Study Background: Toxoplasma gondii a protozoan and zoonotic infection can stimulate innate and adaptive immune responses. Aims
and Objectives: This work was designed to determine relationship between parasitic infection of T. gondii, interleukin?2 (IL?2), tumor
necrosis factor?alpha (TNF??), and Tryptophan and CD4+ count. Materials and Methods: A total of 150 individuals aged 21–73 years
(male: 100 and female: 50) were recruited from Saki?West, Saki?East, and ATISBO local governments of Nigeria. Plasma TNF??, IL?2,
Tryptophan, anti?hepatitis C virus (anti?HCV), hepatitis B surface antigen (HBsAg), anti?HIV, Plasmodium, and T. gondii infections
were determined in each of the subjects. The results were used to group the subjects into: Control (n = 104; individuals not infected with
T. gondii noninfected, Plasmodium spp., HIV or HCV); T. gondii mono?infected patients (n = 9) and patients with T. gondii co?infection
with Plasmodium spp., HIV, HBV, or HCV. Plasma TNF??, IL?2, anti?HCV, HBsAg, and anti?HIV were determined by enzyme?Linked
Immunosorbent Assay. Plasmodium spp., was identified by thick blood film?Giemsa staining technique. Plasma tryptophan was determined
by fluorometry. Results: Of 150 subjects recruited for the work, the results obtained showed a frequency of occurrence of 69.3% (104) T.
gondii noninfected control not infected with Plasmodium spp., HIV, HBV, and HCV; 8.0% (9) T. gondii?infected patients not infected with
Plasmodium spp., HIV and HCV; 22% (33) were infected with at least one of the Plasmodium spp., HIV, HBV, and HCV; 2.7% (4) T. gondii
patients co?infected with at least one of the Plasmodium spp., HIV, HBV, and HCV. There was a significant decrease in plasma tryptophan
in T. gondii mono? and co?infection including T. gondii noninfected individuals but infected with at least Plasmodium spp., HIV, HBV,
and HCV compared with the control [P < 0.05]. There was a significant decrease in CD4 count in T. gondii noninfected individuals but
infected with at least one of the Plasmodium spp., HIV, HBV, and HCV and T. gondii co?infection compared with T. gondii mono?infection;
controls and also in T. gondii noninfected individuals but infected with at least one of the Plasmodium spp., HIV, HBV, and HCV compared
to T. gondii confection (P < 0.05). There was a significant increase in plasma TNF?? in T. gondii mono?infected patients compared with
the controls; T. gondii noninfected individuals but infected with at least one of the Plasmodium spp., HIV, HBV, and HCV compared to
controls; T. gondii confection compared to controls; T. gondii mono?infected patients compared to T. gondii noninfected individuals but
infected with at least one of the Plasmodium spp., HIV, HBV, and HCV; T. gondii mono?infected patients compared to T. gondii co?infection
and T. gondii noninfected individuals but infected with at least one of the Plasmodium spp., HIV, HBV, and HCV compared to T. gondii
confection (P < 0.05). Conclusion: T. gondii and its coinfection with HIV, HCV, and HBV caused a significant immunological alterations
in the plasma values of IL?2, TNF??, Tryptophan, and blood CD4+ count.