Introductory Microbiology: Innate Immunity, Adaptive Immunity, and Vaccination

Vocabulary practice flashcards covering innate defenses, adaptive humoral and cellular immunity, antibody structures, vaccines, hybridoma technology, and immune system disorders from Lectures 15, 16, and 17.

Innate Immunity

Nonspecific, immediate actions of the host immune system that defend against any pathogen and prevent infection without conferring immunological memory. First- and second-line defenses.

Susceptibility

Lack if resistance to a disease

Immunity

Ability to ward off disease by activating immune responses and preventing pathogen invasion. It is caused by previously encountered pathogens.

Nonspecific cellular attacks

Phagocytes and Complement

Physical factors in First line of defense

Skin, Mucous membranes, Ciliary escalator, Lacrimal apparatus, Saliva, Urine, Heat

Ciliary Escalator

A physical defense mechanism of the respiratory system in which microbes trapped in mucus are propelled upwards away from the lungs by ciliated cells.

Lacrimal Apparatus

The physiological structures that manufacture and drain tears to continually wash microbes and irritating substances away from the surface of the eye.

Chemical Factors in First line of defense

Lysosomes, low pH of gastric juice(1.2-3), acidity of vaginal lumen, Fungistatic fatty acid in sebum, transferrin in blood( limit iron available to microbes)

Lysozyme

An antimicrobial enzyme present in perspiration, tears, saliva, nasal secretions, and tissue fluids that destroys bacteria by enzymatically degrading bacterial cell walls.

Microbial Antagonism (Competitive Exclusion)

The protective biological action of the normal resident microbiota that outcompetes invading pathogens for available space and nutrients.

Immune System

contains components from circulatory, lymphatic, and reticulo-endothelial (RES) systems

Primary Lymphoid Organs

Bone marrow and Thymus which are the sites of maturation for B and T cells

Secondary Lymphoid Organs

Spleen, Lymph nodes, and Mucosal associated lymphoid tissue (MALT) which are the sites where lymphocyte-antigen interactions occur that trigger an adaptive immune response

Hematopoiesis

The developmental process by which pluripotent hematopoietic stem cells in the bone marrow differentiate into mature blood cell lineages, including erythrocytes, platelets, and leukocytes.

Neutrophils

Phagocytic granulocytes with a 3–5 lobed nucleus that comprise $50\text{--}70\%$ of healthy adult leukocytes, mediating the respiratory burst following phagocytosis.

Basophils

Granulocytes comprising $0.5\text{--}1\%$ of circulating leukocytes characterized by coarse blue histamine-containing granules that mediate allergic and inflammatory responses.

Eosinophils

Bilobed granulocytes comprising $1\text{--}4\%$ of leukocytes containing large orange-red granules that mediate defenses against helminth parasites and participate in allergic reactions.

Monocytes

Agranulocytic leukocytes with a large bean-shaped nucleus that comprise $2\text{--}7\%$ of adult white blood cells and circulate before migrating into tissues to develop into macrophages.

Dendritic cells

Initiate adaptive immune response

Lymphocytes

involved with specific immunity, (Natural killer/NK cells, B-cells, T-cells)

Differential Count

determine proportion of each WBC type that can suggest different types of infection

Phagocytosis

The cellular ingestion and breakdown of microbes or extracellular particles, performed by specialized cells such as neutrophils, macrophages, and dendritic cells.

Phagolysosome

The internal digestive vesicle formed by the fusion of a phagosome with a lysosome, where enzymes and reactive oxygen species destroy the engulfed microbe.

Microbial evasion of phagocytosis

some microbes can survive phagocytosis by inhibiting leukocyte function. they can produce toxins that kill leukocytes, inhibit the formation of phagolysosome, have a capsule that inhibits phagocytosis, and lyse the phagosome membrane to get released in the cytoplasm

Inflammation Function

mobilize phagocytic cells and direct them to site of injury to contain and eliminate pathogens and repair tissue damage to go back to normal

Inflammation Steps

Acute phase proteins released, vasodilation, margination, diapedesis, tissue repair

Vasodilation

mast cells secrete additional proinflammatory molecules including histamine leads to redness and heat

Diapedesis

The process during an inflammatory response in which phagocytic leukocytes squeeze between endothelial cells of the capillary wall to reach infected or damaged tissues.

Margination

The adhesion of phagocytes to the endothelial lining of blood vessels triggered by inflammatory mediators prior to extravasation.

Acute inflammation

only a few days and primarily involves neutrophils and monocytes, usually good

Chronic inflammation

Persisting inflammation that leads to host damage and may require surgical excision, usually bad

Ex. hepatitis, granulomas, abscesses

Complement system

a complex system of more than 30 proteins that are present in blood and tissues throughout the body that bind to microbes or the antibodies on the microbes and cause opsonization, inflammation, and phagocytosis

Complement Activation / Membrane Attack Complex (MAC)

A transmembrane pore formed by the sequential assembly of complement proteins $C5b$, $C6$, $C7$, $C8$, and multiple $C9$ fragments that causes osmotic cytolysis of target microbes.

Opsonization

The enhancement of phagocytosis resulting from the coating of an antigen or pathogen with proteins such as complement component $C3b$ or antibodies.

Interferons (IFNs)

Anti-viral proteins produced by virus-infected host cells ($\text{IFN-}\alpha$, $\text{IFN-}\beta$) or lymphocytes ($\text{IFN-}\gamma$) that stimulate antiviral protein synthesis in neighboring cells and activate macrophages.

