B Cells

Developed from hematopoietic stem cells, the Pro B Cell is the earliest lineage stage of the B Cell. The main goal and checkpoint of the Pro B Cell stage is the proper construction of a heavy chain rearrangement, leading to the Pre B Cell stage.

Human Markers

Positive: CD10, CD19, CD24, CD34, CD38, CD123, CD127, EBF1, Pax5

Negative: c-kit low, IgM

Mouse Markers

Positive: B220, CD19, CD24, CD43, CD127, E2A, EBF1, Pax5

Negative: BP-1, c-kit low, Flt3, IgM

Developed from Pro B cells, Pre B Cells express a proper heavy chain (µ) paired with surrogate light chains (VpreB and λ5) in their pre B Cell receptor. This step is crucial to development, as only B Cells expressing this pre B Cell receptor are allowed to progress to the next stage, the Immature B Cell.

Human Markers

Positive: CD10, CD19, CD20, CD24, CD38, CD123, CD124, CD127, E2A, EBF1, Oct2, Pax5

Negative: CD34, c-kit, IgM

Mouse Markers

Positive: B220, BP-1, CD19, CD24, CD25+/-, CD43 low, CD127, E2A, EBF1, Pax5, Siglec G

Negative: c-kit, IgM

The Immature B Cell stage is characterized with the rearrangement of a proper light chain. This membrane bound IgM antibody is then paired with Ig-α and Ig-β to form a fully functioning B Cell receptor. Before progressing to a mature state, the cells must not react strongly to self. If they recognize self, they may have the chance to perform receptor editing to pass inspection.

Human Markers

Positive: CD10, CD19, CD20, CD21, CD24 hi, CD38 hi, CD40, CD124, IgM, EBF1, Pax5

Negative: CD27, CD127,c-kit, IgD

Mouse Markers

Positive: B220, BP-1, CD19, CD24, CD93, E2A, EBF1, IgM, Oct2, Pax5

Negative: CD23, CD43, IgD

Transitional B Cells represent an almost intermediary state between Immature B Cells in the bone marrow and Mature B Cells in the periphery. Divided into T1 and T2 stages, these cells can be found in the bone marrow, blood, and spleen, giving rise to Marginal Zone and Follicular B Cells.

Human Markers

Positive: CD5, CD19, CD20, CD21, CD24 hi, CD38 hi, E2A, EBF1, IgM, Oct2, Pax5

Negative: CD10 low, CD27, IgD low

Mouse Markers

Positive: B220, BP-1, CD19, CD21+/-, CD23+/-, CD24, CD93, E2A, EBF1, IgM, Oct2, Pax5

Negative: IgD low

Upon exiting the bone marrow, Mature B Cells will express both IgM and IgD on their cell surface. At this point, the cells will have acquired functional competence, hence their title of “mature”. They may be called naïve if they have not yet encountered their specific antigen.

Human Markers

Positive: CD19, CD20, CD25, CD27, CD30, CD69, CD80, CD86, CD135, EBF1, IgD, IgM, Pax5

Mouse Markers

Positive: B220, BP-1, CD27, CD69, CD80, Flt3, IgD, IgM, MHC II hi, Pax5

Negative: CD138, CXCR4

Regulatory B Cells, or Bregs, are a subtype of B Cells capable of downregulating inflammation and inducing tolerance. However, these cells can be phenotypically difficult to identify, as they bear many common markers found on other B Cell types. The most well studied Bregs may be the B-10 and T2-MZP (Transitional 2 Marginal Zone Precursor) population. Many Breg subclasses execute their immunosuppression through IL-10.

Human Markers

Positive: CD1d hi, CD5, CD19, CD21 hi, CD24 hi, E2A, EBF1, IgD+/-, IgM hi, Oct2, Pax5

Negative: CD27+/-

Mouse Markers

Positive: CD1d hi, CD5, CD19, CD24, E2A, EBF1, IgD, IgM hi, Oct2, Pax5, Tim-1

Negative: CD62L, CD93+/-

B-1 Cells are considered an innate lymphocyte that appears early on in the development of the host. This has led to their being named “B-1,” while conventional B Cells that appear later on are termed “B-2”. B-1 Cells make up roughly 5% of mouse and human total B cell population. B-1 Cells arise from stem cell populations and exhibit the ability to self-renew. As they can also express a limited range of “natural”, lower-affinity antibodies, do not undergo affinity maturation, do not require T Cell help, and do not have a proclivity to develop into Memory B Cells. All of this lends credence to the theory they are mainly involved with quick, innate immune responses.

