BTLA and B-cell chronic lymphocytic leukemia: For a subset of stimulated BTLA+ T cells coexpressing sCTLA-4 or cCTLA-4 molecules, the median proportions of those cells were similar in both groups due to an increase in sCTLA-4 abundance in the controls (p = 0.079) and a decrease in cCTLA-4 in the CLL patients (p = 0.006; Figure 5).