Immune Systems

Immunology

the study of the immune system, a complex network of cells, tissues, and organs that work together to protect the body from harmful pathogens and other foreign substances

Innate Immunity

defenses that function against a broad array of microbes

Adaptive immunity

immune response that is produced in response to a specific foreign antigen

Antigen

something that stimulates an adaptive immune response: non-self, something your immune system identifies as non-self, tell the difference between what is self and what is non-self

First Line Defenses

Barriers that separate the interior of the body from the environment

Physical barriers

Skin: stratified epithelium and ciliated columnar epithelium cells

Mucous membranes

will trap microorganisms in mucus, muco-ciliary escalator, respiratory tract, and the cilia cause mucus to flow upwards (cough, sneeze, or expel upwards so they don't remain in lungs)

Flushing mechanisms

peristalsis of G1 contracts of intestinal tract, moves through the out

Lysozyme

breaks down the cell walls of bacteria, making it an important part of the body's innate immune system. It's found in many bodily secretions, like tears, saliva, and mucus

Lactoferrin

bind iron (crucial for bacterial metabolism and growth)

Fatty acids

have antimicrobial properties

Acidic environments

make it difficult for microbes to grow

Normal flora

microbes that normally inhabit body surfaces

Microbiome

everyone has their own, takes up all the parking spots, a potential pathogen will attach (first step) if it can't attach, can't affect

Stem cells

formed in bone marrow, hematopoietic stem cells, develop and mature to be any type of blood cell

Hematopoiesis

the process of forming blood cellular components

Colony stimulating factors

will cause a stem cell to differentiate and become specific type of stem cell

White blood cells (Leukocytes)

cells of the immune system that help the body fight infections

Granulocytes

Eosinophils, basophils, neutrophils; cytoplasm looks grainy

Agranulocytes

Monocytes, Lymphocytes (T cells and B cells); cytoplasm does not look grainy

Phagocytes

to eat, engulf and destroy foreign antigen (neutrophils, monocytes, macrophages, dendritic cells)

Natural Killer (NK) cells

have the ability to identify infected or abnormal cells and then kill them, does not have to be activated first

B cells

develop in bone marrow, become plasma cells when activated, secrete antibody, adaptive immunity

T cells

develop in thymus

T helper

coordinates immune response

T cytotoxic

kill infected and abnormal cell, has to be activated first

CBC

complete blood cell count, possible to look at sample of blood and differentiate different types of white blood cells, half will be neutrophil

Macrophages

tissues associated phagocyte, search tissue for foreign antigen

Dendritic cell

similar to macrophages, found in tissues, such as the skin, and boosts immune responses by showing antigens on its surface to other cells of the immune system

Cell surface receptors

Bind ligands that produce a cellular response.

Cytokines

Signaling molecules for immune response.

Chemokines

Induce chemotaxis, movement of cells in response to a chemical.

Colony stimulation factors

Differentiation of a stem cell to a specific type of blood cell.

Interferons

Antiviral, induce fever, inflammation.

Interleukins

Produced by leukocytes, typically cause a response to leukocytes.

Tumor necrosis factors

Involved in inflammation and apoptosis (programmed cell death).

Pattern recognition receptors

Detect foreign agents, including PAMPs and DAMPs.

PAMPs

Pathogen associated molecular patterns, peptidoglycan, only found in bacteria.

DAMPs

Damage associated molecular patterns, indicate cellular damage caused by pathogens.

Toll-like receptors

Designed to detect different bacterial PAMPs and DAMPs on the surface.

NOD-like receptors

Detect PAMPs and DAMPs within the cell.

RIG-like receptors

Detect viral PAMPs and DAMPs.

Complement System

Proteins that circulate in the bloodstream, designed to detect foreign antigens.

Classical pathway

Activated by the presence of antigen (antibody complexes, proteins produced by adaptive immunity).

Alternative pathway

Activated when complement protein C3b binds to microbial surface.

Lectin pathway

Activated when mannose binding protein binds to mannose on potential pathogens.

C3

Gets split in half to form C3a and C3b.

C3a

A chemokine that attracts white blood cells and stimulates inflammation.

C3b

Enhances phagocytosis by binding to microbial surfaces.

C5

Can be split into C5a and C5b.

C5a

A chemokine that stimulates inflammation.

