Lecture 2: Immunity & Infection

first line of defense

portion of innate immunity that consists of:

- microbes

- skin (& secretions)

- mucous membranes (& secretions)

second line of defense

portion of innate immunity that consists of:

- phagocytic leukocytes

- antimicrobial proteins

- inflammatory response

- fever

third line of defense

adaptive immunity that consists of:

- lymphocytes

- antibodies

- memory cells

epidermis

outer layer of skin overlying the dermis

dermis

inner layer of skin that secretes antimicrobial peptides (AMPs) such as defensin

sweat glands

glands responsible for perspiration and produce salt, antimicrobial peptides, lysozyme (breaks sugar linkages), and RNAse (breaks down viral RNA)

mucous membranes

1 or more epithelial layers that cover all body cavities that are open to the outside environment

Goblet cells

specialized defensive cells of the respiratory system that release mucus (with mucin glycoproteins) and protect mucous membranes

clogs airways

impact of mucus hyper-secretion in bronchitis and asthma

cilia

cells in the respiratory system that sweep and clear mucus

saliva

contains enzymes (amylase) and lysozymes

stomach acid

highly acidic aspect of the digestive system; contains HCl and proteases

gastroferritin

iron-binding protein that sequesters iron from microbes

peristalsis

waves of muscle contraction in the digestive system that clears bacteria to prevent overgrowth

1) macrophages

2) neutrophils

3) dendritic cells

4) eosinophils

5) basophils

components of innate immunity

phagocytes

involved in innate immunity and are responsible for general defense against foreign/damaged particles and production of cytokines (which promote cell division)

macrophages

phagocytes that are formed from monocytes, reside in tissues, and are APCs (antigen presenting cells)

neutrophils

phagocytes that are the most abundant and found in blood

dendritic cells

phagocytes that are found on exposed internal surfaces and are APCs (antigen presenting cells)

eosinophils

aspect of innate immunity that proliferate during parasitic infections (ex: helminth) to secrete antimicrobial chemicals/toxins

basophils

aspect of innate immunity activated during infections and allergies

natural killer T cells

found both in innate and adaptive immunity; kill viral, infected, and cancer cells

B cells

lymphocytes that mature into plasma cells and produce antibodies

T cells

lymphocytes that can recognize antigens, produce cytokines, assist in maturation of immune cells, and mediate inflammation

lymphocytes

involved in adaptive immunity; help you remember pathogens and target them

humoral immunity

"body fluid" immunity by B cells involving antibody production (part of adaptive immune response)

cellular immunity

immunity by T cells involving the killing of infected cells (part of adaptive immune response)

acquired immunity

immunity you develop during your life (active or passive)

active immunity

immunity developed after infection or vaccination

natural active immunity

type of active immunity in which antibodies are made after exposure to an infection

artificial active immunity

type of active immunity in which antibodies are made after getting a vaccination

passive immunity

immunity you acquire from someone or something else (your body is not producing its own antibodies)

natural passive immunity

type of passive immunity in which antibodies are transmitted from mother to baby (ex: breast milk)

artificial passive immunity

type of passive immunity in which antibodies are acquired from an immune serum medication

pathogen

microorganism that is able to cause disease

pathogenicity

the ability to produce diseases in a host organism

virulence

the degree of pathogenicity of a microbe (depends on the ability to infect and cause damage); involves adherence, invasion, and toxin production

adherence

process by which bacteria stick to the surface of host cells (using factors like flagella, pili/fimbriae, and attachment proteins like adhesin and invasin)

invasion

process by which pathogens enter host cells or tissues and spread in the body; can occur via enzymes (collagenase, hyaluronidase, keratinase) or intracellularly via zipper/trigger mechanisms and immune phagocytosis

toxigenicity

the amount and type of toxin produced

Listeria

example of a bacteria that invades host cells using the zipper mechanism

Salmonella, Shigella

examples of bacteria that invades host cells using the trigger mechanism ("shooting" proteins into the cell using a secretion system)

animal reservoirs

mechanism of transmission of infection of microbes that primarily exist in animals and may incidentally infect humans through:

- contact (ex: petting, bats with coronavirus)

- eating (ex: Salmonella from chickens)

- insects (ex: Malaria from mosquitoes, bubonic plague from fleas, Lyme Disease from ticks)

human carriers

mechanism of transmission of infection through individuals that may be asymptomatic or have mild symptoms, enhancing possibility of transmission (ex: COVID carriers)

nonliving reservoirs

mechanism of transmission of infection that may be inadvertent (ex: soil, cholera in water, food, air, etc.)

coagulase

bacterial enzyme used to escape phagocytosis by triggering a blood clot, which shields the bacteria from phagocytes (ex: Staphylococcus aureus)

1) escape

2) preventing fusion of the phagosome with lysosomes (prevents digestion)

3) surviving in the phagolysosome

mechanisms through which bacteria can survive phagocytosis (after being taken into the endosome/phagosome)

exotoxin

a toxin (protein) that may be secreted by bacteria (Gram + and -) or released by cell lysis; damages host by destroying cells or disrupting metabolism (highly potent) and

DPT (DTaP/Tdap)

example of a vaccine important in the prevention of exotoxin-mediated disease

endotoxin

component of the outer membrane that is released upon cell lysis (only in Gram - bacteria); pathophysiologic effects when in blood stream:

- fever

- leukopenia (reduced WBC count)

- hypotension (low BP)

- shock (drop in blood flow)

- death

lipopolysaccharides (LPS) in the outer membrane

example of an endotoxin of E. coli

1) presence/absence of envelope

2) genome (DNA vs. RNA)

3) strands of nucleic acid (single strand vs. double strand)

classification of viruses

Influenza

example of an enveloped virus

Adeno

example of a non-enveloped virus

Adeno

example of a DNA virus

Corona

example of an RNA virus

tegument

cluster of proteins that lines the space between the envelope and nucleocapsid

1) attachment and entry (via endocytosis)

2) release of RNA

3) replicase proteins replicate RNA

4) structural proteins are used to form new viruses

5) maturation and release

steps in viral replication

1) cell fusion

2) metabolic alterations

3) host immune cell induced damage

4) host cell death

5) cell transformation into tumor cells (cancer)

impacts of viral pathogenesis

Acyclovir

viral base analog used to treat Herpes virus infections (inhibit viral polymerase)

viral proteases

cleave polyproteins to generate mature proteins for replication (can be targeted to stop viral replication)

Maraviroc

blocks HIV virus binding to host cells (blocks receptors)