Adaptive Immunity Part 2 - B Cell Response

Flashcards covering early and advanced B cell responses, germinal center reactions, antibody classes and functions, T cell-independent responses, and B cell involvement in endodontic infections.

Primary B cell responses are initiated in secondary lymphoid organs, specifically the draining lymph nodes, spleen, or __________ nearest to the infection site.

mucosa-associated lymphoid tissue (MALT)

In lymph nodes, __________ sinus macrophages capture lymph-borne antigens and display them intact on their cell surface for naïve B cells to inspect.

subcapsular

B cells recognize intact antigens directly through their B cell receptors, whereas T cell receptors recognize pathogen-derived peptides presented on __________ class II molecules.

MHC

The initial antibodies produced during the early stage of a primary infection are predominantly of the __________ isotype.

IgM

To receive help from activated helper T cells at the B cell-T cell boundary, B cells internalize antigen via BCR and present processed peptides on __________ molecules.

MHC class II

Co-stimulation during T cell-B cell interaction requires B7 on the B cell binding to CD28, and CD40 on the B cell binding to __________ on the activated helper T cell.

CD40L

Activated B cells undergo clonal proliferation and differentiate into antibody-secreting cells called __________ cells.

plasma

The lower stem portion of a Y-shaped antibody molecule that interacts with receptors on phagocytes is called the __________ region.

Fc

The two arms of an antibody molecule responsible for binding specific antigens are called the __________ regions.

Fab

Maximum amino acid sequence diversity within the variable region of an antibody occurs in three hypervariable loops known as __________.

Complementarity-Determining Regions (CDRs)

The predominant antibody class in human serum, making up approximately $80\%$ of total serum immunoglobulins, is __________.

IgG

The only immunoglobulin class capable of crossing the placenta to provide passive immunity to the fetus is __________.

IgG

Secreted IgA typically forms a __________ structure linked by a J chain in mucosal secretions.

dimer

Pentameric IgM molecules adopt a __________ conformation upon binding repetitive antigens on bacterial surfaces, exposing C1q-binding sites.

staple

Somatic hypermutation of immunoglobulin variable region genes occurs in the __________ zone of the germinal center.

dark

During affinity maturation, B cells with mutated BCRs undergo positive selection in the light zone by interacting with antigens displayed on __________.

Follicular dendritic cells (FDCs)

The essential enzyme required for initiating both somatic hypermutation and class switch recombination in activated B cells is __________.

activation-induced cytidine deaminase (AID)

Cytokine-driven class switching from IgM to IgG is predominantly induced by __________.

IFN-\gamma

Cytokine-driven class switching to IgE is induced by the cytokine __________.

IL-4

Repetitive non-protein antigens like bacterial lipopolysaccharide (LPS) activate B cells through a T cell-__________ pathway.

independent

T cell-independent B cell responses produce predominantly IgM antibodies and fail to generate long-lived __________ B cells.

memory

Due to their large size ($150\,\text{kDa}$), IgG antibodies cannot penetrate intact cell membranes, making them ineffective against __________ pathogens.

intracellular

Spleen-resident __________ zone B cells specialize in rapid T cell-independent IgM production against blood-borne antigens.

marginal

In carious human teeth, immunoglobulins IgG, IgM, and IgA localize specifically along the walls of __________ tubules.

dentinal

In mice subjected to endodontic infection, the absence of B cells leads to severe orofacial __________ formation and potential mortality.

abscess

In germinal centers, specialized CD4+ T cells that provide survival and selection signals to B cells are called T __________ helper cells.

follicular