Immunity Innate and Adaptive Immunity - PowerPoint Presentation

Slide1

Immunity

Innate and Adaptive Immunity

Cells of the Immune System

Physical & Chemical BarriersSlide2

Innate and Adaptive Immunity

Innate Defenses

Nonspecific physical and chemical barriers that contribute to resistance against infection

Does not exhibit immunological memory

Mediated several classes of cells and tissues, with close interactions with the adaptive responseSlide3

Innate and Adaptive Immunity

Adaptive Immunity

Response to specific biochemical groups that distinguishes between “self” and “nonself”

Antigen: Any substance that the adaptive immune system responds to

Exhibits “immunological memory:” Once the immune system has been exposed to an antigen, the response in subsequent exposures is much faster and stronger

Mediated by lymphocytesSlide4

Cells of the Immune System

Monocytes and macrophages

Function as phagocytic cells

Typically have round or horseshoe-shaped nuclei

Monocytes circulate in the blood & lymph; macrophages are derived from monocytes that have moved from the blood & lymph into surrounding tissue

Both are active as phagocytesSlide5

Cells of the Immune System

Polymorphonuclear

granulocytes

Irregular-shaped nuclei and cytoplasm with vesicles (granules) filled with hydrolytic enzymes

Neutrophils

: Function primarily as phagocytes

Eosinophils

: Function by degranulation in response to larger parasites

Basophils

: Also function predominantly by degranulation; similar to mast cells and releases histamineSlide6

Cells of the Immune System

Dendritic Cells

A class of phagocytes associated with tissues in contact with the external environment, such as skin, mucous membranes, & the intestinal lining

Dendritic cells act as “antigen-presenting cells” - they phagocytize targets such as bacteria, process the bacterial antigens and “present” them to lymphocytesSlide7

Cells of the Immune System

Lymphocytes

Responsible for the adaptive immune response

Each lymphocyte cell possesses a receptor that can bind to a specific molecular group on an antigen

There are believed to be millions of different receptor specificities, but each lymphocyte only expresses a single type of receptor on its surfaceSlide8

Cells of the Immune System

Lymphocytes

Primary lymphocytes are lymphocytes that have never responded to antigen

Primary lymphocytes respond to antigen by clonal selection, clonal expansion, and differentiation into effector cells and secondary (memory) lymphocytes

Secondary lymphocytes are able to respond more rapidly and effectively to subsequent exposures to the antigenSlide9

Cells of the Immune System

Lymphocytes

Two classes of lymphocytes: T lymphocytes and B lymphocytes

B lymphocytes

formed in the bone marrow of mammals or the Bursa of Fabricus in birds

during an immune response, B lymphocyes differentiate into plasma cells that secrete antibody protein specific for the antigen(s) encounteredSlide10

Cells of the Immune System

Lymphocytes

T lymphocytes

formed in the thymus gland

during an immune response, T lymphocyes may differentiate into several different classes of effector cells

Helper T lymphocytes (T

H

or

CD4

+

T cells) secrete cytokines that stimulate the activity of other immune cells, including B lymphocytes and other T cells

Cytotoxic T lymphocytes (T

C

or CD8

+

T cells) destroy virally-infected cells and tumor cells, and are responsible for transplant rejection

Regulatory T lymphocytes (T

reg

cells) help to mediate immunotoleranceSlide11

Physical & Chemical Barriers

Skin Barrier

Mucous membranes

Lysozyme

Antibacterial enzyme found in tears

Complement

A series of proteins in the blood and tissue fluid that can mediate cytolytic processes

Inflammation

Activation of immune cells in a damaged or infected region causes vasodilation, chemotaxis of leukocytes into the region, and diapedesis (movement of leukocytes from the capillaries into the surrounding tissue)Slide12

Physical & Chemical Barriers

Antibodies (

Immunoglobulins

)

Proteins secreted from plasma cells (which have differentiated from B lymphocytes)

5 different classes of

immunoglobulins

:

IgM

: Represents the cell-surface receptor on B lymphocytes; also is the first

Ig

to be secreted in a primary immune response

IgD

: A minor

Ig

IgG

: The major immunoglobulin found in blood & tissue fluid

IgA: Found in secretions such as saliva and breast milk

IgE

: Stimulates mast cells & causes them to release histamineSlide13

Physical & Chemical Barriers

Antibodies (

Immunoglobulins

)

Antibody structure

Two light chains

Two types,

κ

and

λ

Two heavy chains

Five different types:

μ

,

δ

,

γ

,

α

, and

ε

Class specific

Each heavy and light chain has two regions

Variable region

Constant region

http://en.wikipedia.org/wiki/AntibodySlide14

Physical & Chemical Barriers

Antibodies (

Immunoglobulins

)

Antibody molecules bind with great specificity and affinity to the antigen that originally activated the B lymphocyte

Each antibody molecule has two or more sites for binding antigen, so antigen molecules can be cross-linked, as in precipitation or

aggluttination

reactions

Antibodies play a number of essential roles in an effective immune responseSlide15

Physical & Chemical Barriers

Antibodies (Immunoglobulins)

Roles of Antibodies

Precipitation: Clumping and precipitation of soluble antigens

Agglutination: Clumping together of cellular antigens

Virus neutralization

Toxin neutralization

Complement fixation: Antibody molecules can trigger a complement pathway leading to the lysis of a cellular antigen

Opsonization: Antibody molecules can coat a cellular antigen, making it much easier for a phagocyte to recognize and engulf