CD28 and hip fracture: On examining the frequency of circulating CD28-ve CD4 T cells, we found significant differences between the three groups, F (2, 62) = 5.26, p = .008, η2 = .14, driven by a significant increase in the percentage of CD28-ve CD4 T cells in hip fracture patients with depressive symptoms compared with healthy controls (p = .01) and hip fracture patients without depressive symptoms (p = .04) [Figure 2b].