NEUTROPHILS ACTIVATED BY IMMUNOCOMPLEXES MODULATE CD4 T CELL RESPONSE IN LYMPH NODES

SOFÍA DAIANA CASTELL, MARÍA FLORENCIA, GABRIEL MORÓN, BELKYS MALETTO, MARÍA CRISTINA PISTORESI

Congreso; Reunión Conjunta Sociedades de Biociencias; 2017

Previously we demonstrated that immunocomplexes (IC) generated by injecting OVA in the footpad of immunized mice that have anti-OVA antibodies, induce the migration of OVA+ neutrophil to draining popliteal lymph nodes (D-poLNs). In the present study we evaluate the influence of neutrophils activated by IC on CD4 T cell response in lymph nodes. C57BL/6 mice were immunized with OVA emulsified in Freund?s complete adjuvant and 15 days later boosted with OVA emulsified in Freund?s incomplete adjuvant. Ten days after last immunization they were injected with OVA-FITC in the footpad and D-poLNs were obtained 6 to 48 h later; saline solution was injected on footpad corresponding to control non-draining popliteal lymph nodes (ND-poLNs). OVA+ neutrophils migrated to D-poLNs 6 h after OVA injection (p<0.001) and at 12 h they were no longer detected. At longer times, we observed that total number of D-poLNs cells increase (p<0.01). Particularly, a greater number of CD4 T cells were detected at 48 h in D-poLNs compared to ND-poLNs (p<0.001). Naïve (p<0.05), effector memory (p<0.01) and central memory (p<0.001) subtypes were increased. Interesting, CD4 T cells exhibited higher expression of CD69 (p<0.001) and Ki67 (p<0.001) and higher production of IFNg (p<0.05) and IL17 (p<0.05) when compared to CD4 T cells in ND-poLNs. Moreover, D-poLNs showed an increase in Foxp3+CD25+ Treg population (p<0.001). In order to confirm the influence of neutrophils in CD4 T cells response, we treated mice with anti-Ly6G to deplete neutrophils. We observed a lower number of total poLNs cells (p<0.001), CD4 T cells (p<0.01) and Treg cells (p<0.01) in D-poLNs from mice depleted of neutrophils compare to D-poLNs from isotype treated mice. Besides, CD4 T cells and Tregs showed lower levels of Ki67 (p<0.05) when mice were treated with anti-Ly6G. These findings indicate that OVA+ neutrophils in D-poLNs promote CD4 T cells proliferation and activation, as well as the development of Tregs.