abstract

Young pigs were immunized with the lung-pathogenic bacterium Actinobacillus (Haemophilus) pleuropneumoniae by aerosol or orally using viable and inactivated bacteria. The cellular changes in the bronchoalveolar lavage (BAL) were studied in repeated lavages after the pigs were infected with live bacteria. The nucleated cells in the BAL were differentiated and lymphocyte subsets determined. There were no major differences between the two routes of immunization or between viable and inactivated bacteria. The immunization induced an increase in all lymphocyte subsets studied and in the appearance of plasma cells and lymphoid blasts. The infection did not cause a further increase except in granulocytes. The lack of a booster-type increase in lymphocytes in the BAL might indicate a different immunologic reaction of the lung or that lymphocytes of the BAL do not represent lung lymphocytes in general. The protective effect of the immunization might be deduced from the increase in lymphocytes after immunization but not from the reaction pattern after infection.

Bronchoalveolar Lavage Cytology and Hematology: A Comparison between High and Low Health Status Pigs at Three Different Ages

“…This is in agreement with findings by others. 4,18,24 A third BAL was done at necropsy after removing the lung from the chest cavity. The BALs were done at 2.5-week intervals, which would allow enough time for resolution of any mild inflammatory response.…”

Evidence for a common mucosal immune system in the pig

“…There was a significant increase in IgA+ ASCs in BALs after immunization with inactivated bacteria but there was a significant increase in IgG+ and IgM+ ASCs in pigs orally immunized with viable or nonviable bacteria. Thus, oral administration of either viable or inactivated A. pleuropneumoniae induced an influx of lymphocytes into the bronchoalveolar compartment of pigs, indicating a migration from the gut or lamina propria of the bronchi and trachea into the airways (Delventhal et al, 1992;Pabst et al, 1995).…”

“…Relative to the animals orally immunized with inactivated bacteria, the pigs immunized with viable bacteria showed a trend toward higher numbers of nucleated cells and an increased proportion of granulocytes, a comparable 40% composition of macrophages, and a constant proportion of about 2-5% lymphoid blasts and plasma cells were found. In the BAL of normal pigs, plasma cells and blasts are rare but the percentage of plasma cells in BAL increased significantly after oral immunization with either viable or non-viable bacteria (Delventhal et al, 1992;Pabst et al, 1995). Immunization with either viable or noviable bacteria triggered an overall increase in the total number of T cells but the ratio of CD4/CD8 cells remained constant.…”

“…Oral immunization with the Actinobacillus pleuropneumoniae (live or killed) and the impact on lymphocyte subset distribution in the bronchoalveolar space and ASCs in lavage fluid and sera (Delventhal et al, 1992;Pabst et al, 1995) In these experiments, four month old German Landrace pigs from an SPF breeding farm were used (Delventhal et al, 1992;Pabst et al, 1995). A 'lavage' control group (n = 5) were lavaged at week one, five and six (without being immunized) (Delventhal et al, 1992;Pabst et al, 1995). Another 'non-immunization' control group was lavaged then infected by aerosol challenge and lavaged again one week later.…”

“…Another 'non-immunization' control group was lavaged then infected by aerosol challenge and lavaged again one week later. The experimental pigs were lavaged followed by orally immunized with 10 11 active or inactive (irradiated) bacteria (Delventhal et al, 1992;Pabst et al, 1995). All groups (with the exception of the lavage control group) were infected by aerosol challenge with 10 8 viable APP at week five then lavaged one week later.…”