Lymphotoxin-alpha-deficient mice can clear a productive infection with murine gammaherpesvirus 68 but fail to develop splenomegaly or lymphocytosis

Respiratory challenge with murine gammaherpesvirus 68 (MHV-68) leads to an acute productive infection of the lung and a persistent latent infection in B lymphocytes, epithelia, and macrophages. The virus also induces splenome galy and an increase in the number of activated CD8 T cells in the circulat ion. Lymphotoxin-alpha-deficient (LT alpha(-/-)) mice have no lymph nodes a nd have disrupted splenic architecture. Surprisingly, in spite of the sever e defect in secondary lymphoid tissue, LT alpha(-/-) mice could clear a pro ductive MHV-68 infection, although with delayed kinetics compared to wild-t ype mice, and could control latent infection. Cytotoxic T-cell activity was comparable in the lungs and spleens of LT alpha(-/-) and wild-type mice. H owever, splenic gamma interferon responses were substantially reduced in LT alpha(-/-) mice. Furthermore, LT alpha(-/-) mice failed to develop splenom egaly or lymphocytosis. Although germinal centers were absent, LT alpha(-/- ) mice were able to class switch and showed significant virus-specific anti body titers. This work demonstrates that organized secondary lymphoid tissu e is not an absolute requirement for the generation of immune responses to viral infections.