Fundamentals of Stem Cells and Immunology Flashcards

A comprehensive set of vocabulary flashcards covering the fundamentals of immunology, including cell types, signaling pathways, and the adaptive immune system mechanisms as described in the lecture notes.

Cluster of differentiation (CD)

Molecules recognized by groups of antibodies, forming a "cluster" numbered from $CD1$ to $CD372$.

Mast Cells

Long-lived resident cells found in peripheral tissues (skin, lung, gut) that degranulate to release cytokines, histamines, or other inflammatory mediators in response to allergies.

Eosinophils

Cells found in peripheral tissues (respiratory, gastrointestinal, and genitourinary tracts) that contain pre-formed cytoplasmic granules for defense against parasites such as helminths.

Basophils

Blood granulocytes that are functionally and structurally similar to mast cells and release histamine and heparin to prevent blood clotting.

Neutrophils

Short-lived blood granulocytes with potent antibacterial functions (defensins) that can produce NETS (exploding DNA and chromatin) to trap pathogens.

Monocyte / Macrophages

Long-lived professional APCS and resident tissue cells (e.g., Microglia in the CNS, Kupffer cells in the liver) that secrete cytokines such as $TNF-\text{α}$, $IL-1$, $IL-6$, $IL-8$, and $IL-12$.

Dendritic Cells

Cells that initiate the adaptive immune response by detecting PAMPS through a range of receptors and activating $CD4$ and $CD8$ T cells.

Innate Lymphoid cells (ILCs)

Cells residing in epithelial tissue that produce cytokines; they are divided into five major groups including NK cells, Group 1 ILC ($ILC1$), $ILC2$, and $ILC3$.

Hematopoiesis

The process by which all circulating blood cells arise in the bone marrow.

AIRE (auto immune regulator)

Specialized cells in the thymus medullary epithelial cells (MEC) that produce tissue-specific or peripheral tissue-specific antigens.

Spleen

A highly vascularized abdominal organ containing sinusoids where blood-borne antigens are trapped and processed by abundant phagocytes.

PAMPs (Pathogen-associated molecular patterns)

Molecular patterns expressed by microbes that are recognized by pattern recognition receptors (PRR).

DAMPs (Danger-associated molecular patterns)

Molecules released from damaged or necrotic cells that trigger an immune response.

Toll-like receptors (TLRs)

Membrane-bound receptors specific for different microbial components; for example, $TLR-4$ recognizes LPS and $TLR-5$ recognizes bacterial flagellin.

NOD receptors

Cytoplasmic sensors (e.g., $NOD1$ and $NOD2$) that recognize bacterial cell wall components such as DAP or MDP and activate $NF-\text{κ}B$ via the adaptor molecule $RIPK2$.

NF-kB ($NF-\text{κ}B$)

The key signaling pathway for inflammation that induces the expression of inflammatory genes following the degradation of the inhibitor $I\text{κ}B$.

Complement System

A cascade of sequential proteolytic cleavage of complement proteins that assists the anti-microbial activity of antibodies; it includes Alternative, Classical, and Lectin pathways.

MAC (Membrane attack complex)

A late-step complement assembly consisting of $C5b$, $C6$, $C7$, $C8$, and Poly-$C9$ that forms a pore in the plasma membrane to cause cell lysis.

Epitopes

Also known as antigenic determinants, these are small, often linear parts of pathogens that bind to antigen-specific receptors on T cells.

MHC Class I

Molecules expressed by all nucleated cells that present intracellular antigens to $CD8+$ cytotoxic T lymphocytes (CTL).

MHC Class II

Molecules expressed only on professional APCS (and some non-professional ones) that present extracellular antigens to $CD4+$ helper T cells.

Cross-presentation

A process unique to professional APCs where exogenous antigens are processed and presented on MHC class I to activate $CD8+$ T cells.

V(D)J Recombination

The random rearrangement of Variable (V), Diversity (D), and Joining (J) gene segments mediated by the recombinase enzymes $RAG-1$ and $RAG-2$ to create BCR and TCR diversity.

Isotype switching

A T-dependent process where B cells change the constant region of their heavy chain (e.g., from $IgM$ to $IgG$, $IgA$, or $IgE$) based on cytokine signals.

Affinity maturation

The process where B cells undergo somatic hypermutation of $Ig$ V genes followed by selection to increase the affinity of the antibody for a specific antigen.

Chemokines

Cytokines (such as $CCL19$, $CCL21$, or $CXCL13$) that stimulate cytoskeletal changes and coordinate the migration and homing of leukocytes.

Defensins

Hydrophobic pore-forming peptides widely expressed by mucosal epithelial cells and specialized anti-microbial cells (PMNs) to clear infections.