Relationship between the production of interferon-alpha/beta and interferon-gamma during acute toxoplasmosis.

Acute toxoplasmosis was induced in mice, and interferon (IFN) production in serum and by spleen cells was evaluated during the infection period. Interferon was characterized by acid-treatment and anti-IFN-alpha/beta neutralization. In order to verify the correlation between the unusual aspects of the IFN production and the induction of immunosuppression, splenocyte mitogen responsiveness was investigated concomitantly to IFN synthesis. The activity of Toxoplasma-induced serum IFN-alpha/beta increased gradually throughout all post-infection days, but IFN-gamma was not detected in the systemic circulation at any time during the infection. It was also observed that IFN-alpha/beta production and the capacity to produce IFN-gamma by spleen cells were closely and inversely correlated. As the infection progressed, more IFN-alpha/beta was produced, and the ability of spleen cells to produce IFN-gamma decreased. The observation that Toxoplasma-infected mice were concomitantly immunosuppressed (as documented by mitogen unresponsiveness and defective IFN-gamma production) in direct correlation to IFN-alpha/beta production, suggests that such IFN-alpha/beta production is an important factor associated with acute toxoplasmosis-induced immunosuppression.