CD4 and B-cell chronic lymphocytic leukemia: To this end, we confirmed that LN samples contained significantly more T cells compared with PB samples, which was specifically due to the increased number of CD4+ T cells in the LN (Figure 1A and 1B).10 For this reason, we selected PB samples from our CLL biobank containing >10% CD4+ T cells to mimic CD4+CD40L+ T cell help in the LN using primary PBMCs.