B Lymphocytes

Author: V. Dimov, M.D., Fellow, Creighton University Division of Allergy & Immunology
Reviewer: S. Randhawa, M.D., Fellow, LSU (Shreveport) Department of Allergy & Immunology

B-cell development


Hematopoiesis. Image source: Wikipedia.

B-Cell Activation by Antigen (Ag)

Activation of B cells. Image source: Wikipedia.

The activation of B cells occurs when 2 Ig receptors are bridged (cross-linked) by antigen (Ag). This process transmits a signal to the cytoplasm via 2 molecules (Igα and Igβ). All these structures together form the B-cell antigen receptor (BCR) complex.

The T cells regulate B-cell proliferation and differentiation which takes 3-7 days. Thereafter, some activated B cells (called centroblasts) migrate deep into the lymphoid follicles and proliferate rapidly, forming the dark zone of the germinal center. B cells also give rise to a generation of plasma cells and memory B cells. Those memory B cell enables the host to mount a rapid and stronger secondary immune response with a subsequent encounter with the same antigen.


Germinal Centers. This video describes the formation and function of germinal centers. This video is from: Janeway's Immunobiology, 7th Edition, Murphy, Travers, & Walport. Source: Garland Science.


Lymphocyte Trafficking. This video describes how lymphocytes travel through the blood stream and into a lymph node. This video is from: Janeway's Immunobiology, 7th Edition, Murphy, Travers, & Walport. Source: Garland Science.

B-cells are the only cell types that synthesize antibody molecules.

CDs on Different Cells

CD25 and CD3 are found on all T cells. CD25 is a receptor for IL-2.

CD19 and CD21 are found on all B cells.

CD16 are found on natural killer (NK) and NK T cells. CD16 is a receptor for IgG.

IL7 activates naive T cells. BAF activates naive B cells.

Mnemonics

T cells have CD 3, 4 and 8 (double, 4 x 2)
B cells have CD 19, 20 and 40 (double 20 x 2)

Stem cell CD34+
Plasma cell CD 38+

Surface Markers

L
Ligands on
Lymphocytes

CD40L on T helpers (CD4+)
FAS-L on CTL 9CD8+)

CD40 on B cells
FAS ("death signal") on cells to be killed by CTLs


Gene Recombination. This video shows how gene recombination affects immunoglobulins. This video is from: Janeway's Immunobiology, 7th Edition Murphy, Travers, & Walport. Source: Garland Science.

References

Allergy and Immunology MKSAP, 3rd edition.

Related Reading

Medical Immunology Syllabus. Columbia University.
In the Clinic - Dr. Robert Wood, MD, Discusses the IgE Blood Allergy Test. InsiderMedicine.ca (video).
Variations in Receptor Gene Contribute to Asthma Exacerbations. Medscape, 01/2008; J Allergy Clin Immunol 2007;120:1285-1291.
Anti-IgE (omalizumab): A new therapeutic approach for chronic rhinosinusitis. JACI, Volume 121, Issue 1, Pages 257-258 (January 2008).
FIT Corner Q & A from 5th edition of Cellular and Molecular Immunology, edited by Abul K. Abbas and Andrew H. Lichtman. ACAAI, 2004.

Video

3D Medical Animation: Antibody Immune Response

Published: 12/13/2007
Updated: 05/05/2009