ICOS and systemic lupus erythematosus: Similar to what was observed in the SRBC-immunized BALB/c mice, blocking ICOS signaling led to a significant decrease in number of both GC B cells (∼65% reduction, p<0.01) and Tfh (CD4+ CD44high CXCR5+Bcl6+) cells (∼70% reduction, p<0.01) in this spontaneous autoimmune model of lupus (Figure 7 B and D).