B-1 cell

Notably, most B-1 cells do not develop into memory B cells.

B-1 cells are a sub-class of B cell lymphocytes that are involved in the humoral immune response.

In specimens where the tyrosine kinase for Pyk-2 has been knocked-out, marginal zone B-cells will fail to develop while B-1 cells will still be present.

B-1 cells express IgM in greater quantities than IgG and its receptors show polyspecificity, meaning that they have low affinities for many different antigens.

B-1 cells are present in low numbers in the lymph nodes and spleen and are instead found predominantly in the peritoneal and pleural cavities.

B-1 cells generate diversity mainly via recombinatorial recombination (there is a preferential recombination between D-proximal VH gene segments).

CD5 is a cluster of differentiation found on a subset of IgM-secreting B cells called B-1 cells, and also on T cells.

B-1 cells have limited diversity of their B-cell receptor due to their lack of the enzyme terminal deoxynucleotidyl transferase (TdT) and are potentially self-reactive.

CD5 serves to mitigate activating signals from the BCR so that the B-1 cells can only be activated by very strong stimuli (such as bacterial proteins) and not by normal tissue proteins.

They are not part of the adaptive immune system, as they have no memory, but otherwise, B-1 cells perform many of the same roles as other B cells: making antibodies against antigens and acting as antigen presenting cells (APCs).

B-1 cells are first produced in the fetus and most B-1 cells undergo self-renewal in the periphery, unlike conventional B cells (B-2 cells) that are produced after birth and replaced in the bone marrow.