CD28 and hip fracture: Finally, on examining frequency of CD28-veCD57+ve CD4 T cells significant differences, F (2, 56) = 6.28, p = .003, η2 = .18 occurred [Additional file 1: Figure S1a], due to increased frequency of CD28-ve CD57+ve CD4 T cells in hip fracture patients with depressive symptoms compared with healthy controls, p = .002, but not on comparison with hip fracture patients without depressive symptoms, p = .13.