Generation of Antigen Receptors & Lymphocyte Development

Vocabulary flashcards based on lecture notes about the immune system and antibody diversity.

Rag Enzyme

A DNA shuffling enzyme that targets the genes responsible for making antibody binding sites in B cells, creating diversity.

V, D, and J Segments

Gene segments (Variable, Diversity, and Joining) that are randomly combined by Rag to create diverse antibody heavy chains.

Hypervariable Region

The region within the antibody binding site where nucleotides are added or removed during gene segment joining, leading to immense antibody diversity.

Complementarity Determining Regions (CDRs)

The specific contact points within the hypervariable region of an antibody that directly interact with and recognize the protein antigen.

Recombination Signal Sequence (RSS)

DNA sequences flanking gene segments that signal to the RAG complex where to cut and recombine DNA during V(D)J recombination.

Junctional Diversity

Diversity created by the addition or subtraction of nucleotides at the junctions between gene segments during V(D)J recombination.

Terminal Deoxynucleotidyl Transferase (TdT)

An enzyme that adds random nucleotides to the ends of the DNA strands during V(D)J recombination, increasing junctional diversity.

Somatic Recombination

The process by which separated gene segments are joined together to form a functional immunoglobulin or T cell receptor gene.

Signaling Joint

A circular piece of DNA that is created and removed from the cell during V(D)J recombination; it plays no further role in the process.

Combinatorial Diversity

The diversity in antibodies and T cell receptors created by the different possible combinations of V, D, and J gene segments.

Negative Selection

The process by which T cells or B cells that strongly recognize self-antigens are eliminated in the thymus or bone marrow to prevent autoimmunity.

Central Tolerance

The state of immunological tolerance that is established centrally during lymphocyte development.

AIRE (Autoimmune Regulator)

A transcription factor expressed in the thymus that allows the presentation of tissue-restricted antigens, facilitating negative selection of autoreactive T cells.

Positive Selection

The process in the thymus where T cells that can recognize self MHC molecules are selected to survive, ensuring MHC restriction.

MHC Restriction

The property of T cells that they can only recognize antigens when presented by the individual's own MHC molecules.

Clonal Selection

The process by which antigen-specific lymphocytes are activated and proliferate to generate an army of effector cells and memory cells.

Effector Cells

Lymphocytes that actively combat pathogens and include cytotoxic T cells, helper T cells, and plasma cells.

Memory Cells

Long-lived lymphocytes that remain in the body after an infection and mount a rapid response upon subsequent encounters with the same antigen.

T Cell Receptor (TCR)

A receptor on the surface of T cells that recognizes antigen fragments bound to MHC molecules on antigen-presenting cells.

Antigen-Presenting Cells (APCs)

Cells such as dendritic cells, macrophages, and B cells that display antigen fragments complexed with MHC molecules on their surface, activating T cells.

Co-stimulatory Molecules

Surface molecules on APCs that bind to receptors on T cells, providing a second signal required for T cell activation.

Cytokines

Signaling molecules secreted by immune cells that regulate immune responses and mediate cell-to-cell communication.

Interleukin-2 (IL-2)

A cytokine produced by T cells that promotes T cell proliferation and differentiation.

CD4+ T Cells

Helper T cells that express the CD4 co-receptor and recognize antigen fragments presented on MHC class II molecules.

CD8+ T Cells

Cytotoxic T cells that express the CD8 co-receptor and recognize antigen fragments presented on MHC class I molecules.

MHC Class I Molecules

Molecules present on all nucleated cells that present antigen fragments derived from intracellular pathogens to CD8+ T cells.

MHC Class II Molecules

Molecules present on APCs that present antigen fragments derived from extracellular pathogens to CD4+ T cells.

Cross-presentation

The process by which some APCs present exogenous antigens on MHC class I molecules, activating CD8+ T cells.

T Helper 1 (Th1) Cells

A subset of CD4+ T cells that produce cytokines such as IFN-γ and activate macrophages and cytotoxic T cells.

T Helper 2 (Th2) Cells

A subset of CD4+ T cells that produce cytokines such as IL-4 and IL-5 and activate B cells and promote antibody production.

T Helper 17 (Th17) Cells

A subset of CD4+ T cells that produce IL-17 and promote inflammation and defense against extracellular pathogens.

T Regulatory (Treg) Cells

A subset of CD4+ T cells that suppress immune responses and maintain immune tolerance.

Foxp3

A transcription factor essential for the development and function of Treg cells.

B Cell Receptor (BCR)

A membrane-bound antibody molecule on the surface of B cells that recognizes and binds to specific antigens.

Plasma Cells

Differentiated B cells that secrete large quantities of antibodies.

Antibody Isotypes

Different classes of antibodies (IgG, IgM, IgA, IgE, IgD) that have distinct functions and are produced in response to different types of antigens.

Class Switching

The process by which B cells switch from producing one antibody isotype to another, allowing for tailored immune responses.

Affinity Maturation

The process by which B cells produce antibodies with progressively higher affinity for the antigen during a prolonged immune response.

Somatic Hypermutation

A process in which B cells introduce point mutations into the variable regions of their antibody genes, leading to improved antigen binding.

Long-Lived Plasma Cells

Plasma cells that reside in the bone marrow and continuously secrete antibodies for many years, providing long-term immunity.