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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Trends Immunol. 2013 Aug 5;34(12):592–601. doi: 10.1016/j.it.2013.07.002

Figure 2. Mechanism of BCR activation in CLL.

Figure 2

(A) BCR signaling can be activated in an exo-antigen-independent fashion, for example by interactions between the third complementary determining region of the IG heavy chain variable domain (HCDR3) with an epitope in the second framework region (FR2) of either the same smIg or an adjacent smIg. The latter would lead to calcium signaling[15]. (B) Exo-antigen-dependent activation of the BCR in CLL can occur in an antigen-restricted, specific and high-affinity fashion in M-CLL, or in a less restricted, low-affinity fashion (U-CLL). Examples of CLL BCR ligands are given next to each of the red stars, which represent the BCR ligand. BCR signaling in U-CLL is further amplified in the presence of ZAP-70.