Interaction ofMycoplasma dispar withBovine Alveolar Macrophages

Thecapacity toavoidphagocytosis andtheactivation ofbovinealveolar macrophages (BAM)by encapsulated Mycoplasma dispar or purified M.dispar capsule was investigated. Encapsulated andunencapsulated M. dispar were cocultured withBAM inthepresenceor absenceofantisera prepared against unencapsulated M.dispar or purified capsule antiserum. Unopsonized mycoplasmas resisted phagocytosis, whileonlyanti-capsule antibodies enhanced thephagocytosis ofencapsulated mycoplasmas. BAM were cultured inthepresenceofpurified M. dispar capsule or either liveor heat-killed encapsulated or unencapsulated M.dispar. TheseBAM were thenactivated withEscherichia coliendotoxin or left without further activation. Thesupernatants ofthese cultures were assayed fortumornecrosis factor, interleukin 1, andglucose consumption asindicators ofmacrophage activation. Tumornecrosis factor andinterleukin 1were produced byBAM stimulated withunencapsulated M.dispar butnotwhenencapsulated M. dispar or its purified capsule was used.Similarly, glucose consumption was increased inthepresenceofunencapsulated M. dispar, butnotwhenBAM werecocultured withencapsulated M.dispar orpurified capsule. WhenBAM were treated withpurified capsule or encapsulated mycoplasmas, theycouldnotbesubsequently activated by endotoxin. Theseresults indicate thatencapsulated M.dispar orpurified capsule exerts an inhibitory effect on theactivity ofBAM andprevents theactivation ofthese cells. Alveolar macrophages arecentral intheprotection ofthe lowerportions ofthelungs, operating inmany nonspecific modesofdefense andaugmented byspecific immunologic mechanisms. Previous studies haveshownthatalveolar macrophages ingest, inactivate, anddegrade inhaled microorganisms within 8hoftheir entrance intoalveolar regions (11). Suchantimicrobial ability ofmacrophages iscentered on their phagocytic capabilities andintheproduction of potentmicrobicidal anddegradative substances within the macrophage.