Immulonogy B Cells

Humoral Immunity

The aspect of adaptive immunity involving B cells that produce antibodies and cytokines to recognize native extracellular antigens.

Bone Marrow

The primary lymphoid organ where B cells arise in adult mammals and undergo antigen-independent maturation and gene rearrangement.

VDJ Recombination

An antigen-independent phase in the early stages of B and T cell development where segments of DNA—Variable (V), Diversity (D), and Joining (J)—are randomly rearranged.

RSS (Recombination Signal Sequences)

Genetic motifs consisting of a heptamer-spacer-nonamer where VDJ recombination is initiated by the RAG1/2 complex.

Allelic Exclusion

A process during development where a functional heavy or light chain rearrangement prevents the other chromosome from rearranging

Naïve B Cell

A mature B cell that has exited the bone marrow but not yet encountered antigen; it typically expresses both IgM and IgD on its surface.

T-cell Dependent Activation

The activation pathway for B cells responding to peptide antigens

T-cell Independent Activation

A pathway where B cells are activated by polysaccharide antigens without the need for T-cell assistance.

Germinal Centers

Specialized areas within lymph nodes where B cells proliferate and undergo affinity maturation and isotype class switching.

Somatic Hypermutation

An antigen-dependent process in the periphery that introduces point mutations into the V regions of Ig genes to further diversify the response.

AID (Activation-induced cytidine deaminase)

A specific enzyme that introduces nicks in transcribing DNA to facilitate somatic hypermutation and class switching.

Affinity Maturation

The selective process in germinal centers that generates B cells with a higher binding affinity for an antigen from cells with lower initial affinity.

Class Switching

An antigen-dependent process where a B cell changes the constant region of its antibody to produce different isotypes like IgG

Plasma Cell

A short-lived effector B cell specialized for secreting large quantities of antibodies (up to 2000 per second) into the blood or tissues.

Memory B Cell

A long-lived cell produced in germinal centers that maintains the same BCR specificity as its parent cell to provide a rapid secondary immune response.

CDR3 (Complementarity Determining Region 3)

The specific region within the variable domain that displays the highest degree of variability and is critical for antigen binding.

Neutralization

An antibody function where the binding of specific antibodies to bacterial toxins or viruses prevents them from affecting host cells.

Opsonization

A process where antibodies coat a pathogen to facilitate its recognition and ingestion by phagocytes like macrophages.