Immune System Notes

Comprehensive vocabulary flashcards covering the components, functions, cellular mechanisms, and molecular defenses of the innate and adaptive immune systems.

Pathogen

A micro-organism that can produce disease in a host by invading and releasing toxins.

Antigen

An "ID tag" (antibody generating) molecule that can be classified as a foreign antigen ("foreign tag") or self-antigen ("self tag").

Innate Immune System

The non-specific "first line of defense" immune response active in $<4\text{ days}$, composed of physical, chemical, and cellular defenses.

Acquired Immune System

An adaptive (antigen-specific) immune response found only in vertebrates that acts as the "last line of defense" (typically taking $>4\text{ days}$).

Dead Skin

A physical barrier of the innate immune system that prevents microbes from entering the body.

Mucus

A slippery, gel-like fluid that lines and protects the respiratory, digestive, urinary, and reproductive tracts.

Interferon

A chemical defense (such as Type 1) that causes interference of viral replication.

Histamine

A chemical released by cells, such as mast cells, that causes inflammation and promotes an immune response.

Pyrogen

A chemical defense that causes fever in order to denature pathogens' proteins and promote immune cell reproduction.

Complement Proteins

A group of $50+$ normally inactive proteins that, when triggered by antibodies, increase inflammation and release chemicals to kill pathogens.

Perforin

A chemical that causes target cell membranes to form pores, resulting in cell lysis.

Granulocytes

A group of white blood cells comprising $60\text{--}70\%$ of cellular defenses, including neutrophils, mast cells, and natural killer cells.

Neutrophil

A type of granulocyte making up approximately $60\%$ of all white blood cells that kills pathogens via phagocytosis once and then dies.

Mast Cell

An innate immune cell that does not kill pathogens directly, but sends signals to promote immune responses and releases histamine.

Natural Killer Cell

An innate cytotoxic cell that kills pathogens not via phagocytosis, but by releasing the pore-forming chemical perforin.

Monocytes

White blood cells comprising $1\text{--}6\%$ of cellular defenses that use generic Toll-like Receptors (TLRs) to identify pathogens.

Toll-like Receptors (TLRs)

Generic receptors found on monocytes used to identify pathogens.

Macrophage

A monocyte-derived "big eater" capable of consuming up to $100$ microbes via phagocytosis before dying.

Dendritic Cell

A phagocytic cell that kills pathogens and displays fragments of invaders to alert adaptive immune cells.

Antigen Presenting Cell (APC)

A cell that uses MHC molecules on its cell surface to display fragments of invaders, alerting T-cells to launch a targeted adaptive immune response.

Major Histocompatibility Complex II (MHC II)

A "self" antigen complex found exclusively on white blood cells (antigen-presenting cells).

Major Histocompatibility Complex I (MHC I)

A "self" antigen complex found on non-white blood cells (nucleated body cells).

Lymphocytes

Adaptive immune cells comprising $20\text{--}30\%$ of white blood cells, primarily consisting of B-lymphocytes and T-lymphocytes.

Clonal Selection

A process explaining how a single B or T cell that recognizes an entering antigen is selected from a pre-existing pool of diverse specificities and reproduced to generate a clonal population that eliminates the antigen.

B-Lymphocytes

Lymphocytes originating in bone marrow that identify specific antigens and produce highly specific antibodies to bind them for destruction.

Plasma B Cells

Effector B-lymphocytes that actively produce and secrete antibodies at a rate of approximately $2{,}000\text{ antibodies per second}$.

Memory B Cells

Long-lived B-lymphocytes formed through clonal selection that remain in the body to launch a rapid antibody response upon reinfection.

T-Lymphocytes

Lymphocytes that originate in bone marrow and mature in the thymus to identify and kill pathogens.

Helper-T Cell

A T-lymphocyte that coordinates the immune response by regulating the activity of cytotoxic T cells and B lymphocytes through cytokine signaling.

Cytotoxic T Cells

"Killer cells" that directly eliminate virus-infected cells, intracellular microbes, and cancer cells by secreting perforin and cytotoxins.

Humoral Response

The branch of adaptive immunity that uses antibodies circulating in body fluids to target and eliminate extracellular pathogens like bacteria and toxins.

Cell-Mediated Response

The branch of adaptive immunity specialized to tackle threats hiding inside host cells, destroying virus-infected cells, microbes, and cancer cells.

1. Tag antigen

2. Neutralization

3. Agglutination

4. Precipitation

5. Complement protein activation.

Antibody Effects

IgM

Pentamer

serving as "first responder" (Main)

located primarily in blood and lymphatic fluid.

IgA

Dimer

acting as a "secretory defender" (assistant)

found in saliva, tears, mucus, sweat, and breast milk.

IgD

Monomer

a B-cell activator ("divide & conquer").

located on the surface of B-cells

IgG

monomer

accounting for $80\%$ of all antibodies (General)

located in blood, bodily fluids, and able to cross the placenta to the fetus.

IgE

A monomer

binds to parasites and allergens (eliminate)

located on mast cells, skin, lungs, and mucosal membranes.

Live Attenuated Vaccine (LAV)

utilizing a weakened live pathogen, exemplified by Tuberculosis (BCG), Oral polio vaccine (OPV), Measles, Rotavirus, and Yellow fever vaccines.

Inactivated Vaccine

omposed of killed pathogens, exemplified by Whole-cell pertussis (wP) and Inactivated polio virus (IPV).

Subunit Vaccine

uses purified antigen components, including Acellular pertussis (aP), Haemophilus influenzae type B (Hib), Pneumococcal (PCV), and Hepatitis B (HepB).

Toxoid Vaccine

A vaccine containing inactivated bacterial toxins, such as Tetanus toxoid (TT) and Diphtheria toxoid.

Salty

allows for the dehydration of microbes

pH

Acidic/low to kill off microbes (5 for skin 2 for stomach)

Hair/Fur

proteins attract polar dust particles and microbes

Native Microbial Community

inhibits foreign microbes to invade

1. Fight disease causing pathogens

2. recognize and neutralize harmful substances

3. neutralize malfunctioning self cells (cancer/senescent)

Function of Immune System

1. Tag antigen

Bind to specific antigen

Neutralization

1. Inhibit pathogen activity

2. Puts so much antibodies on the pathogen to not do anything

Agglutination

1. The pathogens stick together 

2. Antibodies can connect to 2 pathogens and connect them together

Precipitation

1. To clump

2. The body believes a foreign body is inside so the antibodies surround it 

Complement Protein Activation

Target pathogens

1. Binding Site

2. Variable Site

3. Constant Site

Parts to antibody

Immunoglobulin (MADGE)

Types of antibodies