B-Cell Mediated Immunity II

A type of T cell that helps activate B cells to produce antibodies. They express CD40 ligand, which binds to CD40 on B cells, activating NF-κB and triggering B cell activation.

A process where B cells divide and multiply rapidly to produce more antibody-producing cells, called plasmablasts.

The area in a lymph node where B cells are concentrated; it is rich in chemokines that attract B cells.

A structure formed when a TFH cell interacts with a B cell, allowing communication and exchange of signals.

A small, mobile organelle that is crucial for directing the transport of proteins and other molecules in cells; it plays a vital role in the immunological synapse.

The process where immature B cells in the bone marrow undergo a selection process to ensure they do not react harmfully with the body's own tissues.

The process where immature B cells in the bone marrow are selected for their ability to bind to specific antigens.

A type of B cell that is fully mature and has not yet encountered its specific antigen.

The process where a B cell is activated by an antigen and begins to proliferate and differentiate into plasma cells and memory B cells.

Antigen-presenting cells that reside in secondary lymphoid tissues and help B cells capture and present antigens.

Specialized T cells that help activate B cells and promote their differentiation into plasma cells.

B cells that produce and secrete antibodies.

Long-lived B cells that are primed to respond quickly to a subsequent encounter with the same antigen.

A type of antigen that can directly activate B cells without the need for T cell help. These antigens are often multivalent and can cross-link multiple B cell receptors (BCRs) and co-receptors, triggering B cell activation.

TI-Antigens often induce the production of low-affinity IgM antibodies, which are mainly directed against common bacterial polysaccharides. These antibodies are considered a first line of defense against pathogens.

The process by which B cells differentiate into antibody-secreting plasma cells and their antibodies undergo affinity maturation and isotype switching.

Antigen-activated B cells that undergo further differentiation within germinal centers.

This protein protects centrocytes from apoptosis, allowing them to survive and continue differentiating.

The process by which B cells switch from producing one class of antibody (e.g., IgM) to another (e.g., IgG).

Highly repetitive DNA sequences located upstream of the constant region genes in the immunoglobulin locus.

An enzyme that catalyzes the conversion of cytosines to uracils in DNA, a critical step in isotype switching.

The removal of uracil residues from DNA during isotype switching.

This enzyme removes damaged bases from DNA, facilitating isotype switching.

A type of immune deficiency characterized by the inability to switch antibody classes due to mutations in the AID gene.

A cytokine that plays a key role in promoting terminal B cell differentiation and isotype switching.

The development of B cells into plasma cells that secrete high-affinity antibodies specific to an encountered antigen.

Mature B cells are capable of recognizing and responding to specific antigens by expressing both IgM and IgD B cell receptors.

The first encounter with an antigen triggers a cascade of events leading to the generation of plasma cells that secrete IgM antibodies and activate memory B cells.

The subsequent exposure to the same antigen triggers a faster and more robust immune response due to the presence of memory B cells, resulting in higher affinity antibodies mainly of the IgG isotype.

A complex of proteins that act as a receptor on the surface of B cells for specific antigens.

One part of the BCR complex, which is directly involved in recognizing the antigen, including IgM and IgD.

Two proteins (IgA and IgB) that are associated with the BCR, and play a crucial role in intracellular signaling.

A cluster of proteins that assists in B cell activation by co-recognizing certain antigens.

A protein that is a part of the B cell co-receptor, and recognizes components of the complement system, enhancing the immune response.

The process of B cells differentiating into specialized cells that rapidly proliferate and mature into plasma cells secreting IgM antibodies.

Activated B cells divide rapidly and form clusters within a follicle, creating a germinal center. This process is essential for the development of high-affinity antibodies.

In the germinal center, a subset of B cells called centroblasts stop expressing surface immunoglobulin and undergo somatic hypermutation, affinity maturation, and isotype switching. This leads to the creation of B cells with diverse V-region genes and different C-region genes, resulting in antibodies with different effector functions.

The germinal center has two distinct zones: the dark zone and the light zone. The dark zone is densely packed with centroblasts that rapidly divide. The light zone contains centrocytes that divide more slowly and are actively competing for access to TFH cells and antigen presented by FDCs.

Somatic hypermutation is a process that introduces point mutations randomly throughout the rearranged V domain coding sequence of the antibody genes, specifically targeting the hypervariable regions.

The hypervariable regions (HVs) are located within the variable domains (VL and VH) of antibody molecules and are responsible for antigen binding. Each VL or VH domain has three HVs, known as complementarity-determining regions (CDRs).

Activation-induced cytidine deaminase (AID) is an enzyme produced only in dividing B cells. It plays a crucial role in somatic hypermutation by converting cytosine to uracil in ssDNA during transcription.

Centrocytes with high-affinity BCRs are more likely to internalize and present antigen to TFH cells, as they can bind antigen with greater efficiency.

T follicular helper cells (TFH) recognize MHC-II:peptide complexes presented by activated centrocytes and bind to CD40 on the centrocyte. This binding event stimulates the centrocyte and drives antibody production.

Plasmablasts are activated B cells that are on the path to becoming fully differentiated plasma cells, the primary antibody-producing cells.