JAKi treatment in our mouse model of ICI-T1DM led to significantly fewer effector CD44+CD4+ T cells (Figure 4A; P < 0.05) and Tfh cells (ICOS+PD-1hiCXCR5+) within pancreatic islets (Figure 4B; P < 0.01). Here, ICOS is linked to type 1 diabetes mellitus.