Pathways to complement activation

Classical: Antibody binds to antigen on pathogen surface

Alternative: pathogen surface creates a local environment conducive to complement activation

Adaptive Immunity

A specific host defense system characterized by immunological memory and antigen-specific responses mediated by $B$ lymphocytes, $T$ lymphocytes, and antibodies.

Antigens (Ag)

triggers the body to produce antibodies

Antibodies(Ab)

Proteins made in response to antigen

Humoral immunity

involves antibodies produced by B cells that recognize antigens through the antibodies on the surface

B-cell origin

the stem cells develop and differentiate in the red bone marrow

Cell-mediated immunity

involves T cells that recognize antigens through receptors on their surface

T-cells origin

stem cells that develop in bone marrow or fetal liver that have ot go through the thymus to differentiate

Epitope (Antigenic Determinant)

A specific chemical group or structural region on an antigen surface that is recognized and bound by a complementary antibody or lymphocyte receptor.

Hapten

An epitope with low immunogenicity that cannot stimulate an immune response alone, requiring conjugation to a larger carrier protein to trigger antibody production.

Fc Region

The constant 'stem' portion of an antibody molecule that binds to complement proteins or surface receptors on host cells such as macrophages and natural killer cells.

Immunoglobulin G (IgG)

The predominant monomeric antibody class in human serum ($80\%$) that neutralizes toxins, crosses the placenta, activates complement, and provides long-term immunity.

Immunoglobulin A (IgA)

A dimeric antibody linked by a $J$ chain and a secretory component that comprises $13\%$ of serum antibodies and protects mucous membranes in tears, saliva, sweat, mucus, and colostrum.

Immunoglobulin M (IgM)

A pentameric antibody joined by a $J$ chain that comprises $6\%$ of serum antibodies, serving as a first-responder immunoglobulin in the primary immune response and fixing complement efficiently.

Immunoglobulin E (IgE)

A monomeric immunoglobulin that constitutes approximately $0.002\%$ of serum antibodies, functioning primarily in allergic responses and defense against parasitic worm infections.

Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

An Ag-Ab binding consequence. A protective mechanism wherein large parasites or infected host cells coated with antibodies are destroyed externally through the release of perforin and lytic enzymes by eosinophils, macrophages, or NK cells.

Clonal Deletion

The apoptotic destruction of autoreactive $B$ and $T$ lymphocytes during immune development to eliminate self-reactive clones and establish self-tolerance.

Plasma Cell

A terminally differentiated, antibody-secreting $B$ lymphocyte characterized by an abundant rough endoplasmic reticulum.

Helper T ($T_H$) Cells

CD4+ $T$ lymphocytes that recognize exogenous antigens presented on MHC class II molecules and secrete cytokines to activate $B$ cells, cytotoxic $T$ cells, and macrophages.

Cytotoxic T Lymphocytes (CTLs)

Effector CD8+ $T$ cells that recognize foreign or abnormal antigens presented on MHC class I molecules and trigger apoptosis in infected or transformed host cells via perforin and granzymes.

Major Histocompatibility Complex (MHC)

Cell surface glycoproteins that display antigen fragments to $T$ cells; MHC Class I presents endogenous antigens to CD8+ $T$ cells, whereas MHC Class II presents exogenous antigens to CD4+ $T$ cells.

Variolation

scabs from smallpox patients to induce immunity, Edward Jenner and the milkmaids

Provirus

The viral DNA genome of HIV that integrates into the host cell chromosomal DNA via integrase, establishing a latent infection or directing new virion production.

Clinical AIDS

The final stage of progressive HIV infection defined clinically when the host CD4+ $T$ cell blood concentration falls below $200\text{ cells/}\mu\text{l}$.

Vaccination

The administration of a non-virulent antigen to stimulate an adaptive immune response and induce immunological memory against a targeted pathogen.

Variolation

An early inoculation practice originating in China over 3,000 years ago that used scabs or fluid from smallpox pustules to stimulate immunity in uninfected individuals.

Live Attenuated Vaccine

A vaccine formulation containing viable, weakened pathogens that replicates without causing illness, inducing a potent cell-mediated response and long-lasting immunity.

Toxoid Vaccine

A vaccine containing inactivated bacterial exotoxins that stimulates neutralizing antibodies against toxin-mediated diseases such as tetanus and diphtheria.

Conjugated Vaccine

A vaccine created by attaching a poorly immunogenic capsular polysaccharide antigen to a protein carrier to enhance the adaptive immune response.

Adjuvant

A compound, such as an aluminum or calcium salt, added to a vaccine formulation to enhance general immune responsiveness to the target antigen.

Herd Immunity

The indirect protection from infectious disease extended to unvaccinated individuals when a large proportion of the population is immune.

Hybridoma

An immortal, cloned cell line generated by fusing a specific antibody-producing $B$ cell with a cancerous myeloma cell, used for mass production of monoclonal antibodies.

Monoclonal Antibodies (mAbs)

Homogeneous antibodies produced by a single clone of hybridoma cells that are uniform in structure and bind specifically to a single epitope.

Severe Combined Immunodeficiency (SCID)

A primary genetic immunodeficiency characterized by the absence or failure of both functional $B$ and $T$ cells, often caused by defects in the IL-2 gamma receptor (X-SCID) or adenosine deaminase (ADA-SCID).

Systemic Lupus Erythematosus (SLE)

A chronic autoimmune disease in which autoantibodies attack double-stranded DNA, causing a butterfly facial rash, arthritis, chest pain, and fatigue.

Graves' Disease

An autoimmune disorder characterized by autoantibodies targeting the thyroid-stimulating hormone (TSH) receptor, resulting in hyperthyroidism, goiter, and exophthalmos.