B Cell Development

Question 1

Pluripotent stem cell

Answer 1

An undifferentiated cell that has the capability of becoming any type of cell

Question 2

Hematopoietic cell

Answer 2

A cell that has differentiated to become a type of blood cell. Hematopoietic stem cells that have the capability of becoming any type of blood cell including cells in the myeloid and lymphoid cell lineages.

Question 3

Pro B cell

Answer 3

A developing B cells in the bone marrow that is the earliest cell committed to the B lymphocyte lineage. The pro-B cell has undergone Dh to Jh rearrangement on the heavy chain locus.

Question 4

Pre B cell

Answer 4

A developing B cell present only in hemtopoietic tissues that has rearranged heavy chain genes, but no rearranged light chain genes. A pre-B cell expresses an invariant surrogate light chain and Ig-mu heavy chain at its surface in conjunction with the signal transduction molecules Ig-alpha and Ig-beta; these molecules together make up the pre-B cell receptor complex. The pre-B cell receptor complex delivers signals that stimulate further maturations of the pre-B cell into an immature B cell.

Question 5

Immature B cell

Answer 5

A developing B cell that expresses IgM on its surface but does not express IgD. The IgM+ and IgD- B cell does not proliferate or differentiate in response to antigens; instead, the cell may undergo apoptotic death or become functionally unresponsive if it recognizes an antigen. This process is important for the negative selection of B cells that are specific for self-antigens present in the primary lymphoid organs.

Question 6

Mature B cells

Answer 6

A B-cell expressing IgM and IgD on its surface. These B-cells populate peripheral lymphoid organs.

Question 7

Surrogate light chain

Answer 7

The surrogate light chain associates with the mu heavy chain on the surface of pre-B cells during the development of a B lymphocyte. The surrogate light chain is encoded by two non-rearranging genes, lambda 5 and Vpre-B.

Question 8

Clonal deletion

Answer 8

The apoptotic death of an immature T cell in the thymus or an immature B cell in the bone marrow as a consequence of recognizing an abundant self antigen found in the respective organ. Clonal deletion is one mechanism in the development of immune self-tolerance.

Question 9

Anergy

Answer 9

A state of unresponsiveness to stimulation by a specific antigen. When clones of T or B cells fail to react to a particular antigen, this is termed lymphocyte anergy. Lymphocyte anergy (also called clonal anergy) likely serves as a mechanism of maintaining immunologic tolerance to self. Clinically, anergy manifests as a lack of T cell-development cutaneous delayed-type hypersensitivity reaction to a common antigen.

Question 10

Receptor editing

Answer 10

A process by which an immature B cell that recognizes self-antigens in the bone marrow may undergo a change in antigen specificity. During receptor editing, the RAG genes are reactivated, producing additional light chain VJ recombinations, thus leading to the production of a new Ig light chain. This allows the cell to express a different Ig receptor that is not self-reactive. Receptor editing is one mechanism for maintaining self-tolerance.

Question 11

Autoreactive antibodies

Answer 11

These antibodies are specific for a self-epitope and can result in autoimmune disease

Question 12

Plasma cell

Answer 12

A terminally differentiated antibody-secreting B lymphocyte. Mature B cells are stimulated to become plasma cells as a result of reaction with a specific antigen.

Question 13

Somatic hypermutation (SHM)

Answer 13

Random point mutations that occur in this variable region of the B cell receptor genes during clonal expansion in a germinal center of a secondary lymphoid organ. SHM is dependent on the protein AID and is important in the process of affinity maturation.

Question 14

Memory cells

Answer 14

Differentiated B or T lymphocytes that are initially produced via antigen stimulation of naive lymphocytes during a primary immune response. In subsequent exposures to the same antigens, memory cells mediate rapid and enhanced immune responses. Memory B and T cells are able to survive in a functionally quiescent state for many years between antigen exposure.

Question 15

Ig-alpha and Ig-beta

Answer 15

Proteins required for surface expression and signaling functions of membrane Ig on B cells. The B cell receptor is composed of Ig-alpha and Ig-beta chains that are linked to each other via disulfide bonds and are noncovalently associated with the membrane-bound Ig molecule.

Question 16

Signal transduction

Answer 16

A process where a cell converts a message or stimulus to another type of message or stimulus. Signal transduction frequently refers to the conversion of an extracellular message to a molecular cascade within the cell.

Question 17

Antiserum

Answer 17

Serum from an individual previously exposed to an antigen that contains antibody specific for that antigen. Antiserum can be used in the prevention, treatment, or diagnosis of infectious disease.

Question 18

Polyclonal antibodies

Answer 18

A collection of antibodies that have different epitope specificity. Antibodies collected from antiserum are typically polyclonal because any given antigen typically has many epitopes.

Question 19

Monoclonal antibodies

Answer 19

Antibodies with the same specificity that are all the progeny of a single B cell.

Question 20

Hybridomas

Answer 20

A cell formed by the fusion of an immortal cancer cell with an antibody-producing plasma cell. Hybridomas are used as a means of generating monoclonal antibodies for research, diagnostics, and therapeutics.

Question 21

Chimeric antibodies

Answer 21

A genetically engineered antibody, typically originated in a mouse, that has had the mouse constant region sequences exchanged for human constant region sequences. This is one methods used to produce monoclonal antibodies for human therapeutic purposes.

Question 22

Humanized antibodies

Answer 22

A genetically engineered antibody that utilizes only the complement determining regions (CDRs) of an antigen-specific mouse antibody and inserts those CDR sequences into human immunoglobulin genes.