Immune responses to influenza virus in rabbits after local immunization. II. Local and systemic cell mediated response.

The development of local and systemic cell mediated immunity (CMI) was investigated in rabbits after intratracheal immunization with live or inactivated influenza A virus. Lymphocytes from bronchoalveolar washings and draining lymph nodes were used for the assay of local CMI response. Spleen cells were employed for determination of systemic responses. Since alveolar macrophages were found to be susceptible to the action of migration inhibiting factor, the development of CMI in lungs was assayed by macrophage migration inhibition test using bronchoalveolar was cells. Immunization with live virus induces beter local CMI response than inactivated virus. After primary immunization the peak responses were found between second and third week. The secondary response was detectable much earlier and peaked at one week after booster. Small amounts of inactivates virus, which was unsufficient to evoke a primary response, could elicit a strong secondary response. The development of rapid and accentuated secondary response in the local lymphoid tissues suggests the presence of memory in the local CMI response. The results also show a good correlation to exist between primary local CMI response and the skin reactivity to the immunizing antigen. However, lack of such correlation during the secondary response leaves the skin tests less reliable in the evaluation of CMI in viral infections. Some of the functions of alveolar macrophages in the local immune reponses are also discussed.