B cell development begins with hematopoietic stem cells in the bone marrow, progressing through stages such as Pro-B cell, Pre-B cell, Immature B cell, and Transitional B cell, leading to the formation of mature naive B cells. These cells can become activated upon antigen binding and differentiate into memory B cells or plasma cells. This process ensures diverse B cell specificities while preventing autoreactive clones.

IgM and IgD antibodies are unique as they can be expressed as both membrane-bound B cell receptors (BCRs) and secreted antibodies due to their close genomic organization. This allows naive B cells to have increased antigen recognition capacity. In contrast, other antibody isotypes require class switching in activated B cells to be expressed as secreted antibodies.

Germline genetic material is inherited and present in the zygote. Innate immune receptors like TLRs and NLRs are encoded by single germline genes. TCRs and BCRs genes are not directly encoded by germline genes, but rearranged randomly to create diverse TCR and BCR repertoire during T and B cell development. V(D)J recombination process introduces immense diversity.