3.1. Assessment of Parasitemia
The assessment of parasitemia curve shows first days of analysis, that they were similar for the control (CI) and ethanol-pre-exposed infected (EtOH-I) groups (Figure 1). However, animals in this group (EtOH-I), presented a higher parasite counting (trypomastigotes) in the blood from the beginning of the patent period-PP (the seventh day after infection), until the eighth day post-infection, when compared to the control infected group (p<0.05). Interestingly, around the seventh-day post-infection, an increase in the number of circulating parasites was observed in both groups, with the level of parasitemia remaining higher in the ethanol-pre-exposed T. cruzi -infected mice (ETOH-I) than in the control group until the seventh day (p<0.05). On the ninth day, there was a peak of parasitemia for both groups, and no difference in the level of parasitemia was observed until the end of the experiment. Both groups presented the same dynamics of parasitemia control, at least regarding the decrease of circulating parasites.
3.2. CD8+ T Lymphocytes Dominate IL-4 Production in Unstimulated Immune Cells, While Innate Immunity Exhibits Reduced Cytokine Production in T. cruzi-Infected Mice Pre-Exposed to Ethanol
The production of IL-4, IL-10, and IFN-γ was evaluated in unstimulated splenic CD4⁺ T lymphocytes, with no differences observed among groups (Figure 2A). However, CD8⁺ T lymphocytes from ethanol-pre-exposed andT. cruzi- infected mice (EtOH-I) showed increased IL-4 levels compared to all other groups (Figure 2B). Regarding IL-10, CD8⁺ T cells from control-infected mice (CI) produced more of this cytokine, indicating a modulatory response to infection, while EtOH-I CD8⁺ T cells exhibited elevated IFN-γ compared to non-infected controls (NI). For B lymphocytes, T. cruzi infection led to reduced IL-10 production in both infected groups (CI and EtOH-I), regardless of ethanol exposure (Figure 2C).
Innate immunity showed a distinct pattern. Ethanol-pre-exposed uninfected mice displayed higher IL-10 and IFN-γ levels in NK cells, while only IFN-γ was elevated in the EtOH-I group. For monocytes and dendritic cells, IL-10 and TNF-α production was assessed (Figure 3A). Macrophages from ethanol-pre-exposed uninfected mice exhibited increased IL-10 and TNF-α, whereas EtOH-I mice showed a significant reduction (Figure 3B). No differences were detected in cytokine production by dendritic cells among groups (Figure 3C).