CHARACTERISTICS OF THE IMMUNOLOGICAL RESPONSE IN THE CLEARANCE OF NONTYPABLE HAEMOPHILUS-INFLUENZAE FROM THE LUNG

Clearance of non-typeable Haemophilus influenzae (NTHi) from the respi ratory tract was investigated, over time, in immune and non-immune rat s. A triphasic pattern characterized the clearance of bacteria from th e lungs. Mucosal immunization enhanced bacterial clearance from the lu ngs in each of the three phases compared with clearance from non-immun ized animals. Total clearance of bacteria was observed from lung tissu e by 12 h in immune animals and 24 h in non-immune animals. Polymorpho nuclear leucocytes not only arrived earlier and initially in greater n umbers, but disappeared earlier in immune animals (peaking at 8 h post challenge), compared with non-immune animals (peaking at 12 h post-cha llenge). Systemically derived and locally produced NTHi-specific IgA a nd IgG correlated with enhanced bacterial clearance during the seconda ry phase. This model demonstrates that immunized animals up-regulate a nd resolve inflammatory responses to pulmonary infection more rapidly than the non-immunized controls.