Immune System

Innate/Nonspecific Immunity

The immune system's nonspecific defense mechanisms that aim to prevent pathogen entry or kill pathogens that have entered the body.

Phagocytes

A class of cells that can engulf and destroy pathogens through phagocytosis.

Neutrophils

The most common type of phagocyte that is fast and abundant, primarily responsible for phagocytosing bacteria and fungi.

Macrophages

Phagocytes that phagocytose debris and microorganisms, and also play a role in activating other immune cells.

Mast Cells

Cells found in mucous membranes and connective tissues that release cytokines and granules to initiate the inflammatory response.

Eosinophils

Granulocytes that attack multicellular parasites and can also phagocytose. They use toxic proteins and free radicals to cause tissue damage.

Basophils

Granulocytes that attack multicellular parasites and release histamine, similar to mast cells, in the allergic response.

Natural Killer (NK) Cells

Cells that destroy infected host cells to prevent the spread of infection, but do not directly attack pathogens.

Dendritic Cells

Antigen-presenting cells located in tissues that identify threats and act as messengers for the rest of the immune system via antigen presentation.

Complement System

A mechanism made up of various proteins that complements the immune response by opsonizing pathogens, attracting immune cells through chemotaxis, lysing cells, and agglutinating pathogens.

Opsonization

The process of marking foreign particles for phagocytosis.

Adaptive Immune response

activated by exposure to pathogens and uses immunological memory to learn about the threat and enhance immune response

Lymphocytes

white blood cells that make up B-cells and T-cells

B-cell

a type of lymphocyte that contains antibodies on cell surface that recognize specific pathogens

Memory B-cell

contains specialized antibodies to quickly eliminate specific pathogen if it reenters the body (stays dormant until detection)

made in bone marrow

Plasma/Effector B-cell

antibody factories that actively produces and secretes antibodies that can uniquely bind to infecting pathogens (causes clustering, inhibition of pathogen function, and opsonization)

Helper T-cells/CD4 cells

made in bone marrow but mature in thymus

binds to antigen/MHC II complex to alert immune system to produce antibodies specific to bound antigen

Killer/Cytotoxic T-cells/CD8

made in bone marrow but mature in thymus

bind to MHC 1 to kill host cell that displays antigen markings on MHC 1

Cytokine T-cells

release cytokines which strengthens/amplifies immune response to activate CH8 and b-cells

Effector T-cells

activate b-cell proliferation and differentiation

Regulatory T-cells/CD25

distinguishes between self and non-self molecules, reducing the risk of autoimmune disease

Negative Selection

tests for self tolerance and binding capabilities of CD4 and CD8 cells

eliminates cells that bind to self-molecule with no foreign antigens or contains self-antigens

Positive Selection

tests MHC detection between self and non-self molecules

T-cells that bind to non-self MHC’s are eliminated

How does the immune system know not to attack itself?

immature B-cells in the bone barrow are eliminated if they bind to any self molecules/structures

immature t-cells in the thymus undergo positive and negative selection

What are autoimmune diseases

diseases that arise when the immune system attacks normal body cells or proteins, treated with immunosuppressants

What are antibodies?

also called immunoglobulins, they are specific proteins that bind to antigens and is involved in humoral immunity

IgM

found in blood and on b-cell surface and is involved in the initial immune response

IgG

found in blood, involved in ongoing immune response

most common antibody found in blood

can cross placental barrier

IgD

found on b-cell surface and serves as an antigen receptori

IgA

found in secretions and helps protect newborns when secreted in breast milk

IgE

found in blood and is involved in allergic reactions

APCs

cells that have MHC II such as macrophages and b-cells

Primary immune response

takes weeks and occurs the first time a person encounters an antigen during an infection

presents symptoms of infection due to slow proliferation of b-cells and antibodies

Secondary immune response

occurs when the person is exposed to the same antigen

symptoms never develop and person is said to be ‘immune’

swifter and stronger immune response