ABSTRACT
Bacteria of the genus Rickettsia are obligate intracellular microorganisms which grow directly in the cytoplasm of their host cells, unbounded by a phagosomal or phagolysosomal membrane. When the cells are treated with lymphokines before infection only, inhibition of rickettsial growth is much less pronounced, and the antirickettsial effect of the lymphokines is greater during the interval from 0 to 24 hr after infection than during the interval from 24 to 48 hr after infection. Because interferons also require host cell protein synthesis for activity and manifest species preference in exerting their effects on cells, these features of lymphokine-mediated induction of antirickettsial activity suggest the participation of IFN. In addition, lymphokine-induced suppression of the initial rickettsial infection in L929 cells is partially inhibited by adding cycloheximide to the cells at the same time that the lymphokines are added, and suppression of the initial rickettsial infection occur in mouse lymphokine-treated human fibroblasts.
