CD28 and cardioembolic stroke: Subjects with cardioembolic stroke showed a significantly higher peripheral frequency of CD4+ cells compared to subjects with LAAS and lacunar subtype (51.7 ± 6.1% vs 45.3 ± 6.9% vs 43.6 ± 7.5%; P = 0.012) and of CD28 null cells compared to subjects with LAAS and lacunar subtypes (7.5 ± 2.0% vs 5.4 ± 1.8% vs 3.7 ± 1.5%; P = 0.0001).