Cellular aspects of local antibody response in rabbits

Live or inactivated influenza virus is inoculated intratracheally to rabbit. After 4 days or more, lungs are washed with 50 ml of saline and fluid is examined for immunoglobulin and antibody content as well as for type and properties of free cells. IgA and IgG are detectable in the fluid but not IgM. Specific antiviral activity is associated only with IgA at the earliest stages. Free cells are so called 'alveolar macrophages' as demonstrated by shape and phagocytic or enzymatic properties. Their total numbers vary according to type of immunization: non-immunized 5.10-5. inactivated virus 2.10-6. live virus 10.10-6. A high percentage (50 to 90 percent) are positive in IgA IF test, only 10 percent with IgG test. Peroxydase electron microscopy shows intracellular presence of IgA.