C5b

Stimulates the membrane attack complex, causing lysis of the target cell membrane.

Phagocytosis

The process of binding foreign antigens and engulfing and destroying them.

Monocyte

A type of white blood cell that differentiates into macrophages and dendritic cells.

Neutrophils

A type of phagocyte that is the first responder to sites of infection.

Macrophages

Phagocytes that are derived from monocytes and are found in tissues.

Dendritic cells

Antigen-presenting cells that act as messengers between the innate and adaptive immune systems.

Phagocytes

Cells that can engulf and digest pathogens and debris.

C3b receptors

Receptors on phagocytes that bind to complement protein C3b to enhance phagocytosis.

Phagosome

A membrane-bound vesicle that contains a pathogen after it has been engulfed by a phagocyte.

Lysosomes

Organelles that contain proteases and oxidizing agents to digest pathogens.

Phagolysosome

A structure formed by the fusion of a phagosome with a lysosome to degrade microbes.

Inflammation

A biological response to harmful stimuli, characterized by swelling, redness, heat, and pain.

PAMPs and DAMPs

Pathogen-associated molecular patterns and damage-associated molecular patterns that trigger inflammation.

Toll-like receptors

Receptors that recognize PAMPs and DAMPs, leading to the release of pro-inflammatory cytokines.

Pro-inflammatory cytokines

Signaling molecules released to initiate and propagate the inflammatory response.

C3a and C5a

Complement proteins that attract white blood cells to sites of infection.

Coagulation cascade

A series of events that lead to blood clotting and tissue repair following damage.

Vasoactive cytokines

Cytokines that affect blood vessel behavior, initially causing constriction followed by vasodilation.

Diapedesis

The process by which leukocytes exit the bloodstream to reach sites of infection.

Acute inflammation

A short-term inflammatory response characterized by neutrophil predominance and tissue healing.

Chronic inflammation

A prolonged inflammatory response characterized by macrophage predominance and ongoing tissue damage.

Septic shock

A severe inflammatory response to endotoxin leading to rapid blood pressure loss and organ failure.

Sepsis

A systemic inflammatory response to PAMPs and DAMPs that is not localized.

Interferons

Proteins produced by cells in response to viral infections that help to alert neighboring cells.

Pyrogens

Substances that induce fever, which can be exogenous (from outside the body) or endogenous (produced by the body).

Adaptive Immunity

The immune response that is specific to a particular antigen and involves memory cells.

Memory cells

Cells that remain in the body after an infection and can respond more rapidly upon re-exposure to the same antigen.

Primary response

Adaptive response on first exposure, first time encounter, takes a while to develop specific immune response.

Secondary response

Subsequent exposures, reactivate memory cell to eliminate the antigen, you don't even get sick.

Humoral immunity

Mediated by B cells, secrete antibody that bind to specific antigen.

Extracellular antigens

Primarily against extracellular antigens, exogenous/extracellular antigen.

Cellular Immunity

Mediated by T cells.

Intracellular antigens

Primarily against intracellular antigens, endogenous/intracellular.

Antigens

Any molecule that interacts with antibodies or lymphocytes.

Immunogen

Stimulates an immune response, broad term.

Antigenic determinants (epitopes)

Small portion of a molecule that stimulates response.

Antibodies

Proteins made up of 4 polypeptides, found on surface of B cells.

IgG

Maternal to fetal.

IgM

1st, B cell receptor; first class of antibody that is secreted by plasma cell.

IgD

B cell receptor; found on surface of B cell.

IgE

Antibodies that bind to allergens and cause symptoms.

IgA

Protect against pathogens that infect through mucus membranes.

Variable region

Epitope binding site, has 2 binding sites that are identical, recognize the same epitope.

Opsonization

Enhance phagocytosis; phagocytes have Fc receptors, coat bacterial cell with antibodies.

Activation of complement

Complement protein to the antibody leads to inflammation and lysis of foreign cell.

Antibody dependent cellular cytotoxicity

Antibody can be recognized by natural killer cells.

Neutralization

Binding of antigen by antibody does not directly 'kill' the antigen, marks it for destruction.

Agglutination/precipitation

Given antibody molecule has 2 epitope binding sites, clumps of antigen to make it easier to eliminate.

B cells

Use antibody molecules, IgM and IgD, on their cell surface to bind extracellular (exogenous) antigens.