The Immune System

Susceptibility

lack of resistance to a disease

Immunity

ability to ward off disease

Innate immunity

Non specific defense mechanisms that provide immediate defense against pathogens

Inflammation

the first response of the immune system to infection; stimulated by chemical factors released by injured cells

Pattern Recognition Receptors

Proteins that recognize something in the body that is not normally there

Inflammatory mediators

Histamine, leukotrienes, Bradykinin, Prostaglandins, Serotonin

Toll-Like Receptors

Germ-line encoded PRRs found on the surface of macrophages, mast cells, and dendritic cells that recognize pathogen markers

Nod-like receptors

sense infection and stress through cytoplasmic PAMPs- occurs INSIDE of the cell; typically leads to cell death and cytokines released

Pathogen associated molecular patterns

What PRRs typically use to detect something that isn’t meant to be there

RIG-I-Like Receptors & Cytosolic DNA Censor

PRRs for host antiviral reponses

C-Type Lectin Repeptors

PRRs for anti-fungal responses

Phagocytes

Cells that are able to do phagocytosis

Macrophages

most efficient phagocytes, releases respiratory bursts, stay in one area of body

Respiratory burst

a burst of oxygen and other molecules given out by some phagocytes that is toxic to any other bacteria surrounding it

Neutrophil

circulating phagocyte, respiratory, first to arrive at site of immune response

Dendritic Cells

Phagocytic cells present in tissues that are in contact with external environment

Mast Cells

Connective tissue and mucus membranes; histamine, heparin, chemokines

Basophiles

Histamine; attacks parasites, part of allergic reactions

Eosinophils

attacks worms and viral infections, part of allergic reactions

Natural Killer Cells

Destry compromised host cells that lack MHC expression; attacks viruses and cancers

γδ T-cells

Less common in humans, found in GI tract, alternative T-cell receptor

Complement System

Labels pathogens with C3b which can perforate the cell membrane, make it easier for macrophages to phagocyte, or make more inflammatory cells able to recognize it

Adaptive immunity

adaptive resistance to a specific pathogen

antigens

substances that can elicit a response form a B or T cell

Epitope

the small accessible part of an antigen that binds to an antigen receptor

Class I antigen presentation

Intracellular antigens; MHC class I

Class II antigen Presentation

Extracellular antigens; MHC class II

Dendritic Cell antigen presentation

Activated macrophages & B-cells

B-cell activation

B-cell antigen receptor binds to an antigen, antibodies are secreted that are similar to receptor but lacks transmembrane regions

Antibodies/Immunoglobulins

proteins that B-cells excrete that mark pathogens for destruction — B cells can express 5 forms

IgD

membrane bound Immunoglobulins

IgM

first soluble class of immunoglobulin produced

IgG

Second soluble class of immunoglobulin, most abundant

IgA and IgE

Remaining soluble classes of immunoglobulin

Normal T-Cell Receptor

αβ T-Cell Receptor

Cytotoxic T-cells receptors

CD8; perforin, granulysin, granzymes(apoptosis)

Helper/Regulatory T-cells Receptors

CD4; Th-1(intracellular), Th-2(extracellular)

Active Immunity

develops naturally when memory cells form clones in response to an infection; can be developed with immunzations

Passive immunity

Provides immediate, short-term protection, can be conferred naturally when IgG passes the placenta from mother to fetus or when IgA passes from mother to infant in breast milk; conferred artificially by injecting antibodies