As seen below, phenotyping B-1 cells can be difficult. We recommend taking a look at this reference for more information.

Human Markers

Positive: CD5+/-, CD11b+/-, CD19, CD20, CD27, CD43, CD86+/-, IgD, IgM

Negative: CD70

Mouse Markers

Positive: CD5, CD9+/-, CD11b, CD19, CD21, CD38, CD43, CD80, CD273+/-, IgM hi, IL-5R

Negative: IgD low

Follicular B Cells can be found within structures called follicles (which contain germinal centers) in secondary and tertiary lymphoid organs like the spleen, Peyer's patches, and lymph nodes. Unlike Marginal Zone B Cells, Follicular B Cells are capable of recirculating throughout the body. They are capable of becoming either Memory B Cells or Long Lived Plasma Cells. In most instances, these cells require T Cells for full activation.

Human Markers

Positive: CD19, CD20, CD21, CD22, CD23, CD24, E2A, EBF1, IgD, Oct2, Pax5

Negative: CD10, CD24 low, CD27, CD38 low, IgM low

Mouse Markers

Positive: B220, CD19, CD22, CD23, E2A, EBF1, CD38, IgD, Oct2, Pax5

Negative: CD1d low, CD21/35 low, CD93, IgM low

Marginal Zone (MZ) B Cells are a mature form of B Cells that home specifically to the MZ of the spleen. As such, they specifically guard against blood-borne pathogens they would be likely to encounter in the spleen. They typically have a lower threshold of activation compared to Follicular B Cells and can develop into Short Lived Plasma Cells, generating “natural antibodies” in a T Cell independent manner.

Human Markers

Positive: CD1c, CD19, CD20, CD21 hi, CD27+/-, E2A, EBF1, Oct2, Pax5

Negative: IgD low

Mouse Markers

Positive: B220, CD1d, CD9, CD21 hi, CD22 hi, CD35 hi, E2A, EBF1, IgM, Oct2, Pax5

Negative: CD23, CD93, IgD low

Upon encountering antigen, Mature B Cells can develop into plasmablasts, which further differentiate into Plasma Cells. As indicated by their names, Short Lived Plasma Cells (SLPC) only persist for a few days, rapidly churning out antibody before undergoing apoptosis. SLPCs can typically be found in the red pulp of the spleen or in medullary chords of lymph nodes.

Human Markers

Positive: CD27, CD138, CD269

Negative: CD19 low, CD20, MHC II low

Mouse Markers

Positive: Blimp-1, CD93, CD138, CXCR4 hi

Negative: B220 low, CD19, CD38 low, MHC II low

Memory B Cells develop after a primary infection within the host. After encountering an antigen, a subset of cells that developed from an individual cell can retain the experience and memory of its target. This leads to a quicker immune response should that antigen should ever reintroduce itself to the body.

Human Markers

Positive: CD19, CD20, CD27+/-, CD40, CXCR4, CXCR5, CXCR7, Pax5, SPI-B

Negative: CD23 low, CD38

Mouse Markers

Positive: B220, BP-1, CD38+/-, CD62L+/-, CD80+/-, IgA, IgE, IgM, Pax5, SPI-B

Negative: CD95 low, IgD

Upon encountering antigen, Mature B Cells can develop into plasmablasts, which further differentiate into Plasma Cells. Plasma Cells are, quite frankly, powerhouses of antibody production. They generate a single class of immunoglobulin designated for a specific antigen. Antibody production can continue for days or months until the target is neutralized.

Human Markers

Positive: CD27, CD38 hi, CD138, CD269, CXCR4, IRF4, XBP1

Negative: CD19 low, CD20, MHC II, Surface Immunoglobulins

Mouse Markers

Positive: CD138, CXCR4 hi, IRF4, XBP1

Negative: B220 low, CD19, CD38 low, MHC II, Surface Immunoglobulins