. Author manuscript; available in PMC: 2020 Apr 24.

Published in final edited form as: Leukemia. 2018 Dec 16;33(2):287–298. doi: 10.1038/s41375-018-0303-x

Table 1.

IgM and IgD isotype expression and function in normal B cells and CLL cells.

BCR isotype	Expression in normal B cells	Function in normal B cells	Expression in CLL cells	Function in CLL cells
IgM	Expressed at the immature B-cell stage after productive VDJ recombination ⁵; secreted or membrane-bound	Lower threshold for B-cell activation¹³; down-modulated in vivo following chronic antigen exposure ²⁰	Higher levels on U-CLL, as compared to M-CLL ^{27, 38, 39}	Survival and proliferation^{49, 59, 60}, cell cycle entry⁴⁹, long-lived signaling activation ⁴⁹; cross-talk with CXCR4⁴⁴, TLR signaling ⁴⁵ and IL-4 ⁴⁶; higher IgM responsiveness in U-CLL ^{27, 38, 39}
IgD	Co-expressed with IgM in mature B-cells⁵; secreted or membrane-bound; contains a hinge region necessary to polyvalent antigen binding ¹³	Higher threshold for B-cell activation¹³; lower association with the CD19 co-receptor ¹⁶	Co-expressed with IgM^{27, 38, 39}	Short-lived signaling and cytoskeletal activation, rapid internalization ^{48, 49}