STAT1 and infection: However, in cells expressing misfolding forms of HLA-B27 (the B27g and B27H9F transfectants), the phosphorylation of STAT-1 serine 727 persisted high even at later time points (5 h and 8 h) and close to the level observed at 15 minutes time point, while in the mock and B27E45M-transfected cells the phosphorylation of STAT-1 serine 727 was transient and decreased near the level observed before infection (time point C) in time (Figure 1).