Life of a B cell

Central Lymphoid Tissue

Stem cell

Lymphoid progenitor cell

Precursor B cell

–          Surrogate light chain

Immature B cell

 

Spleen: major site of immune response to blood-borne antigens

Immature B cell

–          Follicular dendritic cell (tissue macrophage?)

Mature (naïve) B cell

–          Mostly rest in primary follicles in peripheral lymphoid tissue

–          Recirculate (around 2x /day)

 

Peripheral Lymphoid Tissue

–          Lymphocytes enter the lymph node through HEV in the paracortex

–          Enter the spleen through the central arteriole which is surrounded by the white pulp (PALS)

Primary follicles

–          Resting Mature B cell

Secondary follicles have germinal centers

–          Develop in response to antigenic stimulation of B cells

–          Site of B cell proliferation, selection (high affinity Ab), generation of memory B cells

–          See page 95

LN Medulla

–          Plasma cells secreting Ab

 

Activation

Antigen recognition

–          The mature naïve B cell phagocytoses the antigen and presents the epitope

–          Present antigen to Helper T cell

–          Activates Helper T cell; Helper T cell activates B cell

–          Clonal expansion, isotype switching, affinity maturation, differentiation

 

Proliferate in response to antigens

–          Most progeny B cells differentiate in antibody-secreting plasma cells

Plasma cell

–          Found mostly in extrafollicular sites of peripheral lymphoid organs & at inflammatory sites

–          All Igs produced have the same idiotype & isotype; same specificity as the BCR on the parent B cell

Live only a few days (3-6) and then die.

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