Ab initio.

From the beginning.

B cells are a lineage of lymphocytes originally discovered in the Bursa of Fabricus in birds (hence the B in B cells). B cell development in mammals was mainly found to occur in the bone marrow, as they do not have a Bursa of Fabricus. B cells are not only responsible for antibody production, but are also involved in several other areas of immunology. Click through the different sections of the shield to gain an understanding of everything B cells do in a mammalian system.

Want help designing your B Cell panel? Click here!

Nulla tenaci invia est via.

For the tenacious, no road is impassable.

Click on a cell below to learn more about it.

Pro B Cell

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: CD10CD19CD24CD34CD38CD123CD127, EBF1, Pax5

Negative: c-kit lowIgM


Mouse Markers


Positive: B220CD19CD24CD43CD127, E2A, EBF1, Pax5

Negative: BP-1, c-kit lowFlt3IgM

Pre B Cell

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: CD10CD19CD20CD24CD38CD123CD124CD127, E2A, EBF1, Oct2, Pax5

Negative: CD34c-kitIgM


Mouse Markers


Positive: B220, BP-1, CD19CD24CD25+/-CD43 lowCD127, E2A, EBF1, Pax5, Siglec G

Negative: c-kitIgM

Immature B Cell

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: CD10CD19CD20CD21CD24 hiCD38 hiCD40CD124IgM, EBF1, Pax5

Negative: CD27CD127,c-kitIgD


Mouse Markers


Positive: B220, BP-1, CD19CD24CD93, E2A, EBF1, IgM, Oct2, Pax5

Negative: CD23CD43IgD

Transitional B Cell

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: CD5CD19CD20CD21CD24 hiCD38 hi, E2A, EBF1, IgMOct2, Pax5

Negative: CD10 lowCD27IgD low


Mouse Markers


Positive: B220, BP-1, CD19CD21+/-CD23+/-CD24CD93, E2A, EBF1, IgM, Oct2, Pax5

Negative: IgD low

Mature B Cell (Activated)

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: CD19CD20CD25CD27CD30CD69CD80CD86CD135, EBF1, IgDIgMPax5


Mouse Markers


Positive: B220, BP-1, CD27CD69CD80Flt3IgDIgMMHC II hi, Pax5

Negative: CD138CXCR4

Breg Cell

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 hiCD5CD19CD21 hiCD24 hi, E2A, EBF1, IgD+/-IgM hiOct2Pax5

Negative: CD27+/-


Mouse Markers


Positive: CD1d hiCD5CD19CD24, E2A, EBF1, IgDIgM hi, Oct2, Pax5Tim-1

Negative: CD62LCD93+/-

B-1 Cell

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+/-CD19CD20CD27CD43CD86+/-IgDIgM

Negative: CD70


Mouse Markers


Positive: CD5CD9+/-CD11bCD19CD21CD38CD43CD80CD273+/-IgM hiIL-5R

Negative: IgD low

Follicular B Cell

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: CD19CD20CD21CD22CD23CD24, E2A, EBF1, IgDOct2, Pax5

Negative: CD10CD24 lowCD27CD38 lowIgM low


Mouse Markers


Positive: B220CD19CD22CD23, E2A, EBF1, CD38IgD, Oct2, Pax5

Negative: CD1d lowCD21/35 lowCD93IgM low

Marginal Zone B Cell

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: CD1cCD19CD20CD21 hiCD27+/-, E2A, EBF1, Oct2Pax5

Negative: IgD low


Mouse Markers


Positive: B220CD1dCD9CD21 hiCD22 hiCD35 hi, E2A, EBF1, IgM, Oct2, Pax5

Negative: CD23CD93IgD low

Short Lived Plasma Cell

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: CD27CD138CD269

Negative: CD19 lowCD20MHC II low


Mouse Markers


Positive: Blimp-1CD93CD138CXCR4 hi

Negative: B220 lowCD19CD38 lowMHC II low

Memory B Cell

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: CD19CD20CD27+/-CD40CXCR4CXCR5CXCR7Pax5, SPI-B

Negative: CD23 lowCD38


Mouse Markers


Positive: B220, BP-1, CD38+/-CD62L+/-CD80+/-IgAIgEIgMPax5, SPI-B

Negative: CD95 lowIgD

Long Lived Plasma Cell

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: CD27CD38 hiCD138CD269CXCR4IRF4XBP1

Negative: CD19 lowCD20MHC IISurface Immunoglobulins


Mouse Markers


Positive: CD138CXCR4 hiIRF4XBP1

Negative: B220 lowCD19CD38 lowMHC IISurface Immunoglobulins

Incepto ne desistam

May I not shrink from my purpose!

Ense petit placidam sub libertate quietem.

By the sword, she seeks a serene repose under liberty.


Antibodies are one of the chief products of B cells and plasma cells. Antibodies are also known as immunoglobulins, which is why they begin with the abbreviation Ig. In mammals, the letters A, D, E, G, and M are assigned based on the particular heavy chain (α, δ, ε, γ, µ respectively). While the basic components of antibodies are the same (2 light chains, 2 heavy chains), they can serve different functions. Click on each isotype to learn more about each type.


Crescat scientia vita excolatur.

Let knowledge grow, let life be enriched.


To learn more about B Cells, check out the following pages:

Maturation Markers

How to Make an Antibody

Basic Immunology

Cell Markers



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