Immunoglobulin Class-Specific Antibody Response in Serum, Spleen, Lungs, and Bronchoalveolar Washings After Primary and Secondary Sendai Virus Infection of Germfree Mice

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Abstract
Immunoglobulin class-specific antibodies were measured by a solid-phase radioimmunoassay in serum, bronchoalveolar washings (BAW), lung cell lysates, and spleen cell lysates in germfree mice after intranasal (i.n.) and intraperitoneal (i.p.) primary and secondary 10 5 , 10 4 , and 10 3 mean tissue culture infective doses (TCID 50 ) of live parainfluenza 1 (Sendai) virus. The earliest antibody detected in lungs after i.n. virus challenge was immunoglobulin G (IgG), followed by IgM and, lastly, IgA. The local IgA response after both primary and secondary i.n. virus challenge was lowest after the severest infection. It is suggested that the delayed appearance of IgA antibody and the lower response after severe lung damage may be related to a temporary local secretory component-producing cell deficiency. The lungs were a major source of serum IgG antibody after both primary and secondary i.n. virus challenge. Only IgG and IgM antibodies were detectable in lung cell lysates after the i.n. 10 3 TCID 50 secondary response. A secondary response was detected in IgG, IgA, and IgM after secondary i.n. challenge with the other two doses. The lung response to all of primary and secondary i.p. doses of virus was exclusively IgG and IgM. Calculation of radioimmunoassay antibody per microgram of IgG, IgA, and IgM in serum and BAW after both i.n. and i.p. virus challenges showed that, when BAW antibody was present, the ratio in BAW was always higher than that in serum. This finding in the i.n. mice, together with the presence of IgA antibody-containing cells in the lungs, strongly indicates local manufacture and secretion of IgA antibodies in these animals and suggests that the same conclusion could apply to local IgG and IgM antibodies after both i.n. and i.p. challenges.