Figure 1.

Hypothetical model how CD44 and CD44v contribute to the CLL cell life cycle. By the ability of CD44 to complex with VLA-4 (CD49d/CD29), a key molecule for homing of CLL cells, CD44 may influence the homing process. Interstitial migration in the lymphoid organs is CD44 independent but mediated by RHAMM binding to hyaluronan. Interactions with T-cells and hyaluronan-displaying stromal cells secure CLL cell survival and activate the malignant cells. Activation is responsible for a rearrangement from CD44s to CD44v expression enhancing the affinity for hyaluronan, which induces a stop signal for the CLL cell. This retention allows CLL cell proliferation.