Litomosoides sigmodontis is parasitic filarial nematode that can infect mice, and is used as a murine model for human filariasis. Type 2 immune responses are protective, but infection is typically chronic due to a combination of immune suppression by the parasite and immune regulation by the host dampening protective Type 2 immunity.
We have shown that the CD4+ Th2 cells develop an intrinsically hyporesponsive or dysfunctional phenotype between day 20 and 60 of infection, denoted by an impaired ability to proliferate and produce Th2 cytokines. The hyporesponsive phenotype is PD-1/PD-L2 dependent, and impairs parasite killing (van der Werf et al. 2013. PloS Path. e1003215). This study aimed to investigate the mRNA expression of the intrinsically-hyporesponsive Th2 cells to determine the mechanisms by which they become dysfunctional, and to test whether Th2 cell intrinsic hyporesponsiveness has similarities with other forms of T cell-intrinsic regulation such as exhaustion, tolerance or anergy.
The study included 6 groups with 4 – 5 biological replicates per group. For four of the groups, BALB/c IL-4gfp 4get reporter mice were infected with L. sigmodontis. CD4+IL-4gfp+ Th2 cells were purified from the infection site (pleural cavity, PleC), and CD4+IL-4gfp+CXCR5- Th2 cells purified from the lymph nodes within the thoracic cavity (tLN). Th2 cells were sampled pre-onset of hyporesponsiveness (day 20 post-infection) and post-onset of hyporesponsiveness (day 60 post-infection). To generate a reference Th2 population, CD4+IL-4gfp+CXCR5- were purified from the tLN of mice infected with the parasitic nematode Nippostrongylus brasiliensis for 6 days. N. brasiliensis stimulates a prototypical acute Th2 response, and the tLN drain its lung migration stage. Naïve CD4+IL-4gfp-CXCR5-CD25-CD44-CD62L+CD45RB+ T cells were purified from the spleens of uninfected mice as a control. Due to limiting cell numbers, each biological replicate was created by pooling cells from 20 – 31 mice for day 20 L. sigmodontis infection, 16 – 21 mice for day 60 L. sigmodontis infection, 20 – 23 for N. brasiliensis infection, and 3 naïve mice.