MIDTERM STUDY GUIDE:

Flashcards covering key vocabulary related to Innate Immune Defenses, Hematopoiesis, Roles of Innate Immune Cells, Lymphoid Tissue, Complement Pathways, Cytokines & Chemokines, Adaptive Immunity, B & T Cells, MHC, Immunoglobulins, and T cell Development.

Skin

A physical innate immune defense that prevents microbial entry into the body.

Antimicrobial proteins (Lysozymes)

Chemical innate immune defenses that digest bacterial cell walls.

Antimicrobial peptides (Defensins)

Chemical innate immune defenses that disrupt bacterial and viral membranes.

Phagocytosis

A process of extracellular pathogen destruction by phagocytes like macrophages and neutrophils.

Phagosome

An endosome containing an engulfed pathogen, formed during phagocytosis.

Phagolysosome

Formed by the fusion of a phagosome and a lysosome, containing low pH and digestive enzymes to destroy pathogens.

PAMPs (Pathogen Associated Molecular Patterns)

Molecular patterns on microbes (e.g., bacterial cell wall components, nucleic acids) that are recognized by innate immune cells.

PRRs (Pattern Recognition Receptors)

Receptors on innate immune cells (like macrophages) that recognize PAMPs.

Cytokines

Secreted proteins that act as signaling molecules in the immune response.

Chemokines

A type of cytokine that acts as chemoattractants to recruit immune cells to a site of infection.

B cell

An innate immune cell that differentiates into plasma cells and produces antibodies.

T cell

An innate immune cell that differentiates into cytotoxic T cells (attack pathogens) and helper T cells (activate other cells).

Dendritic cell

A phagocytic cell that acts as an antigen-presenting cell and is important for pathogen destruction and initiating adaptive immunity.

Macrophage

A phagocytic cell that releases cytokines, participates in apoptosis, and presents antigens.

Neutrophil

A type of granulocyte that performs phagocytosis and is recruited to sites of infection.

Antigen Presenting Cells (APCs)

Cells like dendritic cells, macrophages, and B-cells that present antigens to T cells.

Primary Lymphoid Tissue

Sites like bone marrow and the thymus where B and T cells develop and mature.

Secondary Lymphoid Tissue

Sites like lymph nodes and the spleen where antigens activate lymphocytes.

MALT (Mucosa Associated Lymphoid Tissue)

Specialized secondary lymphoid tissue found in the mucus membranes of digestive, respiratory, and urogenital tracts.

Peyer's Patch

A specialized MALT located in the small intestine and ileum, acting as an immune sensor and initiating IgA production.

Complement System

A cascade of proteins that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells.

MAC (Membrane Attack Complex)

A component of the complement system that ruptures bacterial cell walls, leading to cell lysis.

Opsonization (Complement)

The process where complement proteins (e.g., C3a) tag pathogens for destruction by phagocytes like neutrophils and macrophages.

C5a

An anaphylatoxin and chemokine derived from C5 cleavage that attracts neutrophils and macrophages.

NFkB pathway

An extracellular signaling pathway activated upon ligand binding to cell-surface receptors, leading to the transcription of cytokine genes like IL-1 and TNF-α.

Interferons (IFN-α, IFN-β)

Cytokines that play a role in antiviral defense, attracting NK cells and stimulating production of other antiviral proteins.

Innate Immunity

A non-specific type of immunity present from birth, involving cells and defenses created during development.

Adaptive Immunity

A specific type of immunity learned after contact with a pathogen, characterized by immune memory and specific recognition of antigens.

Humoral Immunity

An aspect of adaptive immunity mediated by B cells and antibodies that bind to and neutralize pathogens.

Cell-mediated Immunity

An aspect of adaptive immunity mediated by T cells that use T cell receptor proteins to recognize antigens.

Immune Memory

A feature of adaptive immunity where daughter B and T cells quickly and effectively combat future infections by the same pathogen, often leveraged by vaccines.

Cytotoxic T cells (CD8)

A type of T cell that directly attacks and destroys pathogen-infected cells.

Helper T cells (CD4)

A type of T cell that activates and supports other immune cells to combat pathogens.

T cell receptors (TCRs)

Transmembrane proteins that are heterodimers of α-chain and β-chain, used by T cells to bind to specific peptides presented by MHC molecules.

MHC (Major Histocompatibility Complex)

Cell surface molecules that present peptide fragments of antigens to T cells.

MHC Class I

Presents peptides from intracellular pathogens (e.g., viruses) to CD8+ T cells.

MHC Class II

Presents peptides from extracellular pathogens (acquired externally) to CD4+ T cells.

Immunoglobulins (antibodies)

Proteins that function as B cell receptors when expressed on the cell surface, or as secreted soluble molecules that neutralize, opsonize, or activate immune components.

Isotype Switching (Class Switching)

A process in B cells where the heavy chain constant region genes recombine, resulting in the production of different types of antibodies (e.g., from IgM to IgG, IgA, or IgE).

Somatic Hypermutation

A process that allows B cells to improve the binding affinity of their antibodies to antigens, also known as affinity maturation.

Primary Immune Response

The immune system's first reaction to an antigen, which can take weeks to clear an infection and leads to the formation of memory cells.

Secondary Immune Response

A rapid and stronger immune response upon subsequent encounters with the same antigen, mediated by memory cells, clearing the antigen within days.

Thymus

A primary lymphoid organ where T cells (thymocytes) develop and mature, undergoing crucial selection processes.

Double Negative Thymocyte

An immature T cell in the thymic cortex that does not express CD4 or CD8 and begins TCR somatic recombination.

Double Positive Thymocyte

A thymocyte that expresses a fully rearranged TCR along with both CD4 and CD8 co-receptors, undergoing positive and negative selection.

Positive Selection (Thymus)

A process in the thymic cortex that selects thymocytes whose TCRs can bind with low or intermediate affinity to self-MHC molecules presented by cortical thymic epithelial cells.

Negative Selection (Thymus)

A process in the thymic medulla that eliminates thymocytes whose TCRs bind too tightly to self-MHC peptide complexes, preventing autoimmunity.

AIRE (Autoimmune Regulator)

A transcriptional activator that allows medullary thymic epithelial cells to express a wide range of 'self' genes, enabling negative selection against tissue-specific antigens.

Lineage Commitment

The process by which a double positive thymocyte commits to expressing a single coreceptor, either CD4 or CD8, to become a single positive T cell.