ICOS and arthritic joint disease: In this sense, we observed a higher proportion of CXCR5+ T cells in the lymph nodes of p110α−/−ΔT in the pre-arthritis stage (Figure 8) and an increased expression of the surface markers ICOS, CXCR5 and CD44 in T-cell blasts of p110α−/−ΔT mice (Figure 7).