Toxoplasma Gondii Is a Single-Celled Parasitic Protozoan That Infects and Replicates

Multiple Choice

Toxoplasma gondii is a single-celled parasitic protozoan that infects and replicates in macrophages. It is common in the environment, and is transmitted to humans by the ingestion of undercooked meat or by accidental ingestion of the parasite's oocytes from contaminated water or cat litter. Infected individuals with healthy immune systems are generally asymptomatic, and rapidly clear the infection. However, in AIDS patients, infections of Toxoplasma gondii can lead to severe disease and even death. To investigate the immune mechanisms important in controlling Toxoplasma gondii, a mouse model of the infection was developed. Mice were infected with the protozoa at a dose where the majority of the mice survive the infection, and at the same time, were injected with a neutralizing antibody to a cytokine made by T cells (anti-'X' IgG) . A second group of mice received the protozoa plus a control IgG antibody, as shown in Figure Q10) . Figure Q10) The most likely candidate for cytokine 'X' is:

A) IFN- $\gamma$
B) IL-2
C) IL-4
D) IL-17
E) GM-